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EXERGY ANALYSIS IN INTERNAL COMBUSTION ENGINE USING DIESEL AS FUEL

Presented By : F. Aadil Arshad

Guided By : Dr K. Pitchandi Professor

DEPARTMENT OF MECHANICAL ENGINEERING

SRI VENKATESWARA COLLEGE OF ENGINEERING

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ABSTRACT

• This study represents the exergy analysis in a single cylinder, four stroke diesel engine.

• The engine was run with diesel fuel.• The fuels used in combustion applications has significant

influence on irreversibility generation and hence the exergetic efficiency of the engine.

• This work discusses a method of estimating the availability destructions and exergetic efficiency of combustion for the fuel used.

• Though unsaturated hydrocarbon fuels are associated with lower availability destruction, they result in poor exergetic efficiency as a significant fraction of the fuel availability is lost in the products. .

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OBJECTIVE

The find the irreversibilty generation happening in the engine and to calculate the exergy efficiency of the engine.

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Introduction

• Exergy is defined as the maximum useful work that can be obtained through interaction of the system with its surroundings.

• The exergy of a system in equilibrium with its environment is zero.• Physical exergy is the maximum work obtained by passing the unit

of mass of a substance of the generic state ( T, P ) to the environmental state (To, Po ).

• Chemical exergy is the maximum useful energy which would be attained by passing from the environmental state to the dead state, by means of chemical processes with reactants and products at the environmental temperature and pressure, when the stream composition is not in chemical equilibrium with the environment.

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Make Kirloskar AV 1 model

Type of Engine Vertical,4-Stroke cycle, single acting, High speed , DI, diesel engine

Number of Cylinder One

Speed 1500rpm

Maximum power output 4.4 KW

Bore 87.5mm

Stroke 110mm

Cubic Capacity 0.553 litres

Compression ratio 17.5:1

Type of cooling Air cooled

BMEP @ 1500 rpm 5.42 bar

Specifications of the Engine

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Experimental Setup

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Assumptions

1.The combustion air and exhaust gas are ideal gas mixtures.

2.The potential and kinetic energy effects of the combustion air, exhaust gas and fuel stream are to be ignored.

3.Atmospheric Pressure as 1atm and Temperature as 25 0Celsius were taken.

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Formulae Used1.The specific flow exergy of a fluid stream is given by

e ex = e th + e ch

2.The thermo mechanical exergy is given by

e th = (h – h0) – T0 (s – s0)

3.The chemical exergy of the liquid fuel is given by

e ch = [ 1.0401 + .1728 h/c + .0432 o/c + .2169 s/c + ( 1 – 2.0628 h/c )] ( L.H.V)

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4. Chemical exergy of the exhaust gas is given by

e ch = R T0 ∑ ai ln ( yi/y)

5. Exhaust gas losses are calculated by

Q ex = ∑ ni Cpi (Tex – T0) 6. Cooling air exergy is given by

E ca = (1 – T0 / Tca) Qloss

7. Exergetic efficiency is given by

Ψ = Exout / Exin

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8. Exhaust Exergy Rate

Ex exhaust = Ʃmi [ Ʃtm + Ʃch ]

9. Heat carried away by the exhaust gases

Qg = mg Cpg (Tex – T0)

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Diesel (C12H23)

C12H23 + (12+23/4) O2 + 3.76 (12+23/4) N2 → 12CO2

+ 11.5H2O + 66.74 N2

C12H23 + 17.75 O2 + 66.74 N2 → 12CO2 +11.5 H2O +

66.74 N2 Mass of Fuel = (12 * 12) + (23 * 1.008) = 0.002786 Kg/min

Mass of Air = (17.75 * 32) + (66.74 * 28)

= 0.0406 Kg/min

MODEL CALCULATION

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1. Net Exergy Work Rate

T = 450KExin = ṁ fuel Ʃ fuel

ṁ fuel = 0.002786 Kg/minƩ fuel = Hu φ Hu = L.H.V = 44500 kJ/kg

Chemical exergy factor

φ = [ 1.0401 + 0.1728 h/c + 0.0432 o/c + 0.2169 a/c ( 1 - 2.0628 h/c ) ] = 1.0401 + 0.1728 ( 13.86/86.14) + 0.0432 ( 0 ) + 0 + 0 = 1.0679 h → mass fractions of hydrogen in the fuelc → mass fractions of carbon in the fuelo → mass fractions of oxygen in the fuela → mass fractions of sulphur in the fuel

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Ʃ fuel = 44500 * 1.0679 = 45696.66 kJ/kgExin = 0.002786 * 45696.66 = 132.39 kJ/kg

2. Specific Thermomechanical Exergy of Exhaust Gases

Ʃtm = (h – h0) – T0 (s – s0)

Exhaust gases = CO2 , CO , O2

CO2

Ʃtm = ( 15483 - 9364 ) - 298 ( 230.194 - 213.685 )

= 1199.31 kJ/kmol

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CO

Ʃtm = ( 13116 - 8669 ) - 298 ( 209.5963 - 197.543 )

= 856.10 kJ/kmol

O2

Ʃtm = ( 13228 - 8682 ) - 298 ( 217.342 - 205.033 )

