THE POTENTIAL OF DUAL STAGE TURBOCHARGING AND MILLER CYCLE ... · GT-Suite Users International...
Transcript of THE POTENTIAL OF DUAL STAGE TURBOCHARGING AND MILLER CYCLE ... · GT-Suite Users International...
GT-Suite Users International ConferenceFrankfurt a.M., October 4th 2004
THE POTENTIAL OF DUAL STAGE TURBOCHARGING
AND MILLER CYCLE FOR HD DIESEL ENGINES
F. MILLO, F. MALLAMO, A. CAFARI (Politecnico di Torino)
G. GANIO MEGO (IVECO S.p.A)
Presentation overview
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of the simulation for the analysis of
possible performance enhancements
• Conclusions
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
INTRODUCTION
The search for further enhancements of the specific power output of Heavy Duty Diesel engines has encouraged several manufactures to exploit possible ways to increase the boost level while maintaining peak firing pressure as well as pollutant emissions within acceptable limits.
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
INTRODUCTION
While dual stage turbocharging provides indeed a suitable method to achieve a significant increase of the boost level (as well as a wider operating range, due to its higher flexibility), it may nevertheless lead, due to the extremely high values of the combustion pressure, to unbearable loadings on some engine components, as well as to an unacceptable increase of NOx emissions.
Therefore, the increase in the boost pressure that can be achieved by means of dual stage turbocharging, should usually be coupled with measures aiming to maintaining the peak firing pressure within acceptable levels, such as, for instance, reductions of the engine compression ratio and/or of the injection advance.
However, these countermeasures may lead to significant penalties as far as fuel specific consumption and soot emissions are concerned, requiring a careful pro vs. cons analysis, in order to find out a proper trade-off.
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
INTRODUCTIONOn the other hand, if the increase in boost level is carried
out in combination with an Early Intake Valve Closure, followed by an in-cylinder expansion of the charge during the last portion of the intake stroke (Miller cycle), significant reductions in peak firing pressure and temperature can be achieved, thus diminishing both pressure and thermal loadings on engine components, as well as NOx emissions, which are extremely sensitive to the combustion temperatures.
Standard Miller
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
INTRODUCTION
Standard Miller
For instance, if the air temperature at engine intake can be assumed to be independent from the boost pressure, and if the boost level in the Miller cycle is increased so to reach the same in-cylinder pressure at the beginning of the compression stroke of a "standard" turbocharged engine, equal end-of-compression pressure levels will be attained in both engines, but with lower temperatures in the Miller cycle, as well as with an increased trapped mass of air, which will allow, at constant air/fuel ratio, an increase of the injected fuel quantity and therefore of the engine power output.
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
INTRODUCTIONAlthough the Miller cycle concept is well known from the
1950s, and has found several applications for different types ofengines with the main target of increasing the power output while maintaining within acceptable limits mechanical and thermal loadings, the potential for remarkable reductions of NOx emissions has strongly renewed the interest in this technique in the last decade.
However, even if the simulation tool plays a fundamental role for the evaluation of the potential of the Miller cycle, its advantages can only be assessed through a complete and detailed engine model, since several interacting effects have tobe taken into account, such as, for instance:
- effects on the gas exchange process, due to the higher engine backpressure which is needed to operate the turbocharger at higher boost levels;
- effects of boost level enhancement and of the correlated actions (reductions of the injection advance and/or the engine compression ratio) on the combustion process and on the pollutant formation in particular.
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
INTRODUCTION
Therefore GT-POWER (with the EngCylCombDIJet model
activated for the analsyis of the combustion process) was
applied to evaluate the potential of dual stage turbocharging
and Miller Cycle for a 6 cylinders in line, 13 litres displacement,
HD diesel engine (IVECO CURSOR 13).
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
EXPERIMENTAL SET-UP
MAIN ENGINE FEATURES
397 kW at 1900 rpmMaximum Power
4 valves/cylinderValves
Direct injection with Unit Pump Injectors
Fuel Metering System
Single Stage Turbocharger with Variable Geometry Turbine (VGT) and Aftercooler
Air Intake System
2356 Nm at 1000 rpmMaximum Torque
17 : 1Compression Ratio
12,8 dm3Displacement
135 / 150 mmBore/Stroke
Diesel, 4 stroke6 cylinders in line
Type
• boost level 3 bar
• bmep 23 bar
• spec. output 31 KW / dm3
IVECO CURSOR 13
Several different applications (e.g. trucks, gensets, marine etc.).
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
EXPERIMENTAL SET-UP
Temp. meas.
Temp. meas.
Pressure meas.
While the experimental activity and the baseline model validation were carried out on the HD truck engine, the analysis of the dual stage turbocharging and Miller cycle were carried out for a genset engine, at constant revolution speed (1500 rpm) and full load operating conditions.
