MODELING AND SIMULATION OF COMPRESSION IGNITION ENGINES

This article was downloaded by: [University of Auckland Library]On: 05 November 2014, At: 15:11Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

Fuel Science and Technology InternationalPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/lpet19

MODELING AND SIMULATION OF COMPRESSION IGNITIONENGINESYousef S.H. Najjar a & Abdullah M. Alturki aa Mechanical Engineering Department(Thermal) , King Abdulaziz University , Jeddah , S.APublished online: 25 Apr 2007.

To cite this article: Yousef S.H. Najjar & Abdullah M. Alturki (1996) MODELING AND SIMULATION OF COMPRESSION IGNITIONENGINES, Fuel Science and Technology International, 14:8, 1019-1035, DOI: 10.1080/08843759608947626

To link to this article: http://dx.doi.org/10.1080/08843759608947626

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in thepublications on our platform. However, Taylor & Francis, our agents, and our licensors make no representationsor warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Anyopinions and views expressed in this publication are the opinions and views of the authors, and are not theviews of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should beindependently verified with primary sources of information. Taylor and Francis shall not be liable for any losses,actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoevercaused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/loi/lpet19

http://www.tandfonline.com/action/showCitFormats?doi=10.1080/08843759608947626

http://dx.doi.org/10.1080/08843759608947626

http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/page/terms-and-conditions

FUEL SCIENCE & TECHNOLOGY INT'L., 14(8), 1019-1035 (1996)

MODELING AND SIMULATION OF COMPRESSION IGNITION

ENGINES

rouser S.H. Najjar and Abdullah M. Alturki

Mechanical Engineering Department (Thermal)

King Abdulaziz University-Jeddah -SA

ABSTRACT

Modeling of a compression ignition engine was carried out coveringlosses

emanent from imperfect construction of real engines such as progressive

combustion, valve timing, and heat transfer. Furthermore, friction was

included to obtain brake performance. Simulation of engine performance

was tackled by varying engine speed, compression ratio and injection

timing over wide range. The results were compared with those obtained

from the experiemntal facility.

Predictions by the model compare favourably with experiment within

(n~ and <j.n for power and stc respectively. The losses considered in

1019

Copyright C 1996 by Marcel Dekker, Inc.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

1020 NAJJAR AND ALTURKI

this work amount to about 30% of the fuel energy input at the design

point.

INTRODUCTION

This paper is a continuation for the previous one on modeling of spark

ignition engine [II. Hence, the detailed background on engine losses in

the introduction; and the nomenclature are almost similar for the two

papers. Further consideration of losses could be found in [2-61. As far as

the experimental facility is concerned, the same test facility and

procedure, previously mentioned, have been used with the same engine

converted to a compression ignition engine after some modifications such

as using fuel injection system instead of the carburetor. The fuel used is

light diesel Which has the properties shown in Table 1.

MODELING AND SIMULATION

The ideal model used in this work is based on that of campen [7].

However, for the purpose of this work some modifications were made

namely; fuel, compression ratio, injection timing, air mass flow rate and

heat of combustion.

In this ideal gas model, variation of thermodynamic properties with

temperature is assmed for both reactants and products. Approximations

are assumed to fit limited equilibrium products. Furthermore,

compression and expansion processes are isentropic as snown in fig. 1.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

COMPRESSION IGNITION ENGINES

Table 1. Properties of diesel fuel

1021

Property Gasoline

Formula CH 1.75

Relative molecular mass 220

Carbon/hydrogen mass ratio 6.857

Carbon, %by wt 87.3

Hydrogen, %by wt 12.7

Density, kg/ I 0.850

Netheat of combustion, II.]/kg. 42,517

Stoichiometric A/F mass ratio 14-53

Formula C16 H28

Distillation

Initial boiling point, 'C

10% recovery by Vol., 'C

50% recovery by Vol., 'C

90% recovery by vet, 'C

162

208

285

350

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

1022

VTDe

VCYI

NAJJAR AND ALTURKI

41

VBoe

Fig. 1 Fuel _ air cycle of C. 1. engin e

Then, the compression work is

WCOMP = (NA + NX) CVR (T2-T1)

where NA and NX are the moles of air and residual gas , CVR is the

constant volume heat capacity of the mixture, while T I and T2 are the

temperatures at the start and end of the compression stroke.

In the following, losses due to imperfect construction of the engine

namely progressive combustion, valve timing and heat transfer are

considered in addition to friction. Hence the fuel-air cycle is converted to

brake performance.

Progressive Combustion

If mass fraction DN. of the fuel burns while the piston moves through a

volume change amounting to tN, the resulting change in pressure, is

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


DV VTOCDP = - P K- + (P3 -P2)- DN

V V

where k = CplCv

1023

(2 )

P2 = pressure at TDC at end of the compression stroke.

P3 = the pressure that would be reached if all the fuel burned

instantaneously at TDC

The volume V3can be found by

V3 = VTOC [ I + P_3;.,..-_P_2 ]K P2

(3)

Now examine the time rate of burning, represented by the ratio DN/dt.

