Zero‑dimensional modelling of˜a˜f‑cylinder turbocharged ... · Zero‑dimensional modelling...
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Vol.:(0123456789) SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x Research Article Zero‑dimensional modelling of a four‑cylinder turbocharged diesel engine with variable compression ratio and its effects on emissions Daniyal Khan 1 · M. Zafer Gül 2 © Springer Nature Switzerland AG 2019 Abstract With emission legislation becoming ever more stringent, declining fossil resources and an increase in greenhouse effect caused by CO 2 emissions, manufacturers are exploring new ways to match the emissions regulations without com- promising on the performance of the engine. This study included development of zero-dimensional model of a 2.0 L turbocharged diesel engine and then study the effects of changing its compression ratio in the numerical model. This paper gave a framework in determining the effect of compression ratios in different operational conditions of the engine. Implementation of variable compression ratio technology on a numerical model proved to be very cost-effective, time saving and validated the fact that numerical models can be used to study different parameters of the engines during the development stage. The main effect of an increase in compression ratio, was found to be as expected, a decrease in brake specific fuel consumption and an increase in thermal efficiency with a greater impact at low rpm-low load regions. Assum- ing, that the variable compression ratio technology can be utilized in the engine, this work found the best combination of compression ratios around the engine map, giving a best fit of trade-offs between the emissions and performance of the engine. This study also validates the fact that variable compression ratio technology, if implemented in the engine could not only reduce emissions of the engine but can be given as an option to the end-user to switch to more economic fuel consumption values during idling or cruising at long distant journeys. Keywords Internal combustion engine · Variable compression ratio · Numerical modelling · Combustion · Emissions · Zero dimensional Abbreviations BDC Bottom dead centre BMEP Brake mean effective pressure BSFC Brake specific fuel consumption CA Crank angle CAC Charge air cooler CO Carbon monoxide CO 2 Carbon dioxide DAC Digital analogue convertor DI Direct injection DPF Diesel particulate filter EAS Exhaust aftertreatment system ECU Electronic control unit EGR Exhaust gas recirculation HC Hydrocarbons HCCI Homogeneous charge compression ignition HiL Hardware in the loop HP High pressure IMEP Indicated mean effective pressure LNT Lean NOx trap MD Torque ME Mechanical efficiency MF_Fuel Mass flow of fuel MF_IA Mass fuel of intake air MFB50% Mass fuel burnt 50% MiL Model in the loop MoBEO Model based engine optimization N Engine speed Received: 21 May 2019 / Accepted: 28 August 2019 / Published online: 5 September 2019 * Daniyal Khan, [email protected] | 1 AVL List GmbH, Graz, Austria. 2 Mechanical Engineering Department, Marmara University, Istanbul, Turkey.
Transcript of Zero‑dimensional modelling of˜a˜f‑cylinder turbocharged ... · Zero‑dimensional modelling...
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Research Article
Zero‑dimensional modelling of a four‑cylinder turbocharged diesel engine with variable compression ratio and its effects on emissions
Daniyal Khan1 · M. Zafer Gül2
© Springer Nature Switzerland AG 2019
AbstractWith emission legislation becoming ever more stringent, declining fossil resources and an increase in greenhouse effect caused by CO2 emissions, manufacturers are exploring new ways to match the emissions regulations without com-promising on the performance of the engine. This study included development of zero-dimensional model of a 2.0 L turbocharged diesel engine and then study the effects of changing its compression ratio in the numerical model. This paper gave a framework in determining the effect of compression ratios in different operational conditions of the engine. Implementation of variable compression ratio technology on a numerical model proved to be very cost-effective, time saving and validated the fact that numerical models can be used to study different parameters of the engines during the development stage. The main effect of an increase in compression ratio, was found to be as expected, a decrease in brake specific fuel consumption and an increase in thermal efficiency with a greater impact at low rpm-low load regions. Assum-ing, that the variable compression ratio technology can be utilized in the engine, this work found the best combination of compression ratios around the engine map, giving a best fit of trade-offs between the emissions and performance of the engine. This study also validates the fact that variable compression ratio technology, if implemented in the engine could not only reduce emissions of the engine but can be given as an option to the end-user to switch to more economic fuel consumption values during idling or cruising at long distant journeys.
Keywords Internal combustion engine · Variable compression ratio · Numerical modelling · Combustion · Emissions · Zero dimensional
AbbreviationsBDC Bottom dead centreBMEP Brake mean effective pressureBSFC Brake specific fuel consumptionCA Crank angleCAC Charge air coolerCO Carbon monoxideCO2 Carbon dioxideDAC Digital analogue convertorDI Direct injectionDPF Diesel particulate filterEAS Exhaust aftertreatment systemECU Electronic control unitEGR Exhaust gas recirculation
HC HydrocarbonsHCCI Homogeneous charge compression ignitionHiL Hardware in the loopHP High pressureIMEP Indicated mean effective pressureLNT Lean NOx trapMD TorqueME Mechanical efficiencyMF_Fuel Mass flow of fuelMF_IA Mass fuel of intake airMFB50% Mass fuel burnt 50%MiL Model in the loopMoBEO Model based engine optimizationN Engine speed
Received: 21 May 2019 / Accepted: 28 August 2019 / Published online: 5 September 2019
* Daniyal Khan, [email protected] | 1AVL List GmbH, Graz, Austria. 2Mechanical Engineering Department, Marmara University, Istanbul, Turkey.
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NO Nitrogen oxideNOx Oxides of nitrogenNTE Not-to-exceedP_EO Pressure at engine outPFP Peak firing pressurePID Proportional–integral–derivativeQWHT Wall heat transferRDE Real driving emissionsRPM Revolutions per minuteROHR Rate of heat releaseSCR Selective catalytic reductionSFC Specific fuel consumptionSiL Software in the loopSOC Start of combustionSVC SAAB variable compressionT_EO Temperature at engine outTDC Top dead centreTHC Total hydrocarbonsVCR Variable compression ratioVGT Variable geometry turboVNT Variable nozzle turbineVVT Variable valve timing
1 Introduction
With emission legislation becoming ever more stringent, declining fossil resources and an increase in greenhouse effect, manufacturers are exploring new ways to match the emissions regulations without compromising on the performance of the engine. A “Not-To-Exceed” zone is also being introduced as a part of these legislations, where tail pipe emissions must not exceed a specific value. Legis-lations like these break the stronghold of keeping these engines economical under the same performance circle. Although new technologies like the control methods, exhaust gas recirculation (EGR), and variable valve timing (VVT), have helped to reduce the NOx and soot emissions considerably [1–8], further measures are to be taken to meet the increasingly restrictive emission standards.
It is of no contradiction that diesel engines are in the top list to face emission limitations in near future and the trade-offs between NOx–CO2–Soot emissions must be handled without compromising on the performance out-puts [9, 10].
Several techniques and methodologies have been introduced in making combustion leaner and lower the emission levels. One way to reduce these pollutant emis-sions is using the technology called homogenous charge compression ignition (HCCI) combustion. It consists of preparing a highly homogenous air/fuel mixture that will result in a homogenous and efficient in-cylinder com-bustion. Thus, a complete and controlled combustion
would mean better performance, lower emissions and above all no soot is produced [11].
Among many other factors, compression ratio is a direct influencer on the performance of the engine. In engines, a fixed compression ratio over the whole load and rpm range caps a limit on its operational efficiency and emissions over different regions. In conventional engines, a fixed compression ratio is selected which suc-cessfully operates it at variable rpms and loads mean-while achieving a reliable self-ignition when starting the engine at cold-start.
The real problem is the fact that a fixed compression ratio of internal combustion engine is not optimal for all operating conditions. It is normally set as a compromise between partial and full-load requirements. A very high compression ratio could improve high part-load effi-ciency but will result in a knock (gasoline engines) and peak pressure limitations in diesel engines. An engine a fixed with low compression ratio provides performance with low maximal cylinder pressure which in turn means low frictional losses, costs and weight of the engine but limits the maximum achievable torque. An engine like this requires a glow plug which gives it a cold start ability resulting in a more stable idle operation and less smoke [11–14]. Therefore, the new technology of variable com-pression ratio (VCR) offers more flexibility in terms of controlling power and emissions at different operating load conditions.
Turbocharged diesel engines are usually also restricted by the stress levels in moving mechanical components. With an increase in boost pressure, maximum pressure, thermal loading and friction losses also increase pro-portionally, unless engine design and operating condi-tions are changed. Practically, compression ratio is often reduced in turbocharged engines to maintain peak pres-sures and thermal loading at acceptable levels [15].
VCR technology could not provide a cold-start ability but also could change the engine’s combustion capability in such a way to get the optimal trade-offs of emissions, performance and fuel consumption at desired rpm and loads [16]. Different VCR methodologies implemented in the industry are also critically being examined to under-stand its applications and scope and a thorough study in this context can be found in [17].
A study comparing the experimental results with numerical modelling results was performed before in [18]. But as per our knowledge, no previous study has been done comprising of a detailed model especially imple-menting VCR directly in the numerical model and compar-ing the performance parameters in terms of engine maps.
According to theoretical studies, the overall efficiency of internal combustion engines can be improved: up to 40% for otto and up to 50% for diesel engines. Efficiency
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of over 50% is achieved only by two-stroke marine diesel engines [19, 20].
Early stage calibration is a way to assure meeting of the emission requirements at various ambient conditions while still delivering the desired engine performance and fuel consumption. In this process the major concern always remains to find the optimal compromise between emission, performance and fuel consumption targets under all ambient conditions and to achieve this with very limited access to non-standard engine tests beds.
Modern numerical models and tools help to pre-cali-brate these engine correction functions at a virtual test-bed embedded with numerical models of the engine. This delivers an identical environment as on real testbeds, while saving time and money. With emission standards becoming narrower every day, these simulation tools can prove to be very effective in development process to meet the standard called real driving emission (RDE). The vir-tual test-bed is setup with high precision empirical and physical models/components to simulate the real working of the engine under different scenarios as accurately as possible. This widely helps in combustion refinement and pre-optimizing the thermodynamic cycle of the engine.
‘Concept-to-Road’ calibration is therefore considered an important part of the pre-prototyping phase. A baseline requirement of numerical validation is based on data of the base model of the engine from real testbed. Therefore, numerical modeling tools play a crucial part in the opti-mization and validation of the powertrain development process providing a very swift and cost-effective way at the early development stages, before even the prototype becomes available.
2 Objectives
The aim of this work is to develop a zero-dimensional numerical model of a 2.0 L four-cylinder turbocharged die-sel engine in AVL Cruise-M (MoBEO-model based engine optimization) [21] which will then be simulated with VCR technology to understand the effect of this technology on the performance and emissions of the engine.
Modelling of the thermodynamic cycles of the engine is very easy and understandable. However, these cycles become more complex when combustion refinement is being performed by tuning various parameters of the engine. Thus, there are limits to which these parameters can be altered in the thermodynamic processes. The influ-ence of compression ratios on the changes in thermody-namic combustion process in an engine has been studied in [10] and is considered while modelling the engine.
The first part of this study will focus on the method-ologies for correlating dynamic simulations with any
performance parameter in the dynamic engine opera-tion with insights on the emissions data. This correlation can be performed using simulated test runs within AVL’s mean value engine model, MoBEO. Using this approach, the main objective will be to explain how the correlated engine values and the small differences between measure and simulated results can be sourced by specific dynamic phenomena and how they impact the obtained results. It will also help to understand that having a correlation between the model and measurement data, can help in achieving front-load calibration with a very high level of confidence. This study will also summarize the factors which are influenced by changing compression ratio in diesel engine, which may be used in developing a strategy towards the concept of ‘One Engine for all fuels or One Fuel for all engines’ [22].
This work can help in developing an industrial approach towards zero-dimensional numerical model of a real engine and could add to the confidence on relying at such models. One of the main aims of the work is also to show the load conditions of the engine terms of various regions on engine maps. This would help in framing the zones in the engine map where VCR technology has the maximum and minimum effect on the emissions and performance of the engine. An optimal compression ratio specific to each region can also be suggested through this process.
Effects of several operating parameters will also be studied using the obtained results which can act as a solid rung towards showing the strategies to be utilized for fur-ther studies.
2.1 Zero‑dimensional modelling approach
Cruise-M was used to create the numerical model of the engine. MoBEO is a tool developed by AVL GmbH which integrates empirical and physical models. This means that the airpath of the modelled engine was fully physical whereas, the cylinder model was based on semi-physical modeling approach as can also be seen in Fig. 5. Instead of complex cylinder configurations, MoBEO enables ‘concept model capability’—tune the cylinder using fit-parameters based on ten thousand of engine test bed measurements. Thus, it demands 25 basic cylinder and fueling parameters measured from the testbed in order to perform the com-bustion refinement based on previously embedded data. Emission models are a part of this semi-physical approach. More details regarding the empirical, semi-physical and physical based models used by MoBEO can be accessed from [21].
A numerical diesel engine generally deals with mean engine values of performance and emission parameters (pressures, flow rates, temperatures, boundary conditions etc.). Moreover, the aftertreatment system can also be
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integrated and dealt in detail within the model. Since the complexity of the engine increases when testing change of compression ratios on physical testbeds, a numerical approach to study the trending technology of VCR can be useful in validating the circumstances which give the opti-mal trade-off of performance and emissions. One of the most vital advantage of engine modelling is the cut-off in both costs and time. Virtual test beds with engine models can save a lot of expenses that could otherwise incur dur-ing modification and testing process on real testbeds.
Numerical models cannot always replace the test-bed engine testing but could produce very close estimates
of changes in the operational conditions, emissions and performance. This vastly helps in predicting the relevant parameters and selecting the best case during the engine development stage.
Basis of powertrain engineering is to enable a rapid setup of numerical model and to use it in a wide variety of applications. The engine domain is the heart of the entire multi-disciplinary model-based development solution. This becomes possible because of dedicated numerical solvers that work at explicit constant time step and implicit adaptive time step integration using transient and steady-state zero-dimensional component models. A steady-state approach is normally applied in modelling the basic flow characteristics. Numerical models are not only capable of being faster than real-time but also support a very high amount of cycle simulations with different hardware vari-ants. They are also capable of transient system operation
Fig. 1 Energy balance of the combustion chamber
Fig. 2 Infiniti VC-T technology [20]
Table 1 Engine specifications
Type Four-stroke diesel
Displacement 2.0 L (1996 cc)Bore length 84 mmStroke length 90 mmNumber of turbochargers Single stage turbochargedType of turbocharger Variable geometry turbochargerNumber of cylinders In-line four cylindersFuel injection type Direct in-cylinderInjections One pilot and one mainCompression ratio 16.5rated power 125 kW @ 3500 rpmMax torque/speed range 405 Nm @ 1750–2500 rpmIdle engine speed 840 rpmMaximum engine speed 5100 rpm
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
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Fig. 3 Log points of measurement data collected from testbed
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which makes it easier to study stochastic changes of the engine and exhaust gas aftertreatment system.
2.2 Single zone combustion model
There are several textbooks that explain the main prin-ciples of operations of internal combustion engine. One book which discusses most aspects of internal combus-tion engines is [23]. The conservation equations of all the models basically comprise of mass, energy and species balances. The basic idea of the energy split in the com-bustion chamber is sketched in Fig. 1.
The calculation of the thermodynamic state of the cyl-inder is based on the first law of thermodynamics:
where mc is mass in the cylinder, u is specific internal energy, pc is cylinder pressure, V is cylinder volume, α is crank angle, QF is fuel energy, Qw is wall heat loss, dmi is mass element flowing into the cylinder, hi is specific enthalpy of the in-flowing mass, dme is mass element flow-ing out of the cylinder, he is enthalpy of the mass leaving the cylinder, qev is evaporation heat of the fuel, f is fraction of evaporation heat from the cylinder charge and mev is evaporating fuel.
