s lidi

1-15

h i g h l i g h t s

Exhaust temperature increase by 6.5%, 6.5%, 7reases b4.7%, 1%, 10.5

use computational developed code which uses the results of combustion and

behavior in Soot and NOx emissions production, it is essential toemployee an appropriate methodology to reduce the correspond-ing emissions [1]. Some of the useful technologies to reduce theSoot and NOx, which have been adopted so far, include high-pres-sure fuel injection, multiple injections, advancing and retarding thefuel injection time and using swirl with higher intensity [28]. In

re studied morethe rst aoncept in tamental c

energy availability, which has been introduced in [13]. For aing the performance of engine subsystems, exergy analysis cuseful alternative to energy analysis, because it is able tomore information about engine processes [1416]. Over the years,many reports have been published on details over the use of thesecond law of thermodynamics with respect to internal combus-tion engines [1720]. A summary of other studies on the subjectof DI and IDI diesel engine was provided below.

Jafarmadar and Zehni [21] carried out a numerical analysisabout the effect of dwell time duration in a two-stage injection

Corresponding author. Tel.: +98 441 2972000; fax: +98 441 2773591.E-mail address: s.jafarmadar@urmia.ac.ir (S. Jafarmadar).

Fuel 154 (2015) 123131

Contents lists availab

Fue

.ethan other engines due to their higher efciency. Although NOxand Soot emissions generated in these engines are higher thanthose of Indirect Injection (IDI) diesel engine, but there are utilitar-ian technologies to reduce these emissions. Due to contrasting

tion, the combustion and emission processes athoroughly these days, implemented by applyingond laws of thermodynamics. Exergy is the key cond law analysis; that has roots in more fundhttp://dx.doi.org/10.1016/j.fuel.2015.03.0260016-2361/ 2015 Elsevier Ltd. All rights reserved.nd sec-he sec-oncept,nalyz-an be arevealLoadIrreversibilityMultidimensional modeling

energy analysis. Various rates and the cumulative exergy components are identied separately for twoengine cases at various loads. The comparison of the results show that, as load engine increases from25% to 100% full load (in 25% increments), the exergy efciency in air injection engine decreases by5.69%, 10.5%, 10.9%, and 10.8% in comparison to baseline engine.

2015 Elsevier Ltd. All rights reserved.

1. Introduction

Nowadays, DI diesel engines are being used more frequently

the other method, the amount of Soot and NOx reduced signi-cantly by adopting air-cell inside piston body [912].

In order to improve engine performance and emissions forma-Air injectionExergy carried out using an in-ho The accumulative burn fuel exergy inc The irreversibility increases by 12.8%, 1 The exergy efciency decreases by 5.69

a r t i c l e i n f o

Article history:Received 31 May 2014Received in revised form 7 February 2015Accepted 12 March 2015Available online 2 April 2015

Keywords:Air-cell.54%, and 7.99%.y 10%, 7.8%, 7.2%, and 8.3%.3.4% and 13.7%.%, 10.9%, and 10.8%.

a b s t r a c t

Research studies indicate that the Soot and NOx emissions in natural aspirated DI diesel engines, can bereduced through applying an air jet. In order to achieve this aim, an air-cell can be designed inside thepiston body by maintaining the performance parameters. The diameter of the air cell is 35 mm and itsheight is 1.2 mm and the diameter of the throats is 1 mm. At the present work, however, exergy analysesare carried out for an MT4.244 engine, which is modeled with an air-cell. Energy analyses and numericalcombustion have been performed for compression ratios of 25%, 50%, 75% and 100% full load. A three-di-mensional CFD code is employed for this purpose in a closed cycle. The numerical results of cylinder pres-sure are compared with the measured experimental data and show a good agreement. Exergy analysis isExergy analysis of air injection at varioudirect injection diesel engine using mult