Experimental investigations were carried out under full loadoperating conditions over a speed range from 800 up to 2200 rpm, recording in-cylinder and fuel injection pressure traces were recorded, along with injector needle lifts.
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
THE ENGINE MODEL
AFTERCOOLER
INTAKE
MANIFOLD
EXHAUST
MANIFOLD
TURBOCHARGER
In the baseline model heat release profiles obtained by the analysis of experimental in-cylinder pressure traces were used
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
BASELINE ENGINE MODEL VALIDATION
0
500
1000
1500
2000
2500
700 900 1100 1300 1500 1700 1900 2100 2300Engine speed [rpm]
Air
Mas
s Fl
ow [k
g/h]
EXPSIM
AIR MASS FLOW
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
BASELINE ENGINE MODEL VALIDATION
TURBOCHARGER SPEED
60
70
80
90
100
110
700 900 1100 1300 1500 1700 1900 2100 2300Engine speed [rpm]
Turb
o Sp
eed
[Krp
m]
EXPSIM
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
BASELINE ENGINE MODEL VALIDATION
BOOST PRESSURE
1.8
2
2.2
2.4
2.6
2.8
3
3.2
700 900 1100 1300 1500 1700 1900 2100 2300Engine speed [rpm]
Boo
st P
ress
ure
[bar
]
EXPSIM
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
BASELINE ENGINE MODEL VALIDATION
10
12
14
16
18
20
22
24
700 900 1100 1300 1500 1700 1900 2100 2300Engine speed [rpm]
BM
EP [b
ar] EXP
SIM
BMEP
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
ENGINE MODEL VALIDATION
The baseline engine model could be used to obtain a first estimate of the enhancement of engine performance that can be attained by means of dual stage turbocharging, for instance by increasing the injected fuel quantity while maintaining the same Air/Fuel ratio of the reference single-stage turbocharged engine.
However, in order to allow a reliable prediction of the effects of boost level enhancement and of the correlated actions (reductions of the injection advance and/or the engine compression ratio) on the combustion process and on the pollutant formation, a refinement of the baseline model was carried out, by means of the multi-zone combustion model for NOx and PM prediction, provided by the EngCylCombDIJet feature.
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
REFINED ENGINE MODEL VALIDATION
NOx EMISSIONS AND PEAK FIRING PRESSURES
0
500
1000
1500
2000
2500
3000
700 900 1100 1300 1500 1700 1900 2100 2300Engine speed [rpm]
NO
x [g
/h]
100
125
150
175
200
225
250
Peak
pre
ssur
e [b
ar]
NOx EXPNOx SIMPeak pressure SIMPeak pressure EXP
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
REFINED ENGINE MODEL VALIDATION
SOOT EMISSIONS
0
10
20
30
40
50
60
70
700 900 1100 1300 1500 1700 1900 2100 2300Engine speed [rpm]
Soot
[g/h
]
Soot EXPSoot SIM
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
REFINED ENGINE MODEL VALIDATION
NOX - SOOT EMISSIONS(CONSTANT SPEED 1570 RPM, VARIABLE LOAD)
0
500
1000
1500
2000
2500
20 25 30 35 40 45A / F [-]
NO
x [g
/h]
0
10
20
30
40
50
Soot
[g/h
]
NOx EXPNOx SIMSoot EXPSoot SIM
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
WASTE GATE VALVE
Low pressure Turbocharger
High pressure Turbocharger
Aftercooler
• Analysis carried out for a genset engine, at constant revolution speed (1500 rpm) and full load operating conditions
• Intercooler between the LP and HP turbocharger stages discarded, mainly because the corresponding higher pressure losses in the circuit were not compensated by remarkable savings in the compression work of the HP stage
• Boost level controlled bymeans of a waste-gate valve on the HP turbine: for genset application, HP turbine characteristics redesigned
DUAL STAGE TURBOCHARGING
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
WASTE GATE VALVE
Low pressure Turbocharger
High pressure Turbocharger
Aftercooler
Injected fuel quantity limitedtrying to fulfil the following requirements:
•peak firing pressures below 180 bar, aiming to a target levelequal to or lower than 160 bar(possibly without injection timing retards, to avoid detrimental effects on bsfc), to maintain the same stress levels as in the "reference" single stage turbocharged engine.
• A/F ratio values equal to or higher than those of the "reference" single stage turbocharged engine, so to avoid penalties in soot emissions.