2.3 Variable compression ratio
There are three direct methodologies through which an efficient combustion can be achieved in the engine: downsizing, supercharging and varying the compression ratio [24].
(1)
d(
mc ⋅ u)
d�= −pc ⋅
dV
d�+
dQF
d�−∑ dQw
d�
+∑ dmi
d�⋅ hi −
∑ dme
d�⋅ he − qev ⋅ f ⋅
dmev
d�
Fig. 4 Standalone model in AVL Cruise-M
Fig. 5 Full engine model in AVL Cruise-M
Fig. 6 VCR simulation setup in MoBEO
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MD
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Fig. 7 Difference in brake torque
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Fig. 8 Difference in mass flow of intake air
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Fig. 9 Difference in engine out NOx
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Fig. 10 Difference in brake mean effective pressure
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Fig. 11 Difference in brake specific fuel consumption
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Fig. 12 Difference in intake pressure
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Fig. 13 Difference in boost pressure
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Varying the compression ratio in a running engine is a new technology that has been developed called vari-able compression ratio, which radically improves the fuel consumption without impairing engine performance at certain regions of the engine map. VCR engines have been categorized into several classes in [25].
Compression ratio, rc, is generally defined as:
where Vd is the displaced volume and Vc is the clearance volume. In other words, the amount by which the fuel/air mixture is compressed in the cylinder before it is ignited. Among the other factors, compression ratio of an engine is one of the most important factors that determine how efficiency an engine could utilize the energy in the fuel.
VCR is a technology which directly changes the com-pression ratio of the engine by changing the stroke under
(2)rc =Vd + Vc
Vc
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Fig. 14 Difference in intake manifold pressure
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Fig. 15 Difference in engine out pressure
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Fig. 16 Difference in boost temperature
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Fig. 17 Difference in temperature at intake manifold
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-10
-10
-10
55
5
5
5
20
20
-20
-15
-10
-5
0
5
10
15
20Delta T_31 [°C]
Fig. 18 Difference in temperature at engine exhaust manifold
Vol:.(1234567890)
Research Article SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x
the same operating conditions. This phenomenon diver-sifies the engine to adjust its compression ratio directly according the load and performance need. Diesel engines have high thermal efficiencies as compared to gasoline engines mainly because of their higher compression ratios. As compression ratio decreases, both the gas pressure and temperature decrease at the end of compression stroke,
thus it has a very critical influence on the combustion pro-cess and ultimately the performance of the engine.
For an ideal Diesel cycle the theoretical efficiency is:
where γ is ratio of specific heats (1.4 at ambient tempera-ture), rv is compression ratio of the engine and rc is the cut-off ratio.
Diesel engines normally have compression ratios between 14:1 to 25:1. Higher compression ratios mean a higher thermal efficiency, which means that theoreti-cally maximum efficiency can be achieved at an infinite compression ratio. However, a high compression ratio results in higher cylinder pressures and temperatures which limit it to a certain value.
A higher compression ratio also results in an increase in frictional losses and lowers down the mechanical effi-ciency [10]. Furthermore, it also increases heat transfer to the combustion chamber walls due to small clearance vol-ume resulting in a very high temperature gradient. High compression ratio also comes with shortened ignition
(3)�th = 1 −r1−�v
(
r�
c − 1)
�
(
rc − 1)
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
5
5
908743235941
957445
697
365
084
0
41.37641.34339.3536.73132.958
23.69712.412
5.914
0.049
00
35.13834.53333.37
29.97625.57421.37118.179
12.338
8.846
0.048
0.007
0.0060.0910.027
0.0810.016
33.95133.17430.43725.44221.182
18.798
16.764
14.307
11.711
11.138
5.762
3.665
6.579
0
0.014
-0.006
00
26.70525.39820.248
17.3
17.58
15.79
12.538
11.199
10.26
7.339
2.608
2.499
0.004
0
0-0.001
22.0521.43418.268
17.59716.063
14.272
14.025
10.686
7.982
2.77
2.187
1.4
4.029
0.2940
00
19.94219.72117.331
17.43116.39914.587
12.822
10.97
8.364
7.5
6.379
6.733
6.487
4.342
2.75
0.27
19.88518.7117.24
17.919
16.48114.216
12.107
9.868
8.65
8.846
8.116
7.967
8.185
7.425
5.773
0.453
0.481
17.36216.87515.85
16.054
16.804
12.545
10.298
7.899
8.934
8.232
8.604
8.351
8.298
6.52
1.824
0.329
18.29616.56313.63616.233
15.435
9.945
8.444
8.672
7.601
8.149
7.884
7.8
0.012
0.129
13.51213.49212.29
11.818
12.74
9.417
7.864
6.643
6.578
4.957
0.039
0.0060.017
0.063
12.18312.3712.236
9.613
10.522
7.187
6.576
6.747
5.511
0
0.028
0
0
00
11.496
12.185
7.739
10.222
8.235
7.842
7.323
2.651
0.008
00
0.003
0
0
0.03
0.0070
0.012
0.014
0.009
0.010.016
0
0
0
00
0
0
00
0.4
-10-7.5-5-2.502.557.510
Fig. 19 Percentage massflow of EGR as compared with total mass-flow
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
948278586059
004796
843
332
585
414
48.18230.16829.82226.08323.61
13.189.956
8.729
7.345
5.2593.721
34.37328.77423.50420.60518.56
15.7669.757
6.522
5.462
3.89
3.654
2.9883.1322.949
1.7781.822
36.47329.96825.39621.27115.559
12.649
8.568
7.841
5.699
4.598
3.291
2.648
2.716
2.418
2.689
2.164
1.631.547
22.03325.09721.489
10.281
7.722
6.977
5.196
3.727
2.913
2.316
1.407
1.383
2.079
1.708
0.970.853
22.68119.63315.036
12.0488.331
7.045
5.151
4.071
3.15
2.4
2.041
1.764
1.813
1.6271.984
1.8311.649
25.4424.55
18.027
10.7358.7667.458
5.348
3.439
3.157
2.559
2.591
2.265
2.056
1.712
2.009
1.793
16.54716.19513.466
8.755
8.0886.087
4.911
4.467
3.697
3.119
2.912
2.676
2.577
1.891
1.8
1.782
1.569
11.9310.4678.619
7.155
5.994
4.578
4.311
4.339
3.857
3.63
2.818
2.154
2.007
1.706
1.492
1.355
9.8569.4168.38
5.915
3.467
3.218
3.337
3.91
2.977
2.498
1.598
1.466
1.682
1.758
7.5196.9787.2586.453
3.644
2.663
3.133
2.422
2.306
1.652
1.383
1.1911.278
0.925
4.4114.7455.507
5.035
3.247
3.081
2.482
2.402
2.268
2.137
1.533
1.329
1.517
1.8681.698
1.869
2.998
2.398
2.424
2.43
1.876
1.875
2.083
1.83
1.9271.761
1.629
1.545
1.922
1.495
1.5232.872
1.265
1.967
1.821
1.5011.199
1.092
1.32
1.19
1.3382.49
1.519
1.266
0.9040.824
0.8
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
623986304394
915297
422
41
443
617
19.17111.99511.505
9.929.252
5.2693.969
3.735
2.567
1.952.086
13.58611.3869.0637.8266.9876.1613.858
2.657
2.331
1.614
1.461
1.261.3041.197
0.8870.912
13.911.1089.3698.0375.838
4.867
3.335
3.038
2.208
1.797
1.298
1.055
0.951
0.822
1.024
0.893
0.5460.56
7.7939.0847.935
3.917
2.88
2.431
2.348
1.406
1.148
0.93
0.565
0.616
0.946
0.648
0.4240.406
8.2567.0985.604
4.7952.997
2.561
2.003
1.577
1.237
0.915
0.854
0.735
0.676
0.7050.634
0.7360.606
8.9188.3636.327
3.7043.2862.661
1.989
1.345
1.154
0.913
0.903
0.843
0.675
0.641
0.694
0.596
5.595.3784.619
2.948
2.8122.295
1.69
1.546
1.327
1.039
0.995
0.951
0.841
0.689
0.616
0.627
0.558
3.8833.3892.785
2.238
1.987
1.636
1.429
1.419
1.26
1.179
0.958
0.716
0.716
0.592
0.522
0.483
2.1682.7852.5641.89
1.125
1.065
0.996
1.354
0.947
0.81
0.524
0.504
0.532
0.554
1.8691.8442.0791.93
1.141
0.852
0.908
0.755
0.712
0.566
0.432
0.390.419
0.318
0.8731.07
1.452
1.479
0.958
0.928
0.712
0.711
0.681
0.654
0.457
0.345
0.438
0.5540.505
0.126
0.575
0.58
0.667
0.661
0.514
0.523
0.577
0.514
0.5090.482
0.438
0.125
0.424
0.333
0.4120.701
0.321
0.462
0.565
0.3940.345
-0.155
0.111
0.211
0.2810.538
0.437
0.289
0.1980.167
0.1
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
836781.14187
525963
017
567
543
543
-15.43-12.456-11.046-8.938-7.868
-4.912-3.819
-3.688
-2.356
-2.294-2.261
-12.47-10.315-8.106-6.65-5.964-5.28-3.867
-2.59
-2.277
-1.657
-1.333
-1.238-1.236-1.195
-1.074-1.051
-12.411-9.534-7.967-6.99-5.141
-4.249
-3.113
-2.37
-2.069
-1.523
-1.198
-1.035
-0.78
-0.559
-0.873
-0.755
-0.643-0.509
-6.678-7.517-6.718
-3.551
-2.445
-2.027
-2.106
-1.261
-1.036
-0.969
-0.636
-0.706
-0.316
-0.823
-0.833-0.817
-6.817-5.38-4.692
-4.077-2.622
-2.141
-1.735
-1.429
-1.15
-0.838
-0.876
-0.631
-0.612
-0.589-0.2
-0.548-0.151
-4.793-6.312-5.01
-2.985-2.766-2.185
-1.668
-1.164
-1.002
-0.825
-0.723
-0.702
-0.536
-0.536
-0.55
-0.431
-4.283-3.867-3.504
-2.302
-2.769-1.872
-1.372
-1.255
-1.067
-0.837
-0.752
-0.752
-0.609
-0.536
-0.49
-0.489
-0.455
-2.811-2.441-2.035
-1.483
-1.487
-1.3
-1.111
-1.091
-0.968
-0.899
-0.724
-0.542
-0.567
-0.463
-0.425
-0.383
-1.443-1.87-1.843-1.36
-0.831
-0.837
-0.728
-0.999
-0.705
-0.6
-0.413
-0.387
-0.42
-0.429
-1.033-1.084-1.398-1.319
-0.855
-0.661
-0.488
-0.548
-0.517
-0.466
-0.332
-0.305-0.337
-0.269
-0.275-0.49-1.165
-1.019
-0.717
-0.667
-0.487
-0.501
-0.47
-0.466
-0.334
-0.269
-0.313
-0.386-0.356
0.16
-0.189
-0.405
-0.477
-0.46
-0.343
-0.322
-0.38
-0.35
-0.325-0.314
-0.279
0.059
-0.251
-0.252
-0.326-0.459
-0.204
-0.264
-0.344
-0.236-0.222
0.468
0.009
-0.148
-0.192-0.29
-0.258
-0.148
-0.094-0.078
-0.0
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
174821354448
8.4181
788
957
601
172
-34.977-26.83-25.865
-19.658-16.799
-11.048-8.719
-8.331
-5.345
-5.868-5.645
-28.069-22.967-18.349-14.518-12.651-11.566-9.162
-5.676
-5.143
-3.774
-2.9
-2.759-2.779-2.787
-2.431-2.404
-27.345-20.716-17.146-15.263-11.259
-9.11
-6.978
-5.139
-5.221
-3.461
-2.809
-2.389
-1.888
-1.822
-1.92
-1.675
-1.567-1.381
-14.411-13.955-13.452
-7.881
-5.343
-4.422
-4.709
-2.805
-2.341
-2.132
-1.498
-1.665
-0.257
-1.754
-0.556.615
-14.511-11.289-10.016
-8.9-5.924
-4.688
-3.824
-3.278
-2.647
-1.88
-1.955
-1.342
-1.302
-1.321-0.988
-0.95-0.264
-13.247-12.981-10.379
-6.329-5.883-4.658
-3.59
-2.491
-2.285
-1.811
-1.569
-1.565
-1.215
-1.242
-1.02
-0.812
-10.017-7.951-7.197
-3.957
-5.78-3.951
-2.907
-2.655
-2.346
-1.744
-1.553
-1.606
-1.246
-1.122
-1.036
-1.032
-0.976
-6.802-4.858-4.206
-3.135
-3.152
-2.794
-2.346
-2.292
-1.983
-1.866
-1.495
-1.122
-1.173
-0.976
-0.894
-0.824
-2.88-3.836-3.794-2.848
-1.704
-1.804
-1.476
-2.067
-1.452
-1.25
-0.856
-0.802
-0.883
-0.909
-1.997-2.17-2.906-2.728
-1.83
-1.419
-1.008
-1.128
-1.072
-0.947
-0.698
-0.644-0.754
-0.587
-0.948-0.982-2.468
-2.152
-1.498
-1.418
-1.002
-1.028
-0.959
-0.946
-0.695
-0.574
-0.65
-0.792-0.732
0.229
-0.502
-1.148
-1.118
-1.024
-0.919
-0.567
-0.783
-0.709
-0.645-0.626
-0.547
0.006
-0.676
-0.679
-0.834-1.054
-0.447
-0.511
-0.65
-0.453-0.45
0.889
-0.167
-0.488
-0.544-0.645
-0.48
-0.301
-0.194-0.167
-0.0
-10-7.5-5-2.502.557.510
Fig. 20 Mass flow of fuel as compared with CR16.5
Vol.:(0123456789)
SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x Research Article
delays as both pressure and temperature in the cylinder increase during fuel injection. Moreover, not only the weight and cost of the engine increases but it also intro-duces more complexity, frictional losses and unburnt hydrocarbons. Theoretically, the brake thermal efficiency increases with an increase in compression ratio, reaches an optimal maximum value and does not show any further increase after a certain compression ratio value.
In conventional engines, the minimum compression ratio is calculated such that it supports the start of engine with little amount of fuel (very low load operation) or cold start (when temperatures are below 0 °C). Starting from that minimum compression ratio, a single compression ratio value is then determined which gives a perfect trade-off between the emissions and performance at different operational conditions. One of the important facts is that diesel engines do not run at the same loads. For instance, at a long-distance motorway journey, the engine will oper-ate at low load/idling condition while during acceleration, it will work under full load conditions.
With a VCR engine, compression ratio can be increased at start-up and low power operations to get a stable igni-tion and operation, while the compression ratio can be
lowered during high load operations to get more power by burning more fuel. Therefore, the VCR concept can be con-sidered as a very reliable solution to the problems being faced by engineers in varying the combustion conditions in the engine during different load conditions. An engine with VCR makes it possible to increase its overall efficiency, by choosing high compression ratios at low loads to maxi-mize the efficiency, and low compression ratios at high loads to avoid knock (in case of gasoline engines).
There are various patents which all correspond to real-izing the VCR technology in the engines [9]. Moreover, a VCR engine can use fuels with any cetane number under normal operation [22].
Majority of mechanical methodologies vary the volume of the combustion chamber to vary the compression ratio. For instance, Infiniti has a harmonic drive embedded with the crank shaft that varies the compression ratio between 8:1 and 14:1 as shown in Fig. 2 [20].