S. Jafarmadar , M. MansouryMechanical Engineering Department, University of Urmia, Urmia, West Azerbaijan 5756

journal homepage: wwwoads in a natural aspiratedmensional model

311, Iran

le at ScienceDirect

l

l sevier .com/locate / fuel

ry / Fscheme on exergy terms in an IDI diesel engine by three-dimen-sional modeling. The results show that the results show that thevalues of work exergy and exergy efciency decrease when thedwell duration is changed from 5CA to 30CA. Also, there is asharp change in the exergy parameters when the dwell timereaches 25CA. Jafarmadar and Javani [22] investigated an HCCIengine, fuelled with the mixture of dimethyl ether (DME) andnatural gas (NG) in terms of exergy. They showed that when theexcess air ratios of DME increases at constant air ratio of NG,exergy efciency increases by 30.2% while irreversibility decreasesby 15.4%. Moreover, increase in initial temperature brings aboutthe irreversibility reduction and increases the heat loss exergy.Amjad et al. [23] used a single-zone model to perform a numericalavailability analysis for the combustion of n-heptane and naturalgas blends in Homogenous Charge Compression Ignition (HCCI)engines. Hosseinzadeh et al. [24] carried out a numerical studyby comparing the thermal, radical and chemical effects of EGRgases using a single-zone model to analyze availability in dual-fuel

Nomenclature

E internal energy (J)G Gibbs function (J)Ex exergy (J)S entropy (J/K)T temperature (K)kk number of speciesI irreversibility (J/K)y mass fraction of species

Greek lettersl chemical potential (J/kg)h crank angle (degree)z number of carbon atom

AbbreviationsBTDC before top dead centerATDC after top dead centerEVO exhaust valve opening (degree)

124 S. Jafarmadar, M. Mansouengines operated at 50% loads. Turan [25] studied exergeticinu-ence of some design parameters on the small turbojet engine forunmanned air vehicle applications. Jafarmadar [26] studied theeffect of EGR mass fraction on exergy terms in an indirect injectiondiesel engine. He showed that, as EGR mass fraction increases from0% to 30% (in 10% increments), exergy efciency decreases from31.74% to 25.38%. Also, the cumulative irreversibility related tothe combustion chamber decreases from 29.8% of the injected fuelexergy to 25.5%. Jafarmadar [27] carried out a numerical exergyanalysis in pre-chamber and main chamber of an indirect injectiondiesel engine by three-dimensional model. Also in anotherresearch, Jafarmadar [28] carried out a numerical analysis aboutthe effect of engine load on the exergy terms of an (indirect injec-tion) IDI diesel engine by three-dimensional modeling. Jafarmadaret al. [29] carried out an exergy analysis at various loads in an IDIlow heat rejection diesel engine by three-dimensional modeling.They showed that the best operational load is 75% full load fromsecond law viewpoint.

The study of the relevant literature shows that no attempt hasbeen done up to now in order to three dimensionally study theeffects of air injection at various loads on the exergy terms in DInaturally aspirated diesel engine. In the present numerical work,the effect of creating an air jet by embedding an air-cell within pis-ton on combustion parameters in a DI diesel engine has been stud-ied at various loads from the second law perspective.2. Initial and boundary conditions

Inlet temperature at 300 K, initial pressure at 1.85 bar, andengine speed at 2000 rpm are set to be. In-cylinder swirl for bothbase and modied conditions are considered to be uniform, theamount of exhaust gas recirculation is assumed to be zero.

Regarding that the analysis is done on the closing cycle, fromintake valve closure (140 BTDC) to exhaust valve opening (130ATDC), so the domain of the calculation include the space of cylin-der, which is divided into head, liner and piston bowl. Simulationof modied engine condition follows the above-mentioned pro-cess. In this condition, an air cell and four throats are added tothe initial geometry. The diameter of the air cell is 35 mm and itsheight is 1.2 mm. The diameter of the throats is 1 mm. Fig. 1(a)and (b) demonstrates the simulated engines in base and modiedconditions, respectively. In order to investigate grid dependency,combustion chamber pressure at 100% load condition for 22,504cells and 56,321 cells is presented in Fig. 1(c). As can be seen in

CA crank angle (degree)EBU eddy break upID ignition delay(crank angle)

Subscriptch relating to chemical exergytm relating to thermo-mechanical exergyf relating to fuelw associated with work transferQ associated with heat transfer0 dead state, or environment statepr relating to combustion productsox relating to oxidantsfuel relating to fuel

Superscript0 restricted dead state

uel 154 (2015) 123131the gure, increasing or decreasing the number of the cells hasno effect on the results. Boundary temperatures in the combustionchamber are as follow:

Head temperature: 510 K. Piston temperature: 540 K. Cylindertemperature: 480 K.