Writing the equation in the following form:

DN = I F(Z) DZdt V3 - VIDe dt

where

Z= crank angle at start of combustion

DZ = crank angle incrementstep in combustion process.

This equation can be used when ZIl = 0.0, but when ZIb: 0.0, then

DN = F(Z-ZII) *D2I(V 3-VTDC)dt

where

ZI I = crank angle at start of injection before TOe, radians.

The combustion processmust be followed in stepwise fashion:

DV = F(Z) DZ

(4)

(6)

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

Table 2. Range ot operating variables Cor the c.1. Engine

CR 14.00 16.00 18.00 20.00

21ID 000 10.00 20.0 30.00

N,rpm 1250 1500 2000 2250

Table 3. Experimental data Cor the single cylinder C.1. engine

engine speedlrpm) 1250 1500 2000 2250

C.IE. power (kW) 3.30 4.30 5.90 6.20

SFC(g/kW h) 313.0 309.0 3250 355.0

16.00

12.00

V 8.000<o

CL

4.00

0.00100000 1500.00 2000.00

Engine speed. rpm2500.00

Fig.2: Variation of power with engine speedfor different modifications

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

COMPRESSION IGNITION ENGINES 1025

.---.--------. ideal

experiment

•_____.~~ friction

,---;~.

____...----. heat transfer

--~'----'.---' • valve timing,-'

• .---. progressive

--- cornbustlon

2500.001500.00 2000.00Engine speed. rpm

100.00

50.001000.00

150.00

400.00

300.00

350.00

U 200.001.L

'Jl

s:~

<,250.00C1'

Fig.3: Variation of SFC with engine speedfor different modifications

Where F(Z): the derivative of engine volume, m3, When the burning rate

reaches the maximum allowable value

DN = DNmaxDT

The expansion work is found by

WEXP = L [p + DP l"v + U (T3) - U (T4)2 f p p

(3)

Where the summation applies for the entire combustion process, and T3

is the temperature at the end of combustion [71.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


'=f=====-=i friction----==. experiment

'-_______ idee!-----.---.tc__ progressive

• • * combustion

---,,___ valve timing

"-------.----=::---.==--- heat tronsfer

2500.001500.00 2000.00Engine speed, rpm

20.00

60.00

10.001000.00

L50.00

70.00

~ 30.00~

<l)

s:I-

>u

.~ 40.00

.~

Fig.4: Variation of therm.ol efficiency with enginespeed for different modifications

Table 4. Variation in power, stc and efficiency due to ideal

engine modifications at the design point

(Qin,i =22.521 kW; SFCi = 152.92 g/kWh)

Engine with Power, kW S.F.C. g/kWh 1],%

ideal cycle 12.47 152.92 55.37

p.c 913 20881 4054

'{.t 8.06 236.52 35.79

h.t 779 244.82 3459

friction 5.35 330 2376

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


1400 -

--' ideal

12.00 »->:.i->:

10.00progressive

:: -' combustion.:< --'.-----' -

verve timing

L 8.00 -------.::::::: '::::::::====: heat transfer<V~ :::::::---.0CL

6.00friction--',--'4.00

2.00 -n-rTTlTTTTTTTTrrTTlCTTTTTTTl"TrTTlTTTTTTTTTlrTTlTTTTTl

12.00

1027

Fig.5: Variation of power with compression ratiofor different modifications

Valve Timing and Heat Transfer

Tile procedure is similar to that followed in the spark ignition engine,

because the same engine is used in both modes.

FRICTION

Friction MEP increases as engine size decreases [3.9],

FMEP = CI + 48 (N/lOOO)+ 0.4 S2p

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


friction

heot tr onster

votve liming

progressivecombustion'-._------• idee!

:~:_-==='-. ====

400.00

0.00 ~

12.00 14.00 16.00 18.00 20.00 22.00Compression rolio, CR

500.00

10000

uu: 200.00(f)

.c~ 30000<,0'

Fig.6: Variation of specific fuel consumption withcompression ratio for different modifications

where C1 = 144 kPa. Then friction power is calculated from

FMEP VDISP NFRP=----

120

DISCUSSION OF RESULTS

Engine performance has been parametrically studied using experimental

work and modeling. The range of operating conditions is shown in table

2. The design point comprises N=2000 rpm, CR = 18, and fuel injection

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

2.00 IIII1 Iii II III iii l i I II1I1 I Iii i I I' I til i i II I0.00 10.00 20.00 30.00 40.00

Injection timing. (degree)


14.00

idealI12.00 <.10.00 .~:~

~.x: ~.-: 8.00 .~ ~ progressive<ll combustion30

Q.. valve timing

6.00 <. heal transfer

4.00 <.friction

Fig.7: Variation of power with injection timingfor different modifications

timing ZII = 20"BTC. Experimental results obtained by varying N are

shown in table 3. Performance in general, is graphically represented.