DUAL STAGE TURBOCHARGING
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGING
73.9 77.2 77.273.9 73.5
0102030405060708090
100
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[kg/
h]
BMEP FUEL FLOW
BOOST PRESSURE PEAK PRESSURE
05
101520253035
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[bar
]
23.4 24.522.8
24.323.5
2.93.2 3.0
3.43.5
0.00.51.01.52.02.53.03.54.04.55.0
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[bar
]
158 157 164180171
0
50
100
150
200
250
300
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[bar
]
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGINGA/F
23.4 23.9 23.0
27.6 27.1
05
10152025303540
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[-]
BSFC
200.9 198.3 196.9197.0 195.8
0
50
100
150
200
250
300
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[g/k
Wh]
Specific SOOT Emissions
0.0430.035
0.044
0.017 0.019
0.000.010.020.030.040.050.060.070.080.090.10
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[g/k
Wh]
Specific NOX Emissions
5.35.9 6.05.8 5.8
0123456789
10
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[g/k
Wh]
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGING + HP TURBINE OPT.
0
10
20
30
40
50
60BMEP [bar]
P max [MPa]
BSFC/10 [g/kwh]
A/F [-]
Spec.NOx*10 [g/kwh]
Spec.SOOT*1000 [g/kwh]
Reference
CR 17
CR 16
+ 5,5% CR16
+ 6,2 % CR17
- 1,2% CR16
- 2 % CR17
157 CR16
164 CR17
+ 11% CR16
+13 % CR17
- 18% CR16
+ 2 % CR17
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGING +
MILLER CYCLE
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGING + MILLER CYCLEBMEP
22.8 23.4 23.5 24.3 24.524.3 24.1
0.0 0.0 0.00
5
10
15
20
25
30
35
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[bar
]
FUEL FLOW
PEAK PRESSURE
158 157 164180
171160160
0
50
100
150
200
250
300
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[bar
]Miller Supercharging
73.9 77.2 77.273.9 73.576.6 75.4
0102030405060708090
100
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[kg/
h]
Miller Supercharging
BOOST PRESSURE
2.93.2 3.0
3.53.43.5 3.6
0.0
1.0
2.0
3.0
4.0
5.0
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[bar
]
Miller Supercharging
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGING + MILLER CYCLEA/F
23.4 23.9 23.0
27.6 27.125.6 24.0
05
10152025303540
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[-]
Miller Supercharging
BSFC
200.9 198.3 196.9195.8197 196.6 195.3
0
50
100
150
200
250
300
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[g/K
wh]
Miller Supercharging
Specific NOX Emissions
5.35.9 6.0
5.0 4.7
5.85.8
0123456789
10
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[g/K
wh]
Miller Supercharging
Specific SOOT Emissions
0.0430.035
0.044
0.0190.017
0.0350.025
0.000.010.020.030.040.050.060.070.080.090.10
Reference CR 16 CR 17 CR 16 + HPturbine opt.
CR 17 + HPturbine opt.
[g/K
wh]
Miller Supercharging
ANALYSIS OF POSSIBLE PERFORMANCE ENHANCEMENTS
DUAL STAGE TURBOCHARGING + MILLER CYCLE
0
10
20
30
40
50
60BMEP [bar]
P max [MPa]
BSFC/10 [g/kwh]
A/F [-]
Spec.NOx*10 [g/kwh]
Spec.SOOT*1000 [g/kwh]
Reference
CR 17
CR 16
+ 5,5% CR16
+ 4,7 % CR17
- 2,1% CR16
- 2,7 % CR17
160 CR16
160 CR17
- 6 % CR16
-11% CR17
- 41% CR16
- 18 % CR17
• Introduction
• Experimental set-up
• The engine model
• Engine model validation
• Use of thesimulation for theanalysis of possibleperformance enhancements
• Conclusions
CONCLUSIONS
The potential of dual stage turbocharging and Miller Cycle for a 6 cylinders in line, 13 litres displacement, HD diesel engine was analysed, by means of a 1-D engine simulation fluid dynamic code, coupled with a multi-zone combustion model for NOx and PM prediction.
After a detailed validation process, based on an extensive experimental data set, the engine model was then used to predict the effects on engine performance and emission characteristics of different combinations of dual stage turbochargers, engine compression ratio values and intake valve lift profiles.
The potential for an appreciable increase (about 5%) in the engine power, with a slight decrease in the specific fuel consumption (about 2%) and a remarkable decrease of NOxspecific emissions (up to 10%) was demonstrated.
Acknowledgments
The authors wish to thank Dr. Jean-Louis Jolissaint
(IVECOMotorenforschung) for kindly providing most of the experimental
data which were used for the model validation, and prof. Carlo Ferraro
(Politecnico di Torino) and Dr. Sten Isaksson (Wartsila) for their
valuable suggestions concerning the simulation of the Miller cycle.
GT-Suite Users International ConferenceFrankfurt a.M., October 4th 2004
THE POTENTIAL OF DUAL STAGE TURBOCHARGING
AND MILLER CYCLE FOR HD DIESEL ENGINES
F. MILLO, F. MALLAMO, A. CAFARI (Politecnico di Torino)
G. GANIO MEGO (IVECO S.p.A)