3. Energy analysis

In the present work, AVL Fire U. 8.3 software is used for numeri-cal simulation of combustion, exhaust emissions, and precise mod-eling of spraying fuel jet and injecting droplets [30]. Theinvestigated engine is a direct injection diesel engine MT. 4.244made by Motor Sazan Iran company and its specications are givenin Table 1. In order to explore the effects of air jet, an air cell isannexed to the main combustion chamber. It should be mentionedthat compression ratio in both base and modied engines wereequal. For the 3D simulation, rstly engine cylinder is modeledby Solid work software. Considering the strategy applied in AVLFire software for creating meshes, there is a need to create a sur-face mesh for the model. Thus, the mentioned mesh is created byfame hybrid assistant tool in AVL Fire software while the pistonis located in top dead center. Next, complicated 3D simulation ofengine and creating moving mesh is carried out by means of fameengine plus tool in AVL Fire. The modeling of the auto ignition forhydrocarbon fuel is carried out by Shell auto-ignition model. The

ry / FS. Jafarmadar, M. MansouEddy Break-up model (EBU) based on the turbulent mixing is usedfor modeling of the combustion process.

During the pre-mixed combustion, due to insufcient air insidethe main combustion chamber in modied situation, heat releaserate and combustion pressure for base condition is more than thatfor modied engine. At diffusion combustion stage, owing to theentrance of oxygen from air cell into the combustion chamber dur-ing the course of expansion, the rate of available oxygen at thisstage increases; combustion occurs more intensely during this per-iod for modied condition than that for base engine [11].

4. Exergy analysis

The exergy of a system is the maximum amount of work thatcan be gain from that system when it reaches mechanical, thermal

Fig. 1. Computational geometries for (a) baseline engine, (b) modied

Table 1Specications of MT4.244DI diesel engine.

Number of cylinders 4-in line, verticalNumber of intake valves 1 per cylinderBore stroke (mm) 100 127Cubic capacity 3.99 lCompression ratio 17.5:1Max power 82 bhp @ 2000 rpmMax toque 360 N m @ 1300 rpmCombustion system Direct injectionRotation Clockwise, viewed from frontFuel injection DPA pumpCooling Water cooled with oil coolerDuration of injection (deg) 20Number of nozzle orice diameter (mm) 5 0.276Displacement (lit) 3.99Rate of fuel injected (kg/hr) 15.22Combustion chamber Reentrantuel 154 (2015) 123131 125and chemical equilibrium with its atmosphere. This state of equi-librium is dened as the dead state of the system and it is depen-dent on the pressure, temperature and composition of theatmosphere. According to [3133], the total exergy of a system(i.e., thermo-mechanical plus chemical exergies) is equal to:

Ex Exch Extm E P0V T0SXkki1l0i mi 1

where l0i is the chemical potential of species i at the true dead state,and mi is the mass of species i.

The equation of exergy balance for the inside of the DIengine chamber, on crank angle basis, is expressed as follows[35]:

dExdh

dExwdh

dExqdh

dIdh

dExfdh

2

Exw denotes the work exergy done by the system and it isdened as:

dExwdh

P P0dVdh 3

Also, Exq represents the exergy associated with heattransfer across the chamber boundary. Its variation with crankangle is:

dExqdh

1 T0T

dQdh

4

I is the destruction exergy associated with the combustion pro-cess and it can be dened as:

dIdh

T0T

Xkki1li

dmidh

5

engine and (c) grid dependency based on the in-cylinder pressure.

where index i includes all the reactants and products. For perfectgases, li gi.

The exergy of liquid hydrocarbon fuels (CzHy), which are used incompression ignition engines, is approximated by [34]:

afuel LHV 1:04224 0:011925 yz 0:042

z

;

dExfueldh

afuel dmfueldh6

The exergy efciency can be dened as the ratio of indicatedwork over total input chemical exergy. For the closed part of thecycle in an engine, the exergy efciency is dened as:

gII WnetExfuel

7

5. Results and discussion

Calculations are carried out on an MT. 4.244 direct injection die-sel engine at 25% load, 50% load, 74% load, and 100% load. Fig. 2depicts the comparisons of in-cylinder pressure in the base engineby experimental results. It is seen that there is a good agreementbetween the obtained and experimental results. It should be men-tioned that the peak pressure discrepancy between the computa-tional and experimental models is less than 4%.