Volvo/Alvar engine varies the volume of the combus-tion chamber through a secondary piston in the cylinder head [26]. The constrain to this design was that since it had four valves per cylinder, supercharging was also necessary to achieve the effect completely.
CR:18 CR:20
CR:13 CR:15
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [rpm]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
32 21 10 0 0 0 0 01 1 1
1
1
1
2 2 2
2
2
3 3 34 4 45 5 56 6 67 7 778 8 8
89 9 9
99
10 10 1010491
278586059
004796
843
332
585
414
030.16829.82226.08323.61
13.189.956
8.729
7.345
5.2593.721
34.37328.77423.50420.60518.56
15.7669.757
6.522
5.462
3.89
3.654
2.9883.1322.949
1.7781.821
029.96825.39621.27115.559
12.649
8.568
7.841
5.699
4.598
3.291
2.648
2.716
2.418
2.689
2.164
1.631.547
22.03325.09721.489
10.281
7.722
6.977
5.196
3.727
2.913
2.316
1.406
1.383
2.079
1.708
0.970.853
22.68119.63315.036
12.0488.331
7.045
5.151
4.071
3.15
2.4
2.041
1.764
1.813
1.6271.984
1.8311.649
9.98724.55
18.027
10.7358.7667.458
5.348
3.439
3.157
2.559
2.591
2.265
2.056
1.712
2.009
1.793
14.67816.19513.466
8.755
8.0886.088
4.911
4.467
3.697
3.119
2.912
2.676
2.577
1.891
1.8
1.782
1.569
010.4678.619
7.155
5.994
4.578
4.31
4.339
3.857
3.63
2.818
2.154
2.007
1.706
1.492
1.355
09.4168.38
5.915
3.467
3.218
3.337
3.91
2.977
2.498
1.598
1.466
1.682
1.758
06.9787.2586.453
3.644
2.663
3.133
2.422
2.306
1.652
1.383
1.1911.278
0.925
04.7455.507
5.035
3.247
3.081
2.482
2.402
2.268
2.137
1.533
1.329
1.517
1.8681.698
0
2.998
2.398
2.424
2.43
1.876
1.875
2.083
1.83
1.9271.761
1.629
1.545
1.922
1.495
1.5222.872
1.265
1.967
1.821
1.5011.199
1.092
1.32
1.19
1.3382.49
1.519
1.266
0.9040.824
0.8
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [rpm]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
10 0 0 0 0 01 1 1
1
1
2 2 23 33
4 4
4
5 5
5
6 6
67 7 78 8 8
9 9 9
9
10 10623986304394
915297
422
41
443
617
011.99511.505
9.929.252
5.2693.968
3.735
2.567
1.952.086
13.58611.3869.0637.8266.9876.1613.858
2.657
2.331
1.614
1.461
1.261.3041.197
0.8870.912
011.1089.3698.0375.838
4.867
3.335
3.038
2.207
1.797
1.299
1.055
0.951
0.822
1.024
0.893
0.5460.56
7.7939.0847.935
3.917
2.879
2.431
2.348
1.406
1.148
0.93
0.565
0.616
0.946
0.648
0.4240.406
8.2567.0985.604
4.7942.997
2.561
2.003
1.577
1.237
0.915
0.854
0.735
0.676
0.7050.634
0.7360.606
8.9188.3636.327
3.7043.2862.661
1.989
1.345
1.154
0.913
0.903
0.843
0.675
0.641
0.694
0.596
5.595.3784.619
2.948
2.8122.295
1.69
1.546
1.327
1.039
0.995
0.951
0.841
0.689
0.616
0.627
0.558
03.3892.785
2.238
1.987
1.636
1.429
1.419
1.26
1.179
0.958
0.716
0.716
0.592
0.522
0.483
02.7852.5641.89
1.125
1.065
0.996
1.354
0.947
0.81
0.524
0.504
0.532
0.554
01.8452.0791.93
1.141
0.852
0.908
0.755
0.712
0.566
0.432
0.390.419
0.318
01.07
1.452
1.479
0.958
0.928
0.712
0.711
0.681
0.654
0.457
0.345
0.438
0.5540.505
0
0.575
0.58
0.667
0.661
0.514
0.523
0.577
0.514
0.5090.482
0.438
0.125
0.424
0.333
0.4120.701
0.321
0.462
0.565
0.3940.345
-0.155
0.111
0.211
0.2810.538
0.437
0.289
0.1980.166
0.1
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [rpm]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-10
-10-8
-8
-6 -6 -6
-4 -4-4
4
-2 -2
-2
0 0 0 0 0 0836781.14187
525963
017
567
543
543
0-12.456-11.046-8.938-7.868
-4.912-3.819
-3.687
-2.356
-2.294-2.261
-12.47-10.315-8.106-6.65-5.964-5.28-3.867
-2.59
-2.277
-1.657
-1.333
-1.238-1.236-1.195
-1.074-1.051
0-9.534-7.967-6.99-5.141
-4.249
-3.113
-2.37
-2.069
-1.523
-1.198
-1.035
-0.78
-0.559
-0.873
-0.755
-0.643-0.509
-6.678-7.517-6.718
-3.551
-2.445
-2.027
-2.106
-1.261
-1.036
-0.969
-0.636
-0.706
-0.317
-0.823
-0.833-0.817
-6.817-5.38-4.692
-4.077-2.622
-2.141
-1.735
-1.429
-1.15
-0.838
-0.876
-0.63
-0.612
-0.589-0.2
-0.548-0.151
-4.793-6.312-5.01
-2.985-2.766-2.185
-1.668
-1.164
-1.002
-0.825
-0.723
-0.702
-0.536
-0.536
-0.55
-0.431
-4.283-3.867-3.504
-2.302
-2.77-1.872
-1.372
-1.255
-1.067
-0.837
-0.753
-0.752
-0.609
-0.536
-0.49
-0.489
-0.455
0-2.441-2.035
-1.483
-1.487
-1.3
-1.111
-1.091
-0.968
-0.899
-0.724
-0.542
-0.567
-0.463
-0.425
-0.383
0-1.87-1.843-1.36
-0.831
-0.837
-0.728
-0.999
-0.706
-0.6
-0.413
-0.387
-0.42
-0.429
0-1.084-1.398-1.319
-0.855
-0.661
-0.488
-0.548
-0.517
-0.466
-0.332
-0.305-0.337
-0.269
0-0.49-1.165
-1.019
-0.717
-0.667
-0.487
-0.501
-0.47
-0.466
-0.334
-0.269
-0.313
-0.386-0.356
0
-0.189
-0.405
-0.477
-0.46
-0.343
-0.322
-0.38
-0.35
-0.325-0.314
-0.279
0.059
-0.251
-0.252
-0.326-0.459
-0.204
-0.264
-0.344
-0.236-0.222
0.468
0.009
-0.148
-0.192-0.29
-0.258
-0.148
-0.094-0.078
-0.0
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [rpm]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
10-10
10
0
-8
-8
-6-4
-2
-2
-2
0 0 0 0
0 2 468 10
174821354448
8.4181
788
957
601
172
-18.87-26.83-25.865
-19.658-16.799
-11.048-8.719
-8.331
-5.345
-5.868-5.645
-28.069-22.967-18.349-14.518-12.651-11.566-9.162
-5.676
-5.143
-3.774
-2.9
-2.759-2.779-2.787
-2.431-2.404
-9.806-20.716-17.146-15.263-11.259
-9.11
-6.978
-5.139
-5.221
-3.461
-2.809
-2.389
-1.888
-1.822
-1.92
-1.675
-1.567-1.381
-14.411-13.955-13.452
-7.881
-5.343
-4.422
-4.709
-2.805
-2.341
-2.132
-1.498
-1.665
-0.257
-1.754
-0.5515.549
-14.511-11.289-10.016
-8.9-5.924
-4.688
-3.824
-3.278
-2.647
-1.88
-1.955
-1.342
-1.302
-1.321-0.988
-0.95-0.264
-13.247-12.981-10.379
-6.329-5.883-4.658
-3.59
-2.491
-2.285
-1.811
-1.569
-1.565
-1.215
-1.242
-1.02
-0.812
-10.017-7.951-7.197
-3.957
-5.78-3.951
-2.907
-2.655
-2.346
-1.744
-1.553
-1.606
-1.246
-1.122
-1.036
-1.032
-0.976
0-4.858-4.206
-3.135
-3.152
-2.794
-2.346
-2.292
-1.983
-1.866
-1.495
-1.122
-1.173
-0.977
-0.894
-0.824
0-3.836-3.794-2.848
-1.704
-1.804
-1.476
-2.067
-1.452
-1.25
-0.856
-0.802
-0.883
-0.909
0-2.17-2.906-2.728
-1.83
-1.419
-1.008
-1.128
-1.072
-0.947
-0.698
-0.644-0.754
-0.587
0-0.982-2.468
-2.152
-1.498
-1.418
-1.002
-1.028
-0.959
-0.946
-0.695
-0.574
-0.65
-0.792-0.732
0
-0.502
-1.148
-1.118
-1.024
-0.919
-0.567
-0.783
-0.709
-0.645-0.626
-0.547
0.006
-0.676
-0.679
-0.834-1.054
-0.447
-0.511
-0.65
-0.453-0.45
0.889
-0.167
-0.488
-0.544-0.645
-0.48
-0.301
-0.194-0.167
-0.0
-10-7.5-5-2.502.557.510
Fig. 21 Brake specific fuel consumption as compared with CR16.5
Vol:.(1234567890)
Research Article SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x
SAAB practiced variable compression ratio technology through its SVC Engine. The technology was implemented by repositioning of the cylinder or cylinder head [24].
FEV is also realized this technology by working on dif-ferent methods. One of them was to use a connecting rod with variable length [27]. While the other one used eccen-tric bearings that change the TDC and BDC positions of the piston [28].
3 Specifications of engine
The study includes numerical modelling of a four-cylinder turbocharged 2.0 L direct injection diesel engine with the specifications shown in Table 1.
4 Model setup
Numerical Modelling was performed using AVL Cruise-MoBEO tool with measurement data of actual engine obtained by dynamometer tests.
A standard AVL engine development testbed with 220 kW dyno and inhouse sensors was used in the collec-tion of different parameters. The sensors were mounted on the test bed upstream and downstream of all the engine components in order to record all the maximum possible pressure, temperature, emissions readings of a running engine on the required test points. The data was collected using AVL PUMA software interface.
Steady-state data collection requires a waiting time for the engine to reach that desired steady state and the read-ings were then recorded for a certain amount of time. Sev-eral readings of the same point were taken, and log-point average of the obtained readings was used.
An intensive data check of the raw data from sensors was performed using post-processing software, AVL Con-certo, in order to make sure that the collected data corre-lated with each other as well as general trends expected to be observed. Out of 300 logged points, only 236 points were filtered to be usable for steady-state characterization of the numerical model.
Figure 3 shows how each log-point of data was col-lected at different rpms and torques. Data was collected
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
5
5
5
55
5
5
027671127349
595181
328
482
089
106
0.55080.65870.86941.10781.5319
1.79462.1883
2.4728
1.9529
5.11846.5922
0.87921.03641.29631.81262.65493.29233.5004
5.3476
7.1652
5.8664
4.928
4.46043.73964.4945
9.28679.2039
1.26141.8252.29992.65873.3384
4.5109
6.3535
4.966
6.5332
4.5747
3.8832
5.9351
3.7355
5.7079
3.1242
3.5027
4.74424.7715
1.91932.84593.2264
5.5383
6.7325
5.3593
4.7901
3.9569
2.6142
3.6367
6.8982
9.8711
2.4712
6.0251
7.17887.1411
2.30172.94183.0543
4.56026.9808
5.9255
5.0391
5.3473
4.4733
1.7154
4.5055
5.8139
3.3123
5.33566.7374
4.78454.4191
3.03244.00334.2969
7.01388.30827.3898
6.8003
5.3123
3.9385
6.0401
4.48
2.7966
6.1933
8.1115
4.2747
5.1621
3.17683.88275.6677
6.0484
6.59386.9348
6.9919
6.0171
6.5551
6.2802
4.3386
4.6043
4.7244
2.4593
3.1039
2.5047
2.2857
3.85134.57245.8845
4.1845
5.0776
5.5856
4.6618
6.2991
5.5592
4.8015
5.0283
4.0334
2.9577
1.7424
1.8615
1.5161
5.25894.9214.4025.5421
5.2717
5.4068
4.3068
5.1744
3.5341
4.6139
3.3112
1.676
3.0123
4.0483
5.5163.66414.98165.3911
5.7848
5.363
5.6228
4.0546
4.0796
3.4697
1.5465
1.22651.1929
0.8896
3.73744.55384.4131
5.8668
4.2013
5.9306
3.8809
3.4445
3.4025
2.3981
2.5568
1.9839
1.1043
0.8121.0648
2.2107
3.3737
2.1199
4.328
3.37
3.5589
2.9561
2.4526
2.5678
1.88740.6517
1.1802
1.7722
4.0535
2.1847
3.11322.8806
1.5279
3.6642
1.1888
0.32940.2036
2.7318
2.4689
1.9265
2.4932.6942
1.6824
1.4154
0.61710.421
0.83
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
61805169927
378144
587
533
695
889
0.22880.25230.30120.39560.6209
0.64750.9529
1.0593
0.8913
2.08772.0231
0.33750.38580.45530.739
0.93231.19891.2972
2.1138
2.1943
2.0779
2.0888
1.60481.29011.7918
2.6432.6062
0.47750.62080.79470.93421.4257
1.4638
2.4476
1.9431
2.585
2.1655
1.4949
2.0988
2.34
2.8844
1.4071
1.1867
2.12722.12
0.66610.97451.1272
1.9794
2.5739
1.9922
2.0994
1.5371
1.2733
1.3205
2.4906
2.0562
0.3203
1.9882
2.12792.0091
0.85040.98231.1448
1.76122.3297
2.2126
1.8153
2.0284
1.9186
1.2731
0.9847
1.5788
0.1471
0.43312.9405
1.80491.8212
1.06421.294
1.4883
2.60183.32812.7639
2.4274
2.2827
1.4685
1.9288
1.7196
1.3975
2.5617
2.1629
1.3873
2.0689
1.09951.30161.614
2.1941
2.432.6488
2.4104
2.3384
2.0544
1.9848
1.555
1.5172
1.4315
1.3194
1.1812
0.9196
0.8507
1.21971.38621.869
1.5792
1.7422
1.9079
1.5356
2.0248
2.0101
1.6716
1.4094
1.5679
1.2361
0.689
0.7019
0.5867
1.83991.63281.54671.8386
1.8699
1.5543
1.5822
1.7332
1.1643
1.2955
1.3436
0.7108
1.0705
1.4536
1.70241.14621.72411.4777
1.6663
1.948
1.8826
1.0309
1.7067
1.306
0.5388
0.4470.428
0.3293
1.03621.3751.0973
2.1796
1.635
1.7525
1.2507
1.267
1.0736
0.7516
0.7093
0.48
0.3363
0.41970.1629
0.6111
0.9828
0.6812
0.6686
1.0498
0.9608
0.8473
0.7909
0.8291
0.45950.067
0.2894
0.4859
1.4979
0.6911
1.1790.7769
0.5627
1.0879
0.5499
0.30070.0708
0.6234
0.6767
0.5822
0.70480.7613
0.6303
0.422
0.14350.1814
0.22
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
596811127537
086358
257
081
163
066
-0.1823-0.2529-0.2916-0.3375-0.4598
-0.716-0.7828
-1.1371
-0.7757
-1.5151-2.0603
-0.3427-0.3743-0.3954-0.5468-0.9475-1.0955-1.2892
-1.6469
-1.7504
-1.5401
-2.092
-1.3441-1.2915-1.5015
-1.6501-1.7001
-0.465-0.5467-0.6578-0.773-1.0512
-1.3134
-2.2933
-2.0233
-2.0373
-2.3729
-1.4179
-1.6738
-2.4587
-3.3357
-1.7123
-1.4285
-1.3747-1.8255
-0.589-0.782-0.9303