= 877.918 kJ/kmol

Thermomechincal Exergy of Exhaust Gases = 977.77 kJ/kmol

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3. Chemical Exergy of Exhaust Gases

e ch = R T0 ∑ ai ln ( yi/y)

ai = 1.1 + 17.88 + .06 = 19.04

ech = 8.314 * 298 * 19.04 ( ln ( 1.1 / 0.03 ) +

ln ( 17.88 / 20.95 ) + ln ( 0.06 / 0.02 ) )

= 733784.46 kJ/kmol

4. The specific flow exergy of a fluid stream

e ex = e th + e ch

= 977.77 + 733784.46 = 734762.23 kJ/kmol

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5. Heat Carried Away By Exhaust Gases

Qg = mg Cpg (Tex – To)

= 0.04 * 1.005 ( 450 - 298 )

= 6.110 kJ/min

6. Net Work Output Thermal Efficiency = W/Qf

0.2848 = W/m*L.H.V

W = 0.2848 * .002786 * 44500

W = 35.31 kJ/min

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7. Exhaust Loss From The Engine

Q ex = ∑ ni Cpi (Tex – T0)

= 3 ( 450 - 298 ) [ 0.978 + 1.054 + 0.956 ]

= 1363.440 kJ/kg

8. Exergy Lost Rate Through Heat

E ca = (1 – T0 / Tca) Qloss

= [ 1 - (298 / 343)] * 1363.440

= 178.877 kJ/kg

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9. Exhaust Exergy Rate Ex exhaust = Ʃmi [ Ʃtm + Ʃch ]

= 0.02169 [ 877.918 + 733784.46 ]

= 15.93 kJ/min

10. Exergetic Efficiency Ψ = Exout / Exin

= 35.31 / 132.39

= 26.7 %

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Diesel Pressure = 240 bar , Injection Timing = 24 deg

0 25 50 75 1000

10

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30

40

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Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%

)

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Pressure = 200 bar , Injection Timing = 19 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%

)

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Pressure = 220 bar , Injection Timing = 19 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%

)

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Pressure = 240 bar , Injection Timing = 19 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%

)

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Pressure = 220 bar , Injection Timing = 23 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%)

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Pressure = 240 bar , Injection Timing = 23 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%

)

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Pressure = 200 bar , Injection Timing = 27 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%)

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Pressure = 240 bar , Injection Timing = 27 deg

0 25 50 75 1000

10

20

30

40

50

Exergy Efficiency

LOAD (%)

EF

FIC

IEN

CY

(%)

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Conclusions

• Diesel being a volatile fuel , the exergies i.e, work potential of the fuel have been found to be good when incoming to the system as well as from the exhaust gases.

• These experiments show that, different exergy efficiencies were produced at different loads by altering the injection pressure and injection timing.

• The variation of the graphs shows that, the exergy efficiencies were maximum at 75 % and 100 % load conditions.

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• The maximum exergy efficiency produced from this engine was 33.14 % and 32.88 %, both of which were obtained at 100 % load conditions.

• Depending upon the requirement, the load, injection pressure and injection timing can be varied to obtain different exergy efficiencies, but the bottomline is, only at full load conditions the exergy efficiency would be maximum.

• By retarding and advancing the injection timing, the exergy efficiency was found to be maximum at full load conditions.

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• By increasing the injection pressure to 240 bars and advancing the injection timing to 270, the exergy efficiency was found to be minimum, even at 100 % load conditions.

• Only when the injection pressure was decreased to 200 and 220 bars and injection timing lowered to 190 and 230 , the exergy efficiency improved.

• These exergies lost were mainly due to mechanical wear, friction, combustion, mixing and throttling

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SCOPE FOR FUTURE WORK 

• The injection pressure and injection timing used for this experiment could be tried upon other fuels like ethanol, methanol and bio-diesel.

• The exergy efficiencies obtained from these fuels could be compared with the exergy efficiencies obtained from diesel fuel.

• The same procedure could be done for different engines, different fuels.

• The experiment could be even done in a different way by changing the compression ratio.

• The readings obtained from these results can be analysed and we will be in better position to analyze the best load conditions, the best injection pressure, injection timing and compression ratio in getting the highest exergy efficiency.

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1. Saleel Ismail, Pramod S. Mehta, 2010 Evaluation of the effects of fuel and combustion - related processes on exergetic efficiency.

2. Samad Jafarmadar, 2012 Three-dimensional modelling and exergy analysis in Combustion Chambers of an indirect injection diesel engine

3. Mustafa Ertunc Tat, 2011 Cetane number effect on the energetic and exergetic efficiency of a diesel engine fuelled with diesel.

4. C. Sayin, M. Hosaz, M. Canakei, I. Kilicaslan Energy and exergy analyses of a gasoline engine DOI : 10.1002/er.1246

References

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5. Muammer Ozkan, Derya Burcu Ozkan, Orkun Ozener, Hasan Yilmaz, 2012 Experimental study on energy and exergy analyses of a diesel engine performed with multiple injection strategies : Effect of pre-injection timing

6. C.D. Rakopoulos, E.G. Giakoumis, 2005 Second-law analyses applied to internal combustion engines operation.

7. R. Saidur, M. Rezaei, W.K. Muzammil, M.H. Hassan, S. Paria, M. Hasanuzzaman , 2012 Technologies to recover exhaust heat from internal combustion engines.

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THANK YOU