Fig. 3 shows the comparisons of in-cylinder average tempera-ture for both base and air injection engines at four working modesof the engines. By decreasing the pressure inside the main chamberat expansion stroke, the reserved air in the air cell injects into themain chamber and causes better combustion of the remaining fuel.By creating air jet, because of increasing of combustion rate at nal

126 S. Jafarmadar, M. Mansoury / Fuel 154 (2015) 123131Fig. 2. Comparison of predicted and measured engine in-cylinder pressure for the base en2000 rpm.gine at (a) 100% load and (b) 75% load, (c) 50% load and (d) 25% load in engine speed

S. Jafarmadar, M. Mansoury / Fcombustion stage, the exhaust temperature from the combustionchamber increases in all four working modes of the engines. Thisphenomenon is observable in this Figure. Increases in the exhausttemperature are as follows; 4.2% at 25% load condition, 6.1% at 50%load, 7% at 75% load, and 7.4% at 100% load. Also, the value of peaktemperature in air injection case is higher than of baseline case at25% load due to more improving of combustion process in low

Fig. 3. The variation of temperature in cylinder with crank angle position forbaseline and air injection engines at various loads and engine speed 2000 rpm.pressure injection. Therefore, the effect of air injection is con-siderable at lower loads due to increasing of temperature andimproving of combustion process in expansion stroke.

Fig. 4. The variation of rate of work exergy with crank angle position for baselineand air injection engines at various loads and engine speed 2000 rpm.In Figs. 4 and 5 are shown the development of both rate andcumulative work exergies in cylinder during for both base andmodied engines at four working modes of the engines. The cumu-lative terms are dened after integration of the respective rateterms over the crank angle engine. At the angles of after start ofcombustion in various load operations, the rate of work exergy atbaseline engine increases more than modied engine and thisincrease is considerable in higher loads due to the lack of sufcientoxygen inside the main chamber. As shown in Fig. 3, the pressure

Fig. 5. The variation of accumulative work exergy with crank angle position forbaseline and air injection engines at various loads and engine speed 2000 rpm.

uel 154 (2015) 123131 127and temperature gradients in cylinder at baseline case are higherthan modied case, consequently, higher rate of work exergy canbe seen at baseline case. By decreasing the pressure inside themain chamber at expansion stroke, the reserved air in the air-cellinjects into the main chamber and causes better combustion ofthe remaining fuel. Therefore, in expansion stroke the rate of workexergies are the same for two cases. The accumulative work exer-gies for 25%, 50%, 75% and full load operations are 267, 614, 924,and 1200 J for baseline engine and for modied case are 277,592, 883, and 1160 J, respectively. It can be seen that when theload increases from 50% to full load, accumulative work exergyfor modied engine decreases by 3.6%, 4.4%, 3.3%, while in 25% loadincreases by 3.7% in comparison to baseline engine.

Figs. 6 and 7 respectively show the trends of heat loss exergyrate and cumulative heat loss exergy in the chamber for two casesat various loads during the engines closed cycle. At crank anglesbeyond the start of combustion, the rates of heat loss exergy forair injection engine is higher than that of the baseline engine,because during the air injection operation, the combustion processimproves at expansion stroke due to air injection and higher oxy-gen availability in the chamber. Also in this case, the heat loss ofengine walls increases due to high surface of heat transfer. It isclear from Fig. 6 that when the air cell is created in the combustionchamber, there are increases in heat loss exergy rate peak and alsothe rate in expansion stroke in comparison to baseline case. As isshown in Fig. 7, the accumulative heat losses exergies for 25%,50%, 75% and full load operations are 54, 85.2, 126, and 172 J forbaseline engine and for modied case are 54.1, 89.9, 133, and187 J, respectively. These values are 7.2%, 5.7%, 5.7%, and 5.9% forbaseline engine and for modied case are 6.6%, 5.6%, 5.6% and

Fig. 8. The variation of the rate of burn fuel exergy with crank angle position forbaseline and air injection engines at various loads and engine speed 2000 rpm.