-1.7473
-1.9867
-2.3772
-1.8761
-1.438
-1.4115
-0.5601
-1.5426
-0.8556
-3.5291
0.3083
0.24770.2419
-0.799-0.8361-0.955
-1.778-1.8134
-2.5147
-1.6527
-1.8178
-1.6526
-1.3622
-0.1653
-1.8021
-0.3761
-1.3506-4.6373
-2.0529-3.8926
-0.6003-0.9984-1.1679
-2.0851-2.4627-2.3681
-2.1019
-2.147
-1.2791
-1.3675
-1.9687
-2.4625
-1.2887
-0.9999
-1.4639
-2.2893
-0.8237-1.0243-1.1983
-1.8577
-2.1646-1.8517
-1.809
-2.0957
-2.0955
-1.6224
-2.0694
-1.4258
-1.2242
-1.903
-0.4292
-1.0878
-0.8556
-0.8265-1.0643-1.4904
-1.5071
-1.3682
-1.5499
-1.1457
-1.6312
-1.6301
-1.3755
-1.175
-1.523
-0.9913
-0.7059
-0.5644
-0.6488
-1.4374-1.3088-1.2087-1.3568
-1.6471
-1.1474
-1.5391
-1.3633
-0.9618
-1.0918
-1.2207
-0.6354
-0.8795
-1.0759
-1.2624-1.0864-1.2803-0.9663
-1.2044
-1.5321
-1.5084
-0.7918
-1.2573
-0.4652
-0.4503
-0.3658-0.3726
-0.3095
-0.7169-0.9722-0.9542
-1.4766
-1.41
-1.3743
-0.9512
-0.8885
-0.7064
-0.5977
-0.5601
-0.3669
-0.2559
-0.2784-0.1403
-0.4502
-0.732
-0.5436
-0.5722
-0.7854
-0.7556
-0.6396
-0.6045
-0.619
-0.3249-0.3505
-0.2199
-0.3688
-1.0721
-0.628
-1.0225-0.626
-0.4463
-0.7621
-0.4064
-0.2318-0.0731
-0.3973
-0.5232
-0.5224
-0.5979-0.6149
-0.4645
-0.31
-0.0534-0.1373
-0.15
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-5 -5
-5
-5
-5
307473247
565
519326
026
369
434
157
-0.4007-0.5042-0.5995-0.7511-1.021
-1.6001-1.8377
-2.4677
-2.0695
-2.7185-4.2021
-0.7094-0.7785-0.9031-1.225
-1.8434-2.4027-2.7603
-3.7481
-4.2599
-3.545
-4.8465
-3.27-3.0757-3.0762
-3.7771-3.8294
-0.9435-1.1591-1.4634-1.7407-2.2495
-3.0596
-4.5895
-4.6367
-4.0346
-4.9147
-2.9931
-3.422
-4.5757
-4.4277
-3.8559
-3.2722
-2.701-3.2211
-1.2578-1.6538-1.9879
-3.6304
-4.2144
-5.637
-4.1166
-3.3175
-3.1585
-1.7602
-3.1753
-1.5118
-9.5738
-0.2321
-5.1049
-9.5694
-1.5718-1.8705-2.0705
-3.3817-3.4868
-5.2109
-3.8119
-4.021
-3.7355
-3.3608
-0.7185
-4.5584
-1.9891
-2.8896-4.823
-5.8245-8.0498
-1.3586-2.0932-2.4564
-4.5218-4.7823-5.0343
-4.4263
-4.2738
-2.5784
-2.9937
-4.3171
-5.0756
-1.268
-0.9799
-5.6412
-5.6341
-1.6361-2.1454-2.5532
-3.9297
-4.4028-4.0011
-4.1008
-4.3647
-4.5541
-3.5219
-4.392
-2.8113
-2.8824
-3.4839
-1.1613
-1.9487
-1.9694
-1.6163-2.1602-2.8027
-3.4462
-2.7399
-2.8445
-2.5208
-3.3823
-3.9408
-2.9378
-2.6076
-3.2442
-2.1877
-1.5812
-1.2136
-1.467
-2.8176-2.8304-2.6231-2.9419
-3.5293
-2.4678
-3.9564
-2.7247
-2.1072
-2.2774
-2.5527
-1.5613
-1.9447
-1.9115
-2.6047-2.3606-2.8185-2.1115
-2.4379
-3.204
-3.1765
-1.7056
-2.3825
-1.0048
-0.9882
-0.6661-0.8435
-0.6855
-1.5231-2.1458-2.1095
-3.0371
-3.072
-2.9177
-2.0907
-1.9295
-1.5175
-1.3128
-1.2137
-0.7423
-0.5886
-0.5945-0.5062
-1.0983
-1.8493
-4.9947
-1.3286
-1.8299
-1.7644
-1.3523
-1.3886
-1.322
-0.7255-0.74
-0.1652
-0.9183
-2.4827
-1.5388
-2.5108-1.5177
-1.0183
-1.3927
-0.834
-0.4928-0.0399
-0.8975
-1.3245
-1.3495
-1.4374-1.3713
-0.9966
-0.6598
-0.1338-0.3115
-0.35
-10-7.5-5-2.502.557.510
Fig. 22 Mass flow of intake air as compared with CR16.5
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SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x Research Article
from the engine starting from 900 rpm all the way till 4500 rpm making steps uptil maximum achievable torque at each rpm step. Figure 3 shows the numbering of log-points in the sequence tests were conducted. A total of 236 log-points covering all the scenarios of rpms and torques were recorded starting from low torque for each rpm, going up to the maximum torque achievable for that rpm. Figure 3 indicates that log-points number 90, 107 and 125 have recorded the maximum torque of approximately 405 Nm @ 2000, 2250 and 2500 rpms respectively.
4.1 Standalone model simulation
The basic purpose of standalone model is to study the working of semi-physical characterized in-cylinder para-metrization before moving on the full physical airpath. The in-cylinder combustion refinement is performed at this stage to check if the semi-physical model works in correlation with the physical engine. Standalone model as shown in Fig. 4, includes MoBEO cylinder, intake and exhaust manifolds and system boundaries.
Standalone model approach is used to check if MoBEO model configuration fits the combustion parameters of the engine.
4.2 Full model characterization and simulation
In Fig. 5, a full model of a 2.0 L, 4-cylinder turbocharged diesel engine can be seen. The engine has one single stage turbo charger with variable geometry turbine (VGT), sin-gle-step high pressure exhaust gas recirculation (EGR), die-sel particle filter (DPF), selective catalytic reduction (SCR), lean NOx trap (LNT) and muffler.
After the creation of general engine model, sizing of components including their volumes, dimensions, heat transfer coefficients and other parameters are set to con-cede with the physical components. The model consists of plenums, restrictions, solid walls, turbo components, heat transfers and other components like functions and constant table blocks. PID controllers are used to char-acterize the required components.
After the whole model is characterized, a full open-loop (without PID control) simulation is given to see the proximity of the model with the actual measurement data. Some tunings/refinements are also performed after this stage to eliminate minor characterization errors. The obtained 236 steady-state log points at different load conditions were validated at steady-state and transient
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900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
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949078004112
358344
589
535
382
136
0-23.176-22.971-20.687-19.1
-11.646-9.055
-8.028
-6.842
-4.996-3.588
-25.58-22.344-19.031-17.085-15.655-13.619-8.89
-6.123
-5.179
-3.744
-3.525
-2.902-3.037-2.865
-1.747-1.789
0-23.058-20.253-17.54-13.464
-11.229
-7.892
-7.271
-5.392
-4.395
-3.186
-2.58
-2.644
-2.361
-2.618
-2.118
-1.604-1.524
-18.055-20.062-17.688
-9.322
-7.169
-6.522
-4.939
-3.593
-2.831
-2.263
-1.387
-1.364
-2.037
-1.679
-0.96-0.845
-18.488-16.411-13.071
-10.753-7.69
-6.582
-4.899
-3.911
-3.053
-2.344
-2
-1.733
-1.781
-1.601-1.946
-1.798-1.622
-9.08-19.711-15.274
-9.694-8.059-6.94
-5.077
-3.325
-3.061
-2.495
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-3.565
-3.025
-2.83
-2.606
-2.513
-1.856
-1.768
-1.75
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0-9.475-7.935
-6.677
-5.655
-4.378
-4.132
-4.159
-3.714
-3.502
-2.741
-2.109
-1.967
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-1.47
-1.337
0-8.606-7.732-5.585
-3.351
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-1.573
-1.445
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0-6.523-6.767-6.061
-3.516
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-2.365
-2.254
-1.625
-1.364
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-0.916
0-4.53-5.219
-4.794
-3.145
-2.989
-2.422
-2.346
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-2.092
-1.509
-1.311
-1.494
-1.833-1.669
0
-2.911
-2.342
-2.366
-2.373
-1.842
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-1.891-1.73
-1.603
-1.522
-1.886
-1.473
-1.5-2.792
-1.249
-1.929
-1.789
-1.479-1.184
-1.08
-1.303
-1.176
-1.32-2.429
-1.496
-1.25
-0.896-0.818
-0.8
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983.27956228
335031
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223
254
551
0-10.711-10.318-9.025-8.468
-5.006-3.817
-3.6
-2.502
-1.913-2.043
-11.961-10.222-8.31-7.258-6.531-5.803-3.715
-2.589
-2.278
-1.588
-1.44
-1.244-1.287-1.183
-0.879-0.904
0-9.998-8.567-7.439-5.516
-4.641
-3.227
-2.949
-2.16
-1.765
-1.282
-1.044
-0.942
-0.816
-1.014
-0.885
-0.543-0.557
-7.229-8.328-7.352
-3.769
-2.799
-2.373
-2.294
-1.387
-1.135
-0.921
-0.562
-0.612
-0.937
-0.644
-0.422-0.404
-7.626-6.627-5.307
-4.575-2.909
-2.497
-1.963
-1.553
-1.222
-0.906
-0.846
-0.73
-0.671
-0.7-0.63
-0.731-0.602
-8.188-7.718-5.951
-3.571-3.182-2.592
-1.95
-1.327
-1.14
-0.905
-0.895
-0.836
-0.671
-0.637
-0.689
-0.593
-5.294-5.104-4.415
-2.864
-2.735-2.244
-1.662
-1.523
-1.31
-1.029
-0.985
-0.942
-0.834
-0.684
-0.613
-0.623
-0.555
0-3.278-2.71
-2.189
-1.948
-1.609
-1.409
-1.399
-1.244
-1.165
-0.949
-0.711
-0.711
-0.589
-0.519
-0.48
0-2.71-2.5
-1.855
-1.113
-1.053
-0.986
-1.336
-0.938
-0.803
-0.522
-0.501
-0.529
-0.551
0-1.811-2.036-1.893
-1.128
-0.845
-0.9
-0.749
-0.707
-0.562
-0.43
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-0.317
0-1.059-1.431
-1.458
-0.948
-0.919
-0.707
-0.706
-0.677
-0.649
-0.455
-0.344
-0.436
-0.551-0.503
0
-0.571
-0.577
-0.663
-0.657
-0.512
-0.52
-0.574
-0.511
-0.506-0.48
-0.436
-0.124
-0.422
-0.332
-0.411-0.696
-0.32
-0.46
-0.562
-0.393-0.344
0.155
-0.111
-0.21
-0.28-0.535
-0.435
-0.288
-0.198-0.166
-0.1
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6 6 68 8 8
10 10815653536342
319222
85
785
673
76
014.22812.4189.8168.54
5.1663.971
3.829
2.413
2.3482.313
14.24611.5018.8217.1246.3425.5754.022
2.658
2.33
1.684
1.351
1.2541.2521.209
1.0861.062
010.5388.6577.5155.42
4.437
3.213
2.428
2.113
1.547
1.213
1.046
0.786
0.562
0.88
0.761
0.6470.512
7.1568.1277.202
3.682
2.507
2.069
2.152
1.277
1.046
0.978
0.64
0.711
0.318
0.83
0.840.824
7.3165.6864.923
4.252.693
2.188
1.766
1.45
1.163
0.845
0.884
0.634
0.616
0.5930.2
0.5510.151
5.0356.7385.274
3.0772.8452.234
1.696
1.178
1.012
0.832
0.728
0.707
0.539
0.538
0.553
0.433
4.4754.0223.631
2.356
2.8481.908
1.391
1.271
1.078
0.844
0.758
0.758
0.613
0.539
0.492
0.492
0.457
02.5022.077
1.506
1.51
1.317
1.124
1.103
0.977
0.907
0.729
0.545
0.57
0.465
0.427
0.384
01.9061.8781.379
0.838
0.844
0.734
1.009
0.711
0.604
0.415
0.388
0.421
0.431
01.0961.4181.337
0.862
0.665
0.49
0.551
0.52
0.468
0.333
0.3060.338
0.269
00.4931.179
1.029
0.722
0.672
0.49
0.503
0.472
0.468
0.336
0.269
0.314
0.3880.358
0
0.189
0.407
0.479
0.462
0.344
0.323
0.382
0.352
0.3260.315
0.28
-0.058
0.252
0.252
0.3270.461
0.204
0.264
0.345
0.2360.223
-0.466
-0.009
0.148
0.1930.291
0.258
0.148
0.0940.078
0.0
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6
8
10
10
25980947946
549588
635
306
226
323
23.25936.66834.88924.46820.191
12.429.552
9.088
5.647
6.2345.983
39.02229.81522.47316.98314.48413.07910.086
6.017
5.422
3.922
2.987
2.8372.8582.867
2.4922.463
10.87226.12920.69418.01212.688
10.023
7.501
5.417
5.508
3.586
2.89
2.448
1.925
1.856
1.958
1.703
1.5921.4
16.83816.21815.543
8.555
5.644
4.627
4.941
2.886
2.397
2.178
1.521
1.693
0.258
1.786
0.553-13.457
16.97412.72611.131
9.7696.297
4.918
3.976
3.389
2.719
1.916
1.994
1.361
1.319
1.3390.998
0.9590.265
15.2714.91711.581
6.7566.2514.886
3.724
2.555
2.338
1.845
1.594
1.59
1.23
1.258
1.031
0.819
11.1328.6377.756
4.12
6.1354.113
2.994
2.727
2.402
1.775
1.577
1.632
1.262
1.135
1.046
1.042
0.985
05.1064.391
3.237
3.255
2.874
2.403
2.346
2.023
1.902
1.517
1.135
1.187
0.986
0.902
0.83
03.9893.9432.932
1.734
1.837
1.498
2.111
1.474
1.266
0.863
0.808
0.89
0.917
02.2182.9932.805
1.864
1.44
1.018
1.141
1.083
0.956
0.703
0.6480.76
0.591
00.9922.53
2.2
1.52
1.439
1.013
1.039
0.968
0.955
0.7
0.578
0.655
0.7980.737
0
0.505
1.161
1.13
1.034
0.927
0.57
0.789
0.714
0.6490.63
0.55
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0.68
0.684
0.8411.065
0.449
0.514
0.654
0.4550.452
-0.882
0.168
0.49
0.5470.649
0.482
0.302
0.1940.167
0.0
-10-7.5-5-2.502.557.510
Fig. 23 Thermal efficiency as compared with CR16.5
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Research Article SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x
conditions to make sure they pass the quality gates of the characterized parameters of the engine model.