Figure 2 shows the variation of power with engine speed N ior diiierent

modifications of the ideal engine namely progressive combustion, valve

timing and heat transfer to get the indicated power ior the real engine.

Friction is then subtracted to produce the brake power which is

compared vvttn the experimental results.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


valve timing

progressivecombustion

ideo!

friction

heat transfer

0.00 II iii 1111'lll III II I Iii., l j I II I II' i 1111111

0.00 10.00 20.00 30.00 40.00Injection liming. (degree)

500.00

400.00

100.00

uu.: 200.00if)

s:

~ 300.00<,en

Fig.8: Variation of specific fuel consumption withinjection timing for different modifications

Figures 3 and 4 show the variation of src and T] with N for similar

modifications as those with power. Table 4 shows the variation in

efficiency along with power and sfc due to these modifications at the

design point.

Figures 5 and 6 show the variation of power and sfc respectively with

compression ratio CR, whereas, figures 7 and a show the variation with

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


1.60

1.40

1.20

~

~ 1.00oa.

00.80z

0.60

0.40

0.20

N

1031

0.00 0.50 1.00 1.50 2.00Non-dimentional variables (N, CR, ZII)

Fig.9: Relative effect of operating variableson power

injection timing ZII. Figures 9 and 10 show the relative effect of the

operating variables namely N, CR and ZII on power and '1 respectively.

The highestenect is seen to be for Nthen ZI I followed by CR.

Figures I I and 12 compare the model predictions with the experimental

results for power and sfc. It is noticed that the percentage deviation

from experiment,at the design point, is about 9.3% in power, and 9.7% in

SFe.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


1.40

1.20

>. 1.00ucQ)

.«W

0.80

0.00 0.50 100 1.50 2.00Non-dimentional voriobles (N, CR, ZII)

Fig,10: Relative effect of operating variableson efficiency

CONCLUSIONS

1- Modeling effort comprised engine losses ernanent from imperfect

construction such as progressive combustion, valve timing and heat

transfer. By adding engine friction, brake performance results.

2- Engine performance was simulated by varying, widely, engine

speed N, compression ratio CR, and injection timing21 I.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


7.00

600

~ 5.00

LQ)

~e 4.00

300

/ model

2500.001500.00 2000.00Engine speed. rpm

2.00 --hrr-rrr-rTTTT..-r-.--r-,--,-,-,rrrrr-rTTTT"--"1000.00

Fig.l1: Comparison of model with experimentversus engine speed

3- A modified single cylinder compression ignition engine was used as

experimental facility with the potential of varying the above-

mentioned variables.

4- The model compares favourably with experiment within 9.3% and

9.7% for power and SFC respectively.

5- The relative effect of the losses on performance is generally in this

sequence: progressive combustion, friction, valve timing and heat

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


360.00

350.00

340.00

L3:<,330.000'

U 320.001.L

(f)

310.00

300.00

290.001000.00

-:.i->

'----.

1500.00 2000.00Engine speed, rpm

• experiment

model

2500.00

Fig.12: Comparison of SFC from model withexperiment versus engine speed

transfer. These losses amount to about 30% of the fuel energy

input at the design point.

ACKNOWLEDGEMENTS

Assistance received from Mr. O. Bashir and Mr. H. Abu Kayyas is

gratefully acknowledged. Thanks are extended to Dr. M. Zaamout for

producing most of the graphs.

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014


REFERENCES

1- Najjar Y.SH. and Alturl<i, A.M., "Mo<Ieling and simulation or spark

ignition engines", submitted for publication.

2- Ferguson, CR. "Internal Combustion Engines", john Wiley, New

Yorl<, 1986.

3- Taylor, C.F., "Internal Combustion Engines in Theory and Practice",

The MIT Press,Cambridge, 1966.

4- Lichty, L.C., "Combustion Engine Processes·, McGraw-Hill, New Yorl<,

1967.

5- Mathur, M.L. and Sharma, R.P., "A course in Internal Combustion

Engines", DhanpatRai, Delhi, 1990.

6- Ballaney, P.L., "Internal Combustion Engine", Khanna Publishers,

Delhi, 1980.

7- Campell, A.s., ""Thermodynamic Analysis of Combustion Engines",

John Whiley & Sons, New Yor1<., 1979.

8- Millington, B.W., and Hartles, ER., "Friction losses in diesel engines",

Paper 680590, SAE Trans., Vol. 77, 1968.

9- Heywood. J.B., "Internal Combustion Engine Fundamentals",

McGraw Hill, NewYorl<, 1988.

RECEIVED: June IS, 1995

ACCEPTED: September 23, 1995

Dow

nloa

ded

by [

Uni

vers

ity o

f A

uckl

and

Lib

rary

] at

15:

11 0

5 N

ovem

ber

2014

Documents

MODELING AND SIMULATION OF COMPRESSION IGNITION ENGINES