128 S. Jafarmadar, M. Mansoury / F5.9% of fuel injected exergy, respectively. It is clear that the per-centage of accumulative heat loss exergy in air injection enginedecreases due to complete combustion in expansion stroke andhigher burn fuel exergy. The value for base line engine is conrmed

Fig. 6. The variation of the rate of heat loss exergy in chamber with crank angleposition for baseline and air injection engines at various loads and engine speed2000 rpm.by the work of Primus RJ, Flynn PF [34] considering heat lossexergy in the diesel engines at higher engine speed. They showedthat the amount of heat loss exergy in full load operation andengine speed 1500 rpm is 13.98%. Lower this value at the presentstudy is due to higher engine speed and less time for heat transfer.

Figs. 8 and 9 respectively show the variations of rate of burnedfuel and cumulative burned fuel exergies with crank angle position

Fig. 7. The variation of the accumulative heat loss exergy in chamber with crankangle position for baseline and air injection engines at various loads and enginespeed 2000 rpm.uel 154 (2015) 123131at four working modes of the engines. The process of combustionin diesel engines includes the stages of ignition delay, pre-mixedor rapid combustion, diffusion combustion, and late combustion.Some factors effective in ignition delay are fuel type, oxygen avail-ability, temperature and combustion chamber pressure. At pre-mixed stage, the injected fuel during the delayed period burns ata high rate. Diffusion combustion is associated with the end ofinjection period, and injection stops at late combustion stage whilethe fuel is still being mixed inside the chamber by the gas move-ment; at this stage the rate of combustion basically depends onoxygen availability and the phenomenon of diffusion. At 25% loadand 50% load, one can observe that ignition delay period for modi-ed condition is 1 degree less than those for base condition due tolow oxygen availability. The other reason for this phenomenon isthat there are higher temperature and pressure in the modied

Fig. 9. The variation of accumulative burn fuel exergy with crank angle position forbaseline and air injection engines at various loads and engine speed 2000 rpm.

ry / FS. Jafarmadar, M. Mansoucondition during the ignition delay period. As can be seen in Fig. 8,at the stage of rapid combustion at 25% load and 50% load formodied condition, the rate of burn fuel exergy is higher thanthose for base engine and this is because of providing optimal con-ditions at the period of ignition delay (higher temperature andpressure). During the diffusion combustion, due to insufcient airinside the main combustion chamber in modied situation, burnfuel exergy rate for base condition is more than that for modiedengine. At late combustion stage, owing to the entrance of oxygenfrom air cell into the combustion chamber during the course ofexpansion after 25 ATDC, the rate of available oxygen at this stageincreases; combustion occurs more intensely during this period formodied condition than that for base engine. At 75% load and 100%load, because of high pressure and temperature of combustion

Fig. 10. The variation of thermo mechanical exergy with crank angle position forbaseline and air injection engines at various loads and engine speed 2000 rpm.

Fig. 11. The variation of chemical exergy with crank angle position for baseline andair injection engines at various loads and engine speed 2000 rpm.uel 154 (2015) 123131 129chamber at ignition delay period, burn fuel exergy rate at pre-mixed stage in base condition is higher than that in modiedengine. The behavior of burn fuel exergy rate curve at diffusioncombustion stage is similar to those at 25% load and 50% load.Also at late combustion stage due to recirculation of air into themain combustion chamber, more intensied turbulence occurs inmodied condition than in base engine. The effect of reserved airjet on main chamber in modied engine is seen as uctuations inburn fuel exergy rate at late combustion period. As is shown inFig. 9, the accumulative burn fuel exergies for 25%, 50%, 75% and

Fig. 12. The variation of total exergy with crank angle position for baseline and airinjection engines at various loads and engine speed 2000 rpm.

Fig. 13. The variation of accumulative irreversibility with crank angle position forbaseline and air injection engines at various loads and engine speed 2000 rpm.

full load operations are 747.4, 1500.9, 2227.5, and 2926.3 J forbaseline engine and for modied case are 822.2, 1617.6, 2388.1,and 3169.9 J, respectively. It is clear that when the load increasesfrom 25% to 100%, the percentage of accumulative burn fuel exergyin air injection engine increases by 10%, 7.8%, 7.2%, and 8.3% due toair injection and complete combustion in expansion stroke.