4.3 VCR simulation setup
The numerical model inputs tab allowed the compres-sion ratio to be connected as a parameter of input and thus change it according to the case to be studied. After the full model was setup and characterized, studies of VCR were conducted by altering this factor as shown in Fig. 6.
5 Results and discussion
5.1 Results from steady state simulation
The steady-state results are shown as below. The map shows the difference between the simulation and meas-urement data (measurement-simulation) where the green colour dominates the model to be working accurately:
z-axis = Measurement Result − Simulation Result
As can be seen in Figs. 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 and 18, the difference between the results obtained from steady-state simulations of the model and the measure-ment data is negligible for most of the regions of the maps. This indicates that the characterised numerical model is working very similar to the actual engine.
VCR Simulation study was conducted after the valida-tion of the correct working of the open loop numerical model of the engine.
5.2 Results from numerical model with VCR
5.2.1 Strategy of VCR implementation in numerical model
All the maps of the engine are given in terms of rpm on x-axis, torque on y-axis and percentage change on z-axis. The main strategy applied to the model was to keep the torque and rpm constant with the operational map of CR16.5. At different compression ratios, torque was expected to increase or decrease for the same fuel quan-tity, thus a shift in the whole map can occur and could make the comparison of the graphs complicated and
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439096939.71
2.4015
653
066
881
982
16.253-9.266-10.116
-19.348-29.003
-14.478-2.492
-0.879
0.097
2.57.15
19.58710.2031.485-3.985-6.778-4.884-4.884
-0.733
0.965
0.904
1.678
2.5992.7394.658
16.05315.762
26.30912.9987.6029.6814.975
0.595
-0.502
-1.347
-0.126
-0.424
0.957
2.951
1.913
3.614
2.133
2.87
6.0426.853
19.91917.29218.594
3.079
0.23
-0.611
-0.408
-0.497
-0.516
1.241
3.33
4.347
0.954
5.34
10.41211.76
29.29522.56117.618
9.9143.682
2.161
0.564
0.753
0.603
0.853
0.393
1.399
0.852
3.0324.145
3.7513.752
38.74131.51122.178
8.894.8593.499
1.287
0.755
0.824
0.341
0.493
0.4
2.472
5.025
2.087
3.676
26.17323.83717.148
9.395
5.9424.083
1.722
1.424
1.216
0.837
0.733
1.186
1.608
0.739
2.038
1.811
1.601
21.63918.08313.423
11.445
6.114
3.477
2.971
2.119
1.499
1.317
1.031
0.852
0.818
0.861
1.832
1.104
19.53917.96615.1176.774
3.222
2.092
2.403
2.149
1.515
0.87
0.518
0.031
2.863
3.937
19.10118.94614.7489.247
4.061
2.058
2.274
1.038
0.941
0.957
0.692
0.7421.483
1.379
18.22716.40614.253
8.028
5.919
2.564
1.814
1.472
0.96
1.171
0.287
0.542
0.912
1.0181.044
12.162
7.75
5.325
2.419
1.842
0.232
-0.069
0.225
-0.364
-0.432-0.405
-0.39
6.106
-0.042
1.07
-0.7691.129
-0.777
-2.532
-1.859
-1.995-2.463
5.712
2.981
1.28
-1.387-0.971
-1.988
-2.566
-2.938-3.403
-3.7
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52267866834
925296
446
239
109
483
10.19-1.368-1.611-5.509-9.756
-5.499-0.44
-0.12
0.316
1.4451.136
9.9245.8691.991-0.353-1.74-1.307-1.691
-0.181
0.213
0.493
0.925
0.930.861.95
4.884.727
12.1646.54
4.0974.5982.344
0.531
-0.036
-0.392
0.091
0.161
0.483
1.201
2.149
1.976
1.114
0.806
3.0363.08
7.9557.2577.604
1.364
0.163
-0.223
0.105
-0.118
0.105
0.529
1.506
1.303
-0.429
1.86
3.2313.378
11.2668.7326.976
4.2071.505
0.819
0.232
0.373
0.304
0.243
0.277
0.493
-0.333
0.0142.085
1.3461.616
14.13711.3878.28
3.1871.7631.211
0.482
0.241
0.36
0.224
0.289
0.348
1.279
1.333
0.705
1.542
9.4058.486.627
3.273
1.9621.492
0.588
0.421
0.507
0.301
0.28
0.404
0.454
0.63
0.825
0.635
0.531
7.8436.6554.984
3.791
2.184
1.307
1.02
0.729
0.465
0.429
0.281
0.393
0.431
0.412
0.66
0.384
5.5226.0965.0372.404
1.032
0.903
0.645
0.754
0.505
0.283
0.28
0.09
0.993
1.336
6.126.2484.7493.398
1.51
0.561
0.639
0.378
0.365
0.386
0.266
0.2860.517
0.465
5.9995.4675.014
2.343
1.659
0.946
0.543
0.413
0.332
0.459
0.159
0.228
0.358
0.530.289
3.943
2.467
1.645
1.479
0.558
0.143
-0.014
0.068
-0.089
-0.086-0.005
-0.039
1.849
-0.455
0.236
-0.520.321
-0.309
-0.796
-0.684
-0.589-0.79
1.845
0.882
0.294
-0.477-0.497
-0.791
-0.868
-0.967-1.105
-1.2
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
0
00
0
0
0
136407032388
00917
249
46
093
372
-12.773-2.449-1.7982.2856.237
4.118-0.133
-0.569
-0.535
-0.107-1.251
-11.662-7.587-3.618-1.0660.2940.2320.935
0.171
-0.359
-0.445
-1.266
-0.836-0.991-1.549
-2.112-2.267
-13.093-7.512-4.976-5.115-2.807
-0.952
-0.331
0.238
-0.077
-0.802
-0.628
-1.03
-2.863
-2.856
-1.624
-1.628
-1.612-2.949
-7.652-7.033-7.183
-1.558
-0.242
-0.229
-0.266
-0.14
-0.502
0.113
-1.071
-0.588
-3.077
1.052
2.2192.406
-9.804-7.202-6.272
-3.734-1.577
-0.421
-0.346
-0.463
-0.391
-0.294
-0.358
-0.785
0.01
-0.863-4.701
-1.853-6.14
-5.432-9.144-7.022
-2.776-1.743-0.987
-0.414
-0.238
-0.414
-0.278
-0.511
-1.155
-0.693
-0.552
-0.82
-1.951
-7.742-6.62-5.472
-2.629
-1.964-1.379
-0.554
-0.274
-0.319
-0.292
-0.401
-0.462
-0.456
-1.287
-0.205
-0.718
-0.487
-6.428-5.349-4.02
-2.558
-1.741
-1.04
-0.845
-0.544
-0.355
-0.343
-0.276
-0.483
-0.364
-0.461
-0.503
-0.531
-4.407-4.604-3.885-1.913
-0.645
-0.763
-0.309
-0.548
-0.388
-0.271
-0.286
-0.143
-0.696
-0.847
-4.526-4.375-3.569-2.664
-1.187
-0.392
-0.246
-0.293
-0.296
-0.195
-0.233
-0.237-0.378
-0.313
-4.406-4.091-3.863
-1.914
-1.071
-0.624
-0.364
-0.311
-0.274
-0.373
-0.16
-0.204
-0.286
-0.394-0.25
-2.904
-1.698
-1.228
-1.047
-0.406
-0.083
0.018
-0.061
0.019
-0.005-0.089
-0.057
-1.341
0.273
-0.102
0.502-0.183
0.203
0.545
0.444
0.3750.537
-1.116
-0.608
-0.137
0.4080.494
0.649
0.615
0.6590.77
0.9
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-20
-10
-10
0 0
00
0
0
10
0
887.2781433
76914
489
343
09
023
-34.102-10.963-9.61.025
10.023
7.574-1.387
-2.136
-1.651
1.342-1.218
-29.358-19.84-10.789-4.324-0.824-0.821.262
-0.128
-1.406
-1.49
-3.439
-2.501-2.668-2.908
-5.083-5.226
-31.351-18.647-12.583-12.562-7.15
-2.717
-1.104
0.004
-0.229
-1.874
-1.55
-2.235
-5.25
-3.819
-3.917
-3.999
-2.595-4.231
-17.479-14.246-15.247
-3.989
-0.852
-0.933
-0.839
-0.689
-1.374
-0.587
-2.379
-1.155
-10.305
1.052
-10.024-35.265
-21.485-15.585-13.809
-8.839-4.102
-1.116
-0.962
-1.23
-1.125
-0.737
-1.027
-2.373
-1.058
-1.97-4.503
-6.414-14.136
-20.35-19.245-14.954
-6.016-4.092-2.192
-1.045
-0.65
-1.153
-0.778
-1.36
-2.586
-0.471
-0.121
-3.793
-5.438
-16.28-14.001-11.53
-4.632
-4.356-2.892
-1.11
-0.658
-0.793
-0.715
-0.989
-0.951
-1.293
-2.398
-0.695
-1.21
-1.043
-13.259-11.177-8.847
-5.179
-3.815
-2.534
-1.744
-1.165
-0.666
-0.759
-0.683
-1.123
-0.894
-1.049
-1.021
-1.083
-9.428-9.502-7.913-3.922
-1.227
-1.581
-0.233
-1.149
-0.809
-0.609
-0.651
-0.469
-1.349
-1.307
-9.327-8.871-7.139-5.343
-2.491
-0.784
-0.43
-0.607
-0.617
-0.449
-0.497
-0.483-0.736
-0.569
-9.086-8.221-7.727
-3.897
-1.929
-1.173
-0.653
-0.591
-0.568
-0.748
-0.362
-0.448
-0.572
-0.767-0.596
-5.939
-3.235
2.326
-2.125
-0.724
-0.277
0.085
-0.082
0.004
-0.075-0.245
-0.075
-2.775
0.704
-0.145
1.351-0.334
0.396
0.897
0.791
0.6541.093
-2.326
-1.182
-0.186
0.820.956
1.299
1.141
1.1961.432
1.7
-10-7.5-5-2.502.557.510
Fig. 24 Engine out NOx as compared with CR16.5
Vol.:(0123456789)
SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x Research Article
more difficult. Therefore, the same set-point torque was achieved by connecting a PID to control the fuel quantity.
For different compression ratios, as the fuel quantity changes to achieve the same operational conditions, mass-flow of intake air also changes, while EGR valve posi-tion remains the same causing the Intake Air:EGR ratio to change for the particular set-point. To study changes in NOx more accurately, the percentage of mass flow of EGR at each log point was kept the same with the original data of CR16.5 through the following formula:
The graph of the percentage of EGR in the total mass flow taken from CR16.5 is shown in Fig. 19.
The results are calculated as percentages of increase or decrease as compared to CR16.5:
(4)MFEGR =MFEGR
MFIA +MFEGR× 100%
(5)Result =NewCR − CR16.5
CR16.5
5.2.2 Mass flow of fuel
As explained earlier, the torque was kept constant at every set-point by changing the fuel quantity using a PID.
As the compression ratio increases, the torque pro-duced for the same fuel quantity also increased, thus PID decreased the torque to the original point by decreasing the fuel quantity.
The opposite can be seen when the compression ratio was decreased, which was due to more fuel was required to produce the same set-point torque. Figure 20 illus-trates a decrease in fuel quantity as compression ratio is increased and an increase in fuel quantity as compression ratio is decreased.
5.2.3 Brake specific fuel consumption
The figures shown in Fig. 21, shows the percentage change in the brake specific fuel consumption values at different compression ratios as compared with compression ratio 16.5. It can be clearly observed that the BSFC increases as compression ratio decreases and decreases as the com-pression ratio increases.
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-2
-2
0
0
0
0
0
0
0
00
0
2 2 4
4
6833571
968
32841
831
343
286
42
-10.7960.7140.9851.3790.709
2.1281.681
0.443
0.491
-0.605-0.337
2.0342.1022.5630.553-1.692-2.1840.907
0.868
0.131
0.305
0.133
0.3380.15
-0.095
-0.104-0.11
3.3731.9261.2951.1850.953
-0.008
0.864
-0.397
-0.227
0.037
0.717
0.436
0.293
0.012
-0.24
-0.093
0.0060.026
11.750.2080.251
0.545
0.541
-0.462
-0.165
0.316
0.37
0.261
0.302
0.217
0.027
0.037
0.0750.075
14.766.8685.067
-0.6751.555
0.539
0.203
-0.034
0.061
0.306
0.192
0.176
0.353
0.140.128
0.0640.099
5.3422.6471.789
0.265-0.173-0.025
0.24
0.336
0.277
0.295
0.191
0.207
0.419
0.203
0.2
0.162
4.2211.9491.33
-0.03
-0.3260.466
0.584
0.152
0.132
0.296
0.288
0.136
0.204
0.208
0.253
0.196
0.185
6.2013.9112.929
1.139
0.681
1.004
0.806
0.23
0.034
-0.054
0.191
0.495
0.283
0.268
0.289
0.218
2.137-0.87-0.813-0.088
0.799
0.671
0.832
-0.199
0.295
0.193
0.629
0.457
0.312
0.193
1.6440.975-1.415-1.259
0.539
1.088
0.54
0.337
0.156
0.348
0.448
0.350.208
0.346
2.951.624-0.439
-0.621
0.486
0.214
0.778
0.411
0.204
0.307
0.354
0.389
0.436
0.20.301
1.887
0.083
0.305
0.07
0.062
0.536
0.519
0.173
0.35
0.3210.304
0.487
0.801
0.347
0.361
0.166-0.966
0.549
0.423
0.421
0.3930.309
0.812
0.465
0.414
0.133-0.642
0.483
0.367
0.3830.384
0.3
-4
-2.5
-1
0.5
2
3.5
5
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
0
0
0
0
0
0
0
0
24 695315672405
611052
68
086
257
303
-4.617-0.0050.390.535-0.128
0.850.729
0.095
0.602
-0.039-0.247
0.790.5760.9920.227-0.563-0.8750.366
0.36
0.05
0.125
0.059
0.1420.102-0.032
-0.062-0.064
1.3790.8520.5350.4460.427
0.013
0.287
-0.143
-0.078
0.028
0.29
0.179
0.132
0.047
-0.083
-0.037
0.0130.012
4.7710.150.157
0.225
0.218
0.067
-0.424
0.192
0.157
0.113
0.128
0.09
0.005
0.026
0.030.031
5.0592.4791.904
-0.6160.577
0.219
0.1
0.002
0.038
0.132
0.085
0.081
0.164
0.0640.071
0.0350.052
2.0081.120.713
0.147-0.1710.039
0.115
0.151
0.127
0.131
0.098
0.094
0.18
0.103
0.099
0.081
1.5730.870.562
0.06
-0.158-0.01
0.234
0.084
0.08
0.136
0.138
0.05
0.122
0.107
0.122
0.099
0.092
2.1541.4041.055
0.521
0.268
0.266
0.307
0.116
0.054
0.026
0.108
0.206
0.11
0.132
0.136
0.105
2.112-0.082-0.1970.027
0.305
0.266
0.358
-0.12
0.144
0.092
0.247
0.199
0.145
0.101
0.9820.497-0.289-0.279
0.221
0.328
0.271
0.166
0.096
0.139
0.204
0.160.113
0.156
1.0940.67
0.044
-0.163
0.196
0.116
0.283
0.177
0.121
0.135
0.16
0.167
0.185
0.1030.132
0.715
0.207
0.178
0.103
0.089
0.217
0.211
0.106
0.156
0.1710.141
0.19
0.347
0.189
0.202
0.118-0.155
0.215
0.174
0.178
0.1620.136
0.387
0.258
0.209
0.132-0.051
0.195
0.16
0.1610.156
0.1
-4
-2.5
-1
0.5
2
3.5
5
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-2
0 0
0
000
0
0 0
0
0
0
63376679
551
37972
805
257
336
954
-0.5852.3060.588-0.291-0.067
-0.689-0.697
0.055
-0.749
0.0540.441
-0.646-0.507-0.881-0.5310.31
0.5510.011
-0.354
-0.046
-0.126
-0.061
-0.134-0.1020.031
0.0870.084
-0.961-0.813-0.523-0.407-0.395
-0.034
-0.092
-0.236
0.07
-0.057
-0.276
-0.181
-0.124
-0.049
0.058
0.027
-0.007-0.017
-3.86-0.215-0.21
-0.051
-0.289
-0.071
0.369
-0.186
-0.157
-0.116
-0.136
-0.094
-0.073
-0.01
-0.009-0.017
-3.975-2.655-1.631
0.428-0.406
-0.208
-0.108
-0.017
-0.05
-0.134
-0.091
-0.092
-0.172
-0.091-0.089
-0.054-0.065
-1.524-1.225-0.674
-0.1820.119-0.063
-0.126
-0.154
-0.135
-0.142
-0.113
-0.001
-0.178
-0.112
-0.113
-0.091
-1.392-1.125-0.557
-0.192
0.742-0.032
-0.226
-0.105
-0.103
-0.148
-0.152
-0.083
-0.189
-0.128
-0.137
-0.115
-0.107
-1.764-1.186-0.9
-0.727
-0.324
-0.223
-0.283
-0.134
-0.09
-0.07
-0.134
-0.205
-0.137
-0.162
-0.153
-0.117
-1.641-0.1490.067-0.153
-0.346
-0.254
-0.311
0.035
-0.162
-0.122
-0.244
-0.205
-0.151
-0.123
-1.013-0.5590.0570.067
-0.22
-0.262
-0.422
-0.18
-0.126
-0.169
-0.21
-0.173-0.135
-0.17
-1.032-0.6810.159
0.008
-0.197
-0.137
-0.256
-0.186
-0.157
-0.147
-0.171
-0.179
-0.193
-0.132-0.15
-0.713
-0.388
-0.206
-0.142
-0.13
-0.214
-0.22
-0.137
-0.156
-0.175-0.153
-0.185
-0.355
-0.215
-0.214
-0.140.031
-0.209
-0.178
-0.17
-0.166-0.142
-0.593
-0.281
-0.223
-0.158-0.058
-0.192
-0.165
-0.164-0.156
-0.1
-4
-2.5
-1
0.5
2
3.5
5
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-4
-20 0
0
0
0
0
216392786382
295237
174
77
051
58
-0.9975.1253.51-0.624-0.543
-1.49-1.537
-0.013
-1.693
0.1731.018
-1.079-1.079-1.381-1.3540.0931.04
0.482
-0.981
-0.11
-0.258
-0.204
-0.308-0.2360.006
0.1920.188
-2.117-1.871-1.301-0.901-0.882
-0.27
-0.22
-0.564
0.632
-0.139
-0.539
-0.423
-0.292
-0.112
0.116
0.048
-0.011-0.035
-8.105-3.224-1.842
-0.027
-0.679
-0.168
0.811
-0.431
-0.369
-0.267
-0.324
-0.233
-0.19
-0.055
-0.1-0.805
-8.302-5.71-3.577
0.855-0.692
-0.476
-0.261
0.002
-0.06
-0.317
-0.223
-0.226
-0.413
-0.23-0.198
-0.15-0.159
-3.804-2.694-1.542
-0.4580.172-0.172
-0.304
-0.485
-0.274
-0.359
-0.28
-0.036
-0.428
-0.277
-0.279
-0.221
-3.28-2.508-1.304
-1.674
1.484-0.109
-0.516
-0.265
-0.159
-0.395
-0.377
-0.235
-0.455
-0.323
-0.344
-0.288
-0.271
-4.193-2.778-2.025
-1.622
-0.777
-0.529
-0.647
-0.336
-0.243
-0.207
-0.343
-0.489
-0.35
-0.401
-0.38
-0.293
-3.554-0.5120.005-0.415
-0.924
-0.591
-0.683
0.004
-0.402
-0.319
-0.571
-0.49
-0.379
-0.32
-2.355-1.373-0.0130.029
-0.522
-0.608
-0.93
-0.44
-0.33
-0.418
-0.504
-0.426-0.321
-0.42
-2.548-1.6360.242
-0.078
-0.52
-0.341
-0.591
-0.45
-0.392
-0.37
-0.414
-0.433
-0.47
-0.342-0.372
-1.756
-0.929
-0.379
-0.35
-0.326
-0.317
-0.607
-0.343
-0.382
-0.418-0.375
-0.445
-0.893
-0.499
-0.503
-0.3180.056
-0.495
-0.419
-0.398
-0.397-0.352
-1.468
-0.645
-0.518
-0.352-0.153
-0.447
-0.387
-0.387-0.368
-0.3
-4
-2.5
-1
0.5
2
3.5
5
Fig. 25 Mechanical efficiency as compared with CR16.5
Vol:.(1234567890)
Research Article SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x
The effect of this change is seen to be more at low load-low rpm conditions and this trend decreases at high load-high rpm conditions.
5.2.4 Mass flow of intake air
As shown in Fig. 20, a decrease in compression ratio com-pels an increase in mass flow of fuel to achieve the same set-point torque. Since the mass flow of fuel is increased, this also increases the mass flow of intake air as seen in Fig. 22, when the compression ratio decreases. Vice versa phenomenon is observed when compression ratio is increased.
5.2.5 Thermal efficiency
The figures shown in Fig. 23 shows the percentage change in the thermal efficiency values at different compression ratios as compared with compression ratio 16.5. Thermal efficiency is:
(6)�t =Wc
mfQHV
=Ps
�f QHV
where Wc is work per cycle, Ps is power output, mf is mass of fuel per cycle, QHV is heating value of fuel and µf is Fuel mass flow rate.
QHV for diesel is 43.5 MJ/kg so Eq. (6) can be written as:
Matching the inverse proportionality of the formula shown above and trend shown in BSFC values in Fig. 23, it can be clearly observed that the thermal efficiency increases as compression ratio increases and decreases as the compression ratio decreases.
This change is seen to be more prominent at low load-low rpm conditions and becomes less prominent towards high load-high rpm conditions.
5.2.6 NOx
Figure 24 shows that with an increase in compression ratio there is a decrease in NOx and vice versa.
This phenomenon is based on the fact that a higher compression ratio means a more complete combustion and combining it with the observation from Fig. 20, less
(7)�t =1
Sfc ⋅ QHV
=3600
Sfc (g∕kWh)QHV (MJ∕kg)=
82.76
Sfc
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-5
0 00
0 0
0
0
0
0
5
296854159378
165929
992
97
65
714
46.23928.74628.19524.26521.26
10.8887.372
5.868
5.053
0.341-2.016
32.79527.20821.77418.29615.25111.8535.865
1.08
-1.532
-1.762
-1.135
-1.221-0.515-1.201
3.0173.655
34.49127.53522.56118.23911.921
7.749
2.105
2.663
-0.736
0.025
-0.552
-2.957
-0.885
-2.915
-0.338
-0.922
5.4736.159
20.12221.93218.079
4.618
0.979
1.527
0.405
-0.192
0.297
-1.168
-4.809
-7.249
-0.32
-3.491
6.3984.649
20.65516.9112.256
7.4781.494
1.172
0.158
-1.133
-1.196
0.653
-2.238
-3.609
-1.345
-3.257-4.113
-2.492-2.093
22.89920.81213.955
3.7590.6020.223
-1.231
-1.679
-0.696
-3.141
-1.722
-0.488
-3.699
-5.556
-2.06
-2.946
14.06212.8928.211
2.915
1.577-0.627
-1.808
-1.37
-2.565
-2.845
-1.307
-1.76
-1.957
-0.521
-1.184
-0.658
-0.626
8.9676.6783.439
3.369
1.144
-0.76
-0.218
-1.729
-1.523
-1.056
-2.008
-1.722
-0.875
-0.027
-0.345
-0.125
5.435.25
4.5870.77
-1.482
-1.88
-0.828
-1.119
-0.494
-1.926
-1.578
-0.192
-1.226
-2.047
2.9424.2923.041.603
-1.7
-2.311
-2.2
-1.48
-1.615
-1.672
-0.168
-0.0380.078
0.027
1.6881.2281.955
-0.149
-0.55
-2.405
-1.221
-0.914
-1.018
-0.229
-0.959
-0.639
0.35
0.9580.572
0.467
0.309
0.758
-1.479
-0.667
-1.431
-0.938
-0.311
-0.702
0.0210.704
0.393
0.458
-1.604
-0.374
-1.3260.165
-0.187
-1.567
0.6
1.0870.916
-0.878
-0.6
-0.382
-0.917-0.04
-0.105
-0.12
0.2720.372
0.0
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
00
0
0
0
5
061525879919
366674
632
799
84
978
18.50611.53911.0359.3878.455
4.5072.92
2.559
1.6
0.0170.2
13.09410.9128.5667.0315.9534.85
2.467
0.521
0.129
-0.424
-0.565
-0.2680.016-0.455
7.8258.443
13.31710.4538.5727.1414.435
3.362
0.888
1.052
-0.343
-0.34
-0.186
-0.971
-1.247
-1.873
-0.321
-0.168
-1.3210.235
7.3018.2236.952
1.974
0.332
0.44
0.252
-0.113
-0.108
-0.345
-1.742
-1.295
1.205
-1.08
3.853.923
7.7036.3934.716
3.140.766
0.402
0.206
-0.409
-0.632
-0.334
-0.118
-0.774
0.507
0.251-2.051
-0.911-0.916
8.2877.4535.142
1.2160.052-0.021
-0.373
-0.867
-0.285
-0.949
-0.763
-0.518
-1.74
-1.382
-0.645
-1.319
4.9224.473.334
0.906
0.461-0.267
-0.644
-0.727
-0.675
-0.883
-0.525
-0.531
-0.554
-0.586
-0.52
-0.268
-0.256
3.1422.4191.277
0.87
0.363
-0.183
-0.053
-0.548
-0.694
-0.456
-0.422
-0.798
-0.486
-0.087
-0.168
-0.085
0.7321.53
1.3130.229
-0.632
-0.406
-0.528
-0.341
-0.196
-0.454
-0.768
-0.193
-0.503
-0.818
0.5781.1190.6880.69
-0.386
-0.969
-0.891
-0.25
-0.928
-0.694
-0.112
-0.054-0.009
-0.02
0.2390.1040.701
-0.434
-0.519
-0.699
-0.482
-0.506
-0.357
-0.085
-0.244
-0.128
0.086
0.1220.315
-0.181
-0.154
0.086
0.134
-0.289
-0.37
-0.279
-0.188
-0.303
0.0450.077
0.133
-0.115
-0.89
-0.243
-0.671-0.009
-0.211
-0.592
0.015
0.0840.25
-0.521
-0.371
-0.241
-0.341-0.16
-0.165
-0.118
0.053-0.015
-0.0
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
0
0
00
0
0
0
0
0
0
5
433458861
917
085453
286
985
192
413
-15.032-12.103-10.721-8.617-7.436
-4.217-3.039
-2.526
-1.578
-0.855-0.386
-12.128-10.003-7.807-6.213-5.105-4.247-2.576
-0.943
-0.521
-0.149
0.695
0.04-0.010.19
1.912.294
-12.032-9.145-7.492-6.426-4.274
-3.028
-0.885
-0.371
-0.047
0.821
0.21
0.611
1.558
2.647
0.736
0.447
-1.653-3.007
-6.411-7.037-6.115
-1.941
-0.512
0.311
-0.25
0.157
0.347
-0.405
0.833
0.116
3.226
-1.008
2.4892.642
-6.482-4.962-4.117
-2.543-0.958
0.288
-0.116
0.358
0.477
0.501
-0.684
1.107
-0.235
0.6724.127
1.306-2.737
-3.424-5.863-4.286
-1.089-0.4160.094
0.38
0.948
0.254
0.519
1.207
1.711
0.715
0.424
0.868
1.69
-3.986-3.327-2.715
-0.642
-0.719-0.1
0.387
0.806
1
0.757
1.284
0.649
0.59
1.308
-0.063
0.555
0.354
-2.517-1.84-0.932
-0.206
-0.253
0.165
-0.019
0.502
0.632
0.453
0.431
0.947
0.404
0.226
0.13
0.228
-0.428-0.948-0.948-0.186
0.726
0.239
0.766
0.337
0.237
0.469
0.776
0.234
0.431
0.579
-0.175-0.393-0.446-0.591
0.226
0.782
0.968
0.223
0.708
-0.005
0.102
0.0550.025
0.017
0.0590.102-0.553
0.219
0.56
0.61
0.42
0.353
0.213
0.118
0.206
0.092
-0.048
-0.101-0.202
0.323
0.31
-0.044
-0.035
0.236
0.348
0.279
0.202
0.257
-0.0010.029
-0.054
0.196
0.663
0.258
0.6170.104
0.21
0.474
0.055
-0.004-0.142
0.639
0.35
0.252
0.3310.269
0.178
0.147
-0.040.056
0.1
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-10-5
0
0
00
00
0
00
0
5
5
10
435309932059
745343
391
621
784
227
-34.207-26.26-25.339
-19.147-16.078
-9.721-7.073
-5.969
-3.392
-3.24-1.81
-27.513-22.501-17.852-13.746-11.227-9.539-6.55
-2.007
-0.921
-0.329
1.789
0.3010.1340.052
3.994.792
-26.766-20.127-16.329-14.231-9.626
-6.451
-2.641
-0.601
-1.236
1.424
0.169
0.994
2.496
2.469
1.7
1.033
-2.586-4.249
-14.075-13.195-12.427
-4.709
-1.309
1.138
-0.667
0.462
0.758
-0.409
1.542
-0.202
8.972
-1.418
-10.922
-2.53
-14.183-10.56-8.991
-6.249-2.869
0.303
-0.109
0.681
1.045
1.441
-1.205
3.106
0.618
1.3993.537
4.244-11.505
-11.851-12.323-9.111
-2.339-1.4290.152
0.718
1.738
0.246
1.147
2.719
3.495
0.036
-0.272
4.538
4.453
-9.618-7.039-5.695
-0.507
-1.703-0.153
1.093
1.665
2.193
1.745
2.829
1.174
1.594
2.287
0.103
0.848
0.883
-6.384-3.84-2.366
-0.252
-0.755
-0.161
0.043
1.019
1.922
1.033
1.078
2.08
0.974
0.566
0.297
0.554
-1.099-1.954-1.935-0.351
1.638
0.5
2.423
0.604
0.613
0.988
1.648
0.723
1.004
0.901
-0.366-0.761-0.872-1.188
0.318
1.6
2.082
0.532
1.261
0.043
0.263
0.0130.068
0.059
-0.3130.251-1.175
0.32
1.283
1.292
0.997
0.829
0.507
0.334
0.482
0.22
-0.049
-0.188-0.219
0.616
0.789
3.617
-0.099
0.602
0.702
0.7
0.555
0.591
0.0720.093
-0.356
0.353
1.441
0.586
1.5110.317
0.502
0.838
0.166
0.036-0.382
1.212
0.715
0.57
0.720.601
0.45
0.323
-0.0630.135
0.2
-10-7.5-5-2.502.557.510
Fig. 26 Engine out CO2 as compared with CR16.5
Vol.:(0123456789)
SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x Research Article
fuel is needed to achieve the same torque, means less heat energy will be produced which will ultimately result in a lower temperature; reducing the production of NOx.