Figs. 1012 show the changes of thermo-mechanical, chemicaland total exergies in the cylinder with crank angle positions fortwo cases at different loads, respectively. In the compressionstroke, and before of combustion, the thermo-mechanical exergyin the chamber increases due to the work produced by the pistonand increase of the initial temperature associated compressionstroke. With the start of fuel injection, chemical exergy increasesdue to increasing of fuel mass fraction and then decrease in thecombustion period due to the burning of the fuel mixtures. Alsowith the start of the combustion process, the thermo-mechanicalexergy in the chamber increases due to the rise of temperature,pressure and the concentration of complete combustion products.It is clear that the increase of chemical and thermo-mechanicalexergies with load operation are considerable at higher loadsbecause of higher fuel injection higher pressure and temperaturein the cylinder. At the end of the combustion duration, the amountof chemical exergy reaches to the minimum value because of thecomplete combustion, while the thermo-mechanical exergy dimin-ishes due to the decrease of gas temperature during the expansionstroke. As Fig. 12 illustrates, when the load increases from 25% to100% full load in air injection case, the exhaust loss total exergiesincreases by 17.8%, 22%, 22.8% and 22.9% in comparison to baselineengine. This occurs from higher pressure and temperature at theexhaust valve opening time in the air injection case (as shown inFig. 3).

130 S. Jafarmadar, M. Mansoury / FFig. 14. The variation of (a) exergy efciency and (b) energy efciency with loadengine.The combustion process makes the highest contribution to thetotal in-cylinder irreversibility in a diesel engine, which accordingto the research by Primus and Flynn [35], is more than 90%. Fig. 13illustrate the trend irreversibility due to in-cylinder combustionduring an engines closed cycle at two cases in various loads. Atbaseline engine case, with more oxygen availability, which resultsin very rapid burning rates (Fig. 9), combustion continue withhigher rate of temperature variation. Therefore, the rate ofirreversibility increases more at baseline case than at air injectioncase particularly in higher loads. It is clear from Fig. 13 that whenair injection is used in expansion stroke and the load increasesfrom 25% to 100% load, the values of cumulative irreversibilityincrease by 12.8%, 14.7%, 13.4%, and 13.7% due to the improvingof combustion and cumulative irreversibility increases in compar-ison to baseline case.

The variation in the exergy and energy efciencies with loadengine is shown in Fig. 14 for baseline and air-cell cases.According to this gure, the values of the exergy and energyefciencies diminish with load engine at both two cases. Also, itis evident from the Figure; air injection in each load will result ina decrease of both rst and second-law efciencies which is dueto the increase in irreversibility, heat loss, and exhaust losses.

6. Conclusions

In the present work, a three-dimensionally exergy analysis wasperformed on an MT4.244 engine under air-injection at variousloads. The calculated pressures for the base engine are comparedwith the corresponding experimental data at various loads, andshow very good agreement. Such correlations between the experi-mental and computed results make the model reliable for the pre-diction of exergy terms in air-injection case. Various exergy termsincluding the fuel, heat loss, irreversibility, work, exhaust loss,chemical and thermo-mechanical exergies are presented and com-pared for baseline and air injection cases. The results of the study,when the load increases from 25% to 100% in 25% steps, are asfollows:

1. Peak temperatures in cylinder at air injection engine increaseby 3.22% in 25% load and in others loads decrease by 3.5%,2.6%, and 2.8% in comparison to base engine.

2. Exhaust temperature in cylinder at air injection engine increaseby 6.5%, 6.5%, 7.54%, and 7.99% in various load operations,respectively.

3. The accumulative burn fuel exergy in air injection engineincreases by 10%, 7.8%, 7.2%, and 8.3% in various load opera-tions, respectively.

4. The cumulative heat loss exergy increases in air injectionengine by 0.2%, 5.5%, 5.56%, and 8.72% in various load opera-tions, respectively.

5. Exhaust chemical exergy at air injection engine decreases by59% in 25% load and increases by 10%, 12.7%, and 23.5% inothers load operations, respectively.

6. Exhaust thermo-mechanical exergy at air injection engineincreases by 23.8%, 22.2%, 23.1% and 23.9% in various loadoperations, respectively.

7. The irreversibility in air injection case increases by 12.8%, 14.7%,13.4% and 13.7% in various load operations, respectively.

8. The exergy efciency in air injection engine decreases by 5.69%,10.5%, 10.9%, and 10.8% in various load operations, respectively.

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Exergy analysis of air injection at various loads in a natural aspirated direct injection diesel engine using multidimensional model1 Introduction2 Initial and boundary conditions3 Energy analysis4 Exergy analysis5 Results and discussion6 ConclusionsReferences