The effect is more prominent at low load-low rpm conditions while some of its prominence can also be seen at high torque-low rpm values.
5.2.7 Mechanical efficiency
Figure 25 shows that with an increase in compression ratio, there is a slight decrease in the mechanical efficiency of the engine. The opposite is observed when the compres-sion ratio is decreased. Although the percentage change is very small, ME decreases because as CR increases, fric-tional losses of the mechanical components along with some pumping losses also increase (especially in the low torque operational areas). This ultimately results in slightly affecting the overall mechanical efficiency of the engine.
5.2.8 Co2
It can be clearly observed from Fig. 26, that the amount of CO2 produced is inversely proportional to compression
ratio. The effect of this change of compression ratio on this emission is greatly at low torque-low rpm values. This is because at low torque-low rpm the air/fuel mixture (low in quantity as compared to high torque-high rpm) in the cylinder is not homogenously compressed and burnt in the cylinder resulting in a poor combustion.
5.2.9 Soot
Figure 27 shows the effect of compression ratio on the per-centage change in Soot. With an increase in compression ratio, soot increased at a very sharp rate throughout the map except from low torque-low rpm operation condi-tions (where it was observed to decreased). This is because at high torque-high rpm conditions the amount of air needed for a more complete combustion was less than the amount ingested by the engine. Thus, a supercharger can be a suggestive solution to increase the amount of air in the cylinder during high load operational conditions to decrease soot production.
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-50
-50-5
0
-50
-50
-5050
0
0
0
502441
641
93
94
9
29
3122223365
2-66
-66
2434197
40
352721169-1-30
-81
2889
856
865
44-69-92
-100-100
3728242415
2
-7
-29
-56
-75
-41
924
-65
-94
-63
-46
-91-92
242830
6
-6
-14
-25
-39
-36
-50
-6
-49
-77
-77
-94-54
262828
168
3
-7
-15
-27
-97
-32
-87
-62
-96-97
-68-53
433533
1453
-3
-9
-16
-33
-45
-38
-70
-83
-92
-75
423928
14
71
-3
-9
-13
-24
-30
-38
-45
-30
-39
-59
-41
342820
16
7
0
-2
-7
-14
-20
-29
-31
-28
-23
-55
-27
2826216
-2
-5
-8
-14
-18
-29
-28
-22
-68
-60
2622169
-3
-7
-11
-19
-25
-30
-64
-52-45
-33
201311
4
-1
-8
-12
-15
-20
-45
-56
-64
-69
-72-62
11
5
3
-4
-6
-12
-15
-32
-52
-73-79
-94
5
1
-4
-11-17
-29
-57
-85
-94-85
2
-0
-5
-12-20
-32
-47
-68-73
-5
-40
-25
-10
5
20
35
50
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-100
-100
-50
-50
-50
-50
0
0
2870
56
47
74
25
0
1610101220
1-28
-87
377082
-99-87
171411851
-12
-43
270
268
278
-99-85-51
-94-94
191513127
2
-2
-13
-28
-42
-94
-31
-45
-88
-34
-17
-8-22
131414
3
-3
-6
-11
-18
-19
-22
-99
-79
16
-35
-43-25
151413
73
1
-3
-7
-14
-55
-88
-76
-8
-19-64
-34-26
211714
521
-1
-5
-7
-15
-21
-20
-38
-37
-72
-39
171512
5
20
-1
-4
-6
-10
-13
-16
-18
-18
-17
-26
-17
14118
5
2
0
-1
-3
-6
-8
-12
-14
-13
-10
-24
-11
7862
-1
-2
-4
-5
-7
-11
-13
-11
-29
-26
8753
-1
-3
-5
-7
-12
-13
-28
-22-18
-13
643
0
-1
-3
-5
-6
-8
-18
-23
-22
-29
-33-23
3
1
0
-1
-3
-4
-6
-13
-22
-31-36
-46
0
-1
-2
-5-7
-12
-23
-46
-51-44
-1
-1
-2
-5-8
-15
-20
-30-33
-2
-40
-25
-10
5
20
35
50
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-50 0
0
0
50
5
50
100
100
5090
211
9
07
9
56
-17-12-11-11-14
-227
143
307175
175159
-18-15-12-9-6-210
52
1396
-99
-100
22816460
43
-19-16-13-12-8
-3
3
13
31
63
214
709
75
281
57
28
2947
-14-15-14
-4
2
8
12
21
26
11
200
68
239
-11
-28-17
-16-13-12
-7-3
-1
4
8
16
82
115
162
13
65230
53655
-40-16-13
-5-3-1
2
6
7
15
28
36
27
22
126
62
-15-13-10
-4
-3-1
2
5
7
11
18
18
19
31
8
33
19
-12-9-6
-3
-2
0
1
4
6
8
12
16
13
12
23
13
-6-6-5-1
2
2
4
5
7
11
14
10
28
23
-7-4-3-2
1
3
5
7
11
11
28
2016
12
-5-2-3
-0
2
3
4
6
7
17
22
21
27
3021
-2
0
-0
1
3
4
5
11
21
3036
48
0
1
2
56
11
21
51
5751
1
1
2
58
16
18
3133
2
-40
-25
-10
5
20
35
50
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
0
0 00
0
5050
50
50
50
50
50
100
00
100
100
100
100
37252324
399
04
74
39
89
-39-28-28-26-28
-657
379
530410
353370
-40-35-29-23-16-820
133
5846
16
155
803532144
6-0
-44-36-31-28-20
-9
5
33
71
169
658
2582
168
485
160
73
4567
-33-31-30
-10
6
23
29
54
65
37
595
146
1329
-4
123-70
-37-30-28
-17-7
-1
9
20
40
246
352
624
64
171241
2172004
-59-35-29
-11-7-1
5
14
17
37
72
94
33
24
802
207
-33-27-22
-7
-6-1
5
12
18
26
44
40
50
64
22
65
47
-27-20-15
-7
-4
-0
3
9
17
20
28
39
31
28
52
29
-12-13-10-3
5
4
12
12
16
24
34
25
65
45
-15-9-7-5
2
8
12
15
23
23
66
4235
26
-11-5-6
-0
4
7
10
13
16
37
50
46
59
6648
-4
0
5
2
6
9
12
25
46
6882
101
0
2
5
1013
24
45
121
137133
2
2
4
1016
37
40
7077
4
-40
-25
-10
5
20
35
50
Fig. 27 Engine out soot as compared with CR16.5
Vol:.(1234567890)
Research Article SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x
5.2.10 Engine out temperature
Exhaust temperature of the cylinder is directly propor-tional to the amount of combustion. Combustion in turn is directly related to the amount of injected fuel; more fuel would mean more combustion leading to more release of heat energy. Therefore, as shown in Fig. 20, an increase in compression ratio decreases the fuel consumption to achieve the same torque, thus it results in a decrease exhaust temperature as illustrated in Fig. 28.
5.2.11 Engine out pressure
In the early stage design of the engine, the pressure dif-ference between the intake and exhaust manifolds of the engine is always considered and studied with importance, to make sure it remains within an acceptable threshold.
A wide difference could result in malfunctioning of vari-ous engine components. For instance, if the difference is too high, a slight opening of EGR valve could result in mas-sive flow of air to pass by it and could ultimately lead to a malfunction of airflow control.
Figure 29 shows that an increase in compression ratio decreases exhaust pressure because of the phenomenon that less fuel is burnt with an increasing compression ratio to achieve the same operational conditions throughout the map.
5.3 Summary of results based on zones
The engine map was categorized in three zones (as shown in Fig. 30):
Zone 1-covering low load area from low until normal operating rpm values;Zone 2-covering middle load area from normal until high operating rpm values;Zone 3-covering high load area (including rated power) with very high rpm values
As can be seen from Fig. 31, thermal efficiency at high load regions of Zone 2 and Zone 3 is approximately around 40%.
A high compression ratio in these zones only increases it by 0.71% and 0.30% with CR18 and 1.57% and 0.40%
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
30
60
768884905166
50898
739
73
777
037
58.95560.64660.80358.80454.524
37.68429.008
23.153
19.592
12.3779.582
56.25154.46751.16946.40739.74433.35723.54
15.393
11.417
9.612
8.347
7.0286.3225.39
2.2222.304
57.47653.91148.89243.0233.823
26.353
18.349
15.327
10.431
8.947
7.158
4.708
5.496
3.824
4.451
3.561
2.3452.177
47.76846.09640.79
21.119
15.004
12.898
9.778
7.745
6.461
4.776
1.913
0.781
4.131
2.176
0.420.229
47.65141.19133.534
22.9617.174
13.873
9.72
6.937
5.573
5.632
3.627
2.402
3.493
1.8921.817
2.0561.983
48.40144.94334.358
18.53212.85811.885
8.567
5.465
5.701
3.362
3.948
3.933
2.176
0.45
2.453
1.507
36.89633.74526.475
15.324
12.7959.606
7.384
6.389
4.314
3.625
4.186
3.28
2.976
2.952
2.499
2.685
2.328
29.90825.13219.696
14.928
11.098
8.293
7.811
5.826
5.001
4.8
3.327
2.868
2.93
2.977
2.505
2.264
21.27118.11615.44910.074
5.895
5.258
5.702
4.863
4.58
2.866
2.309
2.808
2.169
1.477
16.73415.77912.38210.107
5.659
4.511
4.057
3.195
2.694
1.924
2.62
2.2722.286
1.861
12.59911.26510.073
7.532
5.629
3.91
4.067
3.645
3.072
3.485
2.219
2.143
2.939
3.252.889
7.747
6.746
5.792
3.759
3.984
3.096
3.129
3.273
2.802
3.123.28
2.964
5.512
3.786
3.552
2.4833.794
2.885
2.5
3.519
3.2782.7
3.984
3.626
3.072
2.3673.406
2.858
2.43
2.1682.089
2.0
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
384751685378
824851
35
768
648
449
23.88624.38324.29823.34821.478
15.69111.894
10.129
7.861
5.14.909
22.721.79420.52
18.40215.70513.7219.642
6.581
5.229
4.178
3.472
3.1112.8232.263
1.4941.545
22.68320.91119.13917.20713.225
10.888
7.435
6.29
4.279
3.58
2.961
2.072
1.783
1.217
1.711
1.58
0.7390.755
18.27617.85216.083
8.67
5.923
5.149
4.075
3.123
2.589
2.036
0.949
1.113
1.909
1.01
0.4950.494
18.17715.79513.294
9.1256.831
5.409
4.109
2.885
2.255
2.015
1.897
1.378
1.822
1.5660.424
0.9460.738
18.19316.58413.074
6.8965.0054.602
3.49
2.207
2.222
1.482
1.453
1.386
0.638
0.687
1
0.44
13.60912.29510.248
5.622
4.7383.699
2.85
2.317
1.918
1.458
1.56
1.327
1.199
0.951
0.902
1.013
0.889
10.9349.1787.33
5.164
4.06
3.175
2.894
2.189
1.746
1.696
1.475
0.968
1.011
1.09
0.936
0.852
6.7476.2935.1673.637
2.117
2.17
1.853
1.809
1.624
1.19
0.737
1.003
0.739
0.474
5.5395.1834.0293.635
2.154
1.514
1.353
1.33
0.735
0.682
0.923
0.8190.823
0.696
3.9663.5543.353
2.339
1.711
1.46
1.318
1.134
1.077
1.186
0.835
0.728
0.973
0.9681.039
2.261
1.994
1.809
1.703
1.303
1.112
1.092
1.03
0.89
1.0340.956
0.958
1.512
1.041
1.121
0.7561.172
0.853
0.674
1.116
0.8790.882
0.939
0.978
0.921
0.7550.938
0.903
0.7
0.6720.56
0.5
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-5.55367.02133
173037
272
736
029
792
-22.817-23.31-22.743
-21.348-19.714
-14.734-12.032
-9.959
-7.936
-5.864-5.111
-21.656-20.538-18.895-16.861-14.445-12.485-9.446
-6.889
-5.361
-4.545
-3.377
-3.139-2.789-2.361
-2.005-1.958
-21.116-18.932-16.991-15.444-12.547
-9.897
-7.153
-5.713
-4.386
-3.134
-2.864
-2.268
-1.479
-0.659
-1.449
-1.306
-1.136-0.775
-16.527-15.55-14.277
-7.996
-5.638
-4.283
-3.926
-2.941
-2.399
-2.354
-1.432
-1.682
-0.054
-1.942
-1.876-1.828
-15.998-13.54-11.756
-8.349-6.259
-4.699
-3.756
-2.819
-2.292
-1.865
-2.243
-1.136
-1.604
-1.1010.978
-0.5540.819
-11.241-13.848-11.161
-6.173-4.892-4.163
-3.2
-2.029
-2.061
-1.624
-1.04
-0.504
-0.959
-1.002
-0.733
-0.071
-11.597-10.208-8.536
-4.928
-4.423-3.568
-2.675
-2.033
-1.508
-1.335
-0.875
-1.08
-0.992
-0.428
-1.062
-0.701
-0.723
-9.154-7.618-6.04
-4.094
-3.48
-2.775
-2.535
-1.882
-1.508
-1.439
-1.227
-0.695
-0.925
-0.892
-0.855
-0.668
-5.554-4.939-4.187-3.119
-1.764
-1.964
-1.357
-1.499
-1.336
-0.969
-0.626
-0.833
-0.647
-0.489
-4.378-3.82-3.237-2.971
-1.898
-1.328
-0.983
-1.113
-0.687
-1.039
-0.82
-0.724-0.728
-0.651
-3.025-2.71-2.748
-2.03
-1.396
-1.211
-1.053
-0.992
-0.953
-0.949
-0.727
-0.668
-0.801
-0.795-0.82
-1.729
-1.514
-1.564
-1.407
-1.129
-0.893
-0.849
-0.804
-0.717
-0.79-0.701
-0.721
-1.178
-0.956
-0.984
-0.688-0.915
-0.686
-0.508
-0.798
-0.648-0.663
-0.573
-0.826
-0.815
-0.653-0.651
-0.702
-0.509
-0.534-0.422
-0.3
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-25-15
-5
-5
7931.6933193
809186
337
855
636
697
-52.006-51.596-51.799-48.212-43.552
-34.022-27.622
-23.274
-18.538
-14.732-12.889
-49.143-46.614-43.02
-37.826-32.442-28.574-22.301
-15.787
-12.448
-10.387
-7.786
-7.113-6.395-5.811
-4.64-4.585
-47.31-42.416-37.867-34.628-28.024
-22.072
-16.825
-12.826
-10.887
-7.504
-6.767
-5.484
-3.96
-3.497
-3.296
-2.98
-2.92-2.453
-36.837-33.074-31.147
-18.21
-12.871
-9.645
-9.196
-6.7
-5.527
-5.138
-3.542
-4.084
1.311
-4.049
-0.435
-6.084
-35.382-29.629-26.029
-19.235-14.223
-10.946
-8.517
-6.719
-5.348
-4.163
-4.946
-2.361
-3.144
-2.62-0.952
-0.3591.625
-28.704-29.78-24.179
-13.708-11.284-9.386
-7.26
-4.947
-4.873
-3.72
-2.414
-1.463
-2.948
-2.927
-0.256
0.304
-24.612-22.127-18.435
-10.415
-9.79-7.877
-5.834
-4.614
-3.407
-2.954
-1.96
-2.6
-2.012
-1.306
-2.233
-1.733
-1.578
-19.007-16.486-13.403
-9.031
-7.903
-6.517
-5.552
-4.233
-3.004
-3.137
-2.628
-1.569
-2.003
-1.983
-1.896
-1.483
-12.252-10.822-9.088-6.869
-3.997
-4.372
-2.506
-3.383
-2.87
-2.186
-1.449
-1.729
-1.416
-1.325
-9.631-8.365-7.104-6.449
-4.327
-3.077
-2.206
-2.422
-1.721
-2.239
-1.821
-1.682-1.656
-1.485
-6.57-6.052-6.079
-4.657
-3.111
-2.756
-2.27
-2.148
-2.065
-2.026
-1.597
-1.496
-1.728
-1.74-1.669
-4.198
-3.518
-1.783
-3.273
-2.537
-2.098
-1.799
-1.708
-1.536
-1.666-1.503
-1.697
-2.908
-2.38
-2.388
-1.638-2.059
-1.545
-1.201
-1.644
-1.369-1.524
-1.677
-2.133
-2.038
-1.65-1.487
-1.468
-1.132
-1.179-0.951
-0.8
-10-7.5-5-2.502.557.510
Fig. 28 Engine out temperature as compared with CR16.5
Vol.:(0123456789)
SN Applied Sciences (2019) 1:1162 | https://doi.org/10.1007/s42452-019-1185-x Research Article
with CR20. Thus, this change is not as much as can be observed at low load conditions, where normal thermal efficiency was around 25% and was observed to increase by 9.70% at CR20.
The summary of the percentage changes in the values in the three different zones can be seen in Figs. 32, 33 and 34.
BSFC decreases by 8.14%, 1.54% and 0.37% in Zone 1, 2 and 3 respectively when compression ratio is 20. Observing changes in emissions at the same set point, it
CR:13 CR:15
CR:18 CR:20
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
5
5
5
5
5
5
55
5
655636816133
039428
006
561
381
853
1.48821.71692.04772.48213.1592
3.54123.9807
4.5038
4.1608
6.17886.5868
1.40511.61771.87162.48033.41244.01314.846
6.369
7.7142
5.0992
4.7104
4.52864.71095.2222
8.36658.294
1.76872.2832.78013.13573.7603
4.7627
6.1698
5.2762
6.2263
4.9757
4.2423
5.4801
4.0943
5.4225
3.6204
3.6656
4.22584.221
2.33953.19253.6288
5.33
6.2674
5.4425
4.9807
4.2851
3.3758
3.7137
5.4543
7.6051
2.8266
4.7762
5.26885.1861
2.81313.39533.6294
4.76976.0623
5.4987
5.0237
5.1315
4.3797
2.5441
4.0464
4.8304
3.3101
4.55775.6612
4.39634.0082
2.9994.02964.6073
6.44067.45616.7172
6.1973
4.9875
4.1031
5.1698
4.2139
3.1529
5.3861
6.4768
4.1533
4.7643
3.10153.83455.1278
5.5898
6.08596.1952
6.2124
5.6066
5.8187
5.4663
4.4339
4.5921
4.6853
2.9375
3.3413
2.962
2.6977
3.45313.90844.8134
4.287
4.907
5.0687
4.5792
5.6831
5.32
4.9054
4.9005
4.1405
3.3561
2.3853
2.4033
2.1951
4.55654.57624.48195.1919
4.7199
4.7298
4.4242
5.2024
3.9515
4.592
3.4944
2.266
3.4854
4.5047
4.25413.60884.65815.0509
5.0678
4.8521
5.1577
4.1335
4.1481
3.5764
2.2657
1.92161.9077
1.5215
3.25713.92094.1306
5.1101
4.1852
5.2625
3.9496
3.6545
3.6581
3.0802
3.0219
2.7913
2.2206
2.00742.116
2.1933
3.0777
2.3903
3.9975
3.478
3.5911
3.2142
2.9833
3.2537
3.01732.1855
2.2192
2.0031
3.6063
2.3766
3.14433.2974
2.1133
4.1755
2.3274
1.48891.1667
2.6273
2.4556
2.1104
2.61893.1296
2.4873
2.185
1.32421.1371
1.47
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
925818765774
258528
575
796
377
358
0.60680.70250.77610.95911.2783
1.40851.68
1.8543
1.708
2.51292.4709
0.57750.61050.72881.00481.28941.55161.8562
2.5439
2.6635
1.9244
1.9462
1.72951.75262.095
2.59972.5592
0.70170.85781.03791.17791.523
1.6959
2.3958
2.0711
2.4489
2.1777
1.6616
2.029
2.1434
2.5433
1.5521
1.3442
1.82311.8075
0.85311.17091.3484
1.9752
2.3956
2.0286
2.1258
1.6524
1.4854
1.4129
2.0192
1.8332
0.7317
1.6256
1.67191.591
1.05561.21771.3827
1.8532.1115
2.0519
1.8579
1.9672
1.8171
1.3681
1.1467
1.4945
0.5933
0.77952.3348
1.65941.6046
1.08011.37751.6523
2.35022.914
2.4887
2.2449
2.0671
1.5418
1.7711
1.5952
1.4073
2.1354
1.8359
1.3982
1.8575
1.09291.30981.641
2.0048
2.20112.3298
2.1656
2.1302
1.9204
1.7905
1.5855
1.5654
1.4875
1.3677
1.2492
1.0879
1.0046
1.15831.26621.58
1.5369
1.6929
1.7615
1.5642
1.8691
1.8566
1.6987
1.4842
1.5569
1.3315
0.9106
0.9003
0.838
1.51361.50621.52441.734
1.6848
1.4535
1.5643
1.7603
1.3164
1.3728
1.3546
0.8949
1.2203
1.5797
1.31881.12781.55541.4977
1.5276
1.7127
1.705
1.1586
1.6211
1.3215
0.7891
0.69410.6837
0.5691
0.9231.1791.1156
1.8102
1.5338
1.5913
1.256
1.2813
1.1694
0.9793
0.8853
0.7264
0.7041
0.76570.5523
0.6127
0.8905
0.7538
0.7929
1.084
1.0163
0.9548
0.9329
1.0352
0.80310.7398
0.6218
0.5443
1.2716
0.7459
1.14610.9104
0.7282
1.1945
0.9042
0.59520.3864
0.6017
0.6615
0.6295
0.75160.8641
0.8603
0.6366
0.35970.3637
0.3
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
902279968
831
349606
506
192
454
949
-0.5562-0.6713-0.7835-0.8956-1.0859
-1.3914-1.5641
-1.8512
-1.5948
-2.1705-2.5151
-0.5467-0.6088-0.6788-0.8296-1.2298-1.4227-1.8222
-2.1879
-2.3504
-1.6197
-1.8812
-1.5517-1.6979-1.8596
-1.9195-1.9569
-0.6134-0.7448-0.8883-1.0426-1.2728
-1.5194
-2.2592
-1.9598
-2.0471
-2.2093
-1.5594
-1.7063
-2.149
-2.7809
-1.6885
-1.433
-1.3572-1.6017
-0.7923-0.9906-1.1753
-1.7471
-1.9522
-2.1546
-1.9136
-1.5326
-1.5124
-0.9622
-1.4444
-1.0674
-2.6819
-0.3396
-0.3701-0.3649
-0.9394-1.0402-1.1788
-1.738-1.7275
-2.105
-1.675
-1.7833
-1.6054
-1.3811
-0.6613
-1.576
-0.6968
-1.2747-3.2091
-1.7384-2.7728
-0.6665-1.0819-1.3334
-1.9177-2.2542-2.1165
-1.9404
-1.9023
-1.3621
-1.3696
-1.6703
-1.9945
-1.2498
-1.0507
-1.3807
-1.9218
-0.8891-1.0435-1.2636
-1.686
-1.9421-1.7352
-1.6943
-1.8572
-1.8331
-1.4831
-1.8073
-1.4065
-1.247
-1.6704
-0.6844
-1.1364
-0.9578
-0.8813-0.9861-1.239
-1.3577
-1.3486
-1.4386
-1.2131
-1.5086
-1.5017
-1.3915
-1.2231
-1.4329
-1.0827
-0.859
-0.7493
-0.8278
-1.1844-1.1739-1.1883-1.316
-1.4637
-1.1211
-1.3977
-1.384
-1.0753
-1.1337
-1.1928
-0.7742
-1.007
-1.1912
-0.9961-0.954
-1.1649-1.0426
-1.1482
-1.3324
-1.3285
-0.9054
-1.2165
-0.6647
-0.6571
-0.5831-0.5919
-0.5111
-0.6587-0.8381-0.9391
-1.2704
-1.2902
-1.2449
-0.9631
-0.9331
-0.8159
-0.7762
-0.7067
-0.5819
-0.5562
-0.5636-0.4471
-0.4512
-0.6574
-0.6086
-0.6606
-0.8275
-0.7976
-0.7176
-0.7158
-0.7775
-0.5784-0.5906
-0.4673
-0.4165
-0.9294
-0.6644
-0.9931-0.7237
-0.5733
-0.8405
-0.6536
-0.4428-0.3028
-0.3666
-0.5247
-0.5609
-0.633-0.6692
-0.6073
-0.4629
-0.2283-0.2728
-0.27
-10-7.5-5-2.502.557.510
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
-5
-5
-5
-5-5
427363252
864
86108
464
154
648
427
-1.2894-1.4876-1.7158-2.0198-2.4505
-3.1968-3.6528
-4.2417
-3.7388
-4.7467-5.5249
-1.1735-1.3422-1.5141-1.9033-2.6126-3.2056-4.0889
-4.9624
-5.5371
-3.7199
-4.3127
-3.6357-3.9699-3.9756
-4.3843-4.4206
-1.3791-1.6996-2.0103-2.3609-2.7857
-3.4654
-4.748
-4.443
-4.3583
-4.7355
-3.444
-3.6461
-4.2814
-4.325
-3.8109
-3.2588
-2.8577-3.1227
-1.7062-2.1023-2.5105
-3.7124
-4.2324
-4.9909
-4.229
-3.4912
-3.3843
-2.48
-3.0973
-2.1696
-7.0352
-1.2894
-3.9414
-8.0548
-2.0013-2.277-2.5774
-3.5669-3.5842
-4.455
-3.8023
-3.9664
-3.633
-3.279
-1.7145
-3.8329
-2.2467
-2.7748-3.8976
-4.5435-5.6333
-1.6082-2.3102-2.8243
-4.1583-4.5481-4.5226
-4.1369
-3.9129
-2.8932
-3.0211
-3.6755
-4.1786
-1.793
-1.5951
-4.5664
-4.5993
-1.8417-2.234-2.6907
-3.5298
-4.0468-3.7365
-3.7808
-3.9094
-3.9935
-3.2151
-3.801
-2.8602
-2.8405
-3.2011
-1.6565
-2.191
-2.1694
-1.8078-2.0651-2.4744
-3.0445
-2.7957
-2.8193
-2.6486
-3.1659
-3.4711
-2.969
-2.6779
-3.0552
-2.3678
-1.9093
-1.6305
-1.8476
-2.4067-2.532
-2.5572-2.8423
-3.1528
-2.4256
-3.3542
-2.828
-2.331
-2.3871
-2.5142
-1.8102
-2.2152
-2.2465
-2.0775-2.0647-2.5329-2.2484
-2.3937
-2.8213
-2.8059
-1.9432
-2.388
-1.4281
-1.451
-1.1755-1.3423
-1.1535
-1.404-1.8458-2.0644
-2.6565
-2.757
-2.6563
-2.0973
-2.0158
-1.7545
-1.6587
-1.5349
-1.2891
-1.2276
-1.2117-1.1149
-1.0912
-1.6214
-3.7932
-1.5341
-1.9043
-1.8604
-1.5123
-1.6025
-1.6603
-1.2457-1.2513
-0.7702
-1.0294
-2.1653
-1.6212
-2.417-1.7179
-1.3043
-1.6062
-1.3405
-0.9379-0.5899
-0.891
-1.3189
-1.4371
-1.5377-1.499
-1.285
-0.9945
-0.5187-0.6161
-0.6
-10-7.5-5-2.502.557.510
Fig. 29 Engine out pressure as compared with CR16.5
Fig. 30 Zones in engine map
900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500N [1_min]
MD
[Nm
]
0
50
100
150
200
250
300
350
400
450
500
6 8 10 12 14 16 18 2022
242628
30
32
34
36
36
38
38
38 40
0
10
20
30
40
50
Fig. 31 Thermal efficiency at CR16.5
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is seen that NOx decreases by 8.33%, CO2 by 8.50% while Soot increases by 6.91%. This clearly suggests that a higher compression ratio should be preferable in Zone 1.
Observing soot and BSFC values with CR20 in Zone 2 and 3 clearly suggest that it is not preferable as a good trade-off. Soot values clearly suggest that a low compres-sion ratio is preferable for Zone 2 and 3. For a smooth tran-sition between Zone 1 and 2, a compression ratio lower than 18 for Zone 2 may result in a sudden jerk produced by the engine. Keeping this in mind, a compression ratio of 18 is preferred for Zone 2.
The transition of compression ratios between the zones is always kept as smooth as possible to avoid any sudden unwanted behaviour from the engine.
Finally, to keep up with the smoothness trend and to avoid any further decrease in performance, the default compression ratio of 16.5 is preferred in Zone 3.
6 Summary/conclusions
The main effect of an increase in compression ratio, was found to be, as expected, a decrease in brake specific fuel consumption (BSFC) and increase in thermal effi-ciency. However, this trend comprised on the best effi-ciency-emissions trade-off for low rpm-low load region of the map (Region 1). With an increase in load and rpm
Fig. 32 Average percentage change in Zone 1 as compared to CR16.5
Fig. 33 Average percentage change in Zone 2 as compared to CR16.5
Fig. 34 Average percentage change in Zone 3 as compared to CR16.5
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(Region 2 to Region 3), the trade-off gap between effi-ciency and emissions becomes wide off since soot starts to become a prominent factor leading to uncompromis-able level.
Assuming, that the instantaneous VCR changing tech-nology can be utilized in the engine, this work found the best combination of compression ratios around the engine load map, giving a best fit of trade-offs of the engine.
The developed numerical model of the engine proved to be a great help in studying VCR concept on an existing engine and proved that numerical modelling can save a lot of expenses in studying concepts like these in the develop-ment phase of the vehicle. However, there are some limita-tions to the numerical model approach such as; not having a complete insight of all the emissions, as improving one factor of emission can prove to vastly effect the emissions which are not given by the numerical model. Moreover, the aging factor of the engine also could not be taken into account using this approach.
The following generalized conclusions can be written from the study performed during experimental work and presented modelling:
• Numerical modelling can greatly aid in getting an idea on the engine being developed at initial stages before the prototype becomes available. The numerical model can also be used in calibration of the engine if soft-ECU is developed in the model;
• An engine equipped with VCR technology can increase the efficiency and decrease the emissions at different operational conditions;
• Increasing compression ratio at low load operations highly increases the thermal efficiency and decreases NOx. At the same time, soot emissions increase in the same operational conditions;
• Future vehicles with the concept of ‘one engine all fuels–one fuel all engines’ will be key option in devel-opment of future transport in the world.
Acknowledgements First, I would like to thank my family for support-ing me at all times. I would also like to thank everyone at Marmara University and AVL Research and Engineering Turkey for a nice and stimulating time, especially to my supervisor, Prof. Dr. M. Zafer Gül and Department Manager, Mr. Caner Bayburtlu for their encourage-ment and valuable ideas. Further, I would like to thank Ramazan Şener for all help in the lab, and Oğuz Ulutürk for his precious time and aid in modelling of the engine. Furthermore, I would like to thank BAPKO (Bilimsel Araştirma Proje Komisyonu) for their support through Project Number: FEN-C-YLP-200318-0113.
Compliance with ethical standards
Conflict of interest On behalf of all authors, the corresponding au-thor states that there is no conflict of interest.
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