2. Fuel-Air Modeling of IC Engine Cycles P M V Subbarao Professor Mechanical Engineering Department Another Step towards Phenomenological Modeling.….

3. A Route to Know the Truth before trying

4. The Important part of Cycle is Executed in CM Mode More realistic representation of Compression???

5. Realization of Available Air : Running Cost Vs Capital Cost

6. Fuel-Air Models for Engine Cycles Fuel-air analysis is more accurate analysis when compared to Air- standard cycle analysis. An accurate representation of constituents of working fluid is considered. More accurate models are used for properties of each constituents. ProcessSI EngineCI Engine IntakeAir+Fuel +Residual gas Air+ Recycles gas + Residual gas CompressionAir+Fuel vapour +Residual gas Air+ Recycles gas + Residual gas ExpansionCombustion products Combustion Products ExhaustCombustion products Combustion Products

7. Fuel – Air Otto Cycle Air+Fuel vapour +Residual gas Compression Process TC Const volume combustion Process Expansion Process Products of Combustin BC Const volume Blow down Process Products of Combustin

8. Fuel –Air Otto Cycle 1—2 Isentropic compression of a mixture of air, fuel vapour and residual gas without change in chemical composition. 2—3 Complete combustion at constant volume, without heat loss, with burned gases in chemical equilibrium. 3—4 Isentropic expansion of the burned gases which remain in chemical equilibrium. 4—5 Ideal adiabatic blow down.

9. Isentropic Compression Process For a infinitesimal compression process: Mass averaged properties for an ideal gas mixture: Use appropriate EoS:

10. Variation of Specific Heat of Ideal Gases GasC0C0 C1C1 C2C2 C3C3 Air1.05-0.3650.85-0.39 Methane1.23.250.75-0.71 CO 2 0.451.67-1.270.39 Steam1.790.1070.586-0.20 O2O2 0.88-0.00010.54-0.33 N2N2 1.11-0.480.96-0.42

11.  cpcp cvcv

12. Properties of Fuels Fuel C0C0 C1C1 C2C2 C3C3 C4C4 Methane-0.2914926.327-10.6101.56560.16573 Propane-1.486774.339-39.0658.05430.01219 Isooctane-0.55313181.62-97.78720.402-0.03095 Gasoline-24.078256.63-201.6864.7500.5808 Diesel-9.1063246.97-143.7432.3290.0518

13. True Phenomenological Model for Isentropic Compression Let the mixture is modeled as:

14. First Order Models for Variable Specific Heats a p = 0.9718 – 1.1 kJ/kg.K b v = 0.685 – 0.823 kJ/kg.K k 1 = 1.326  10 -4 – 3.395  10 -4 kJ/kg.K 2

15. Isentropic Compression model with variable properties For compression from 1 to 2:

16. 2—3 Complete & Adiabatic combustion at constant volume 0 0 Quasi-static view of sudden process:

17. Second law limit on possible extent of reaction Reactants  Products At any instant during the combustion process, a cylinder contains a combination of reactants and products. A reaction seizes when the entropy of an adiabatic reactor reaches its maximum value. The value of maximum entropy will vary with the pressure and temperature of the reaction. A reaction system and parameters of reaction should be designed such that the maximum entropy is obtained when the reaction is almost complete (>98%??).

18. BS-IV : Emission norms for passenger cars ( Petrol) NormsCO( g/km)HC+ NOx)(g/km) 1991Norms14.3-27.12.0(Only HC) 1996 Norms8.68-12.403.00-4.36 1998Norms4.34-6.201.50-2.18 stage 2000 norms 2.720.97 Bharat stage-II2.20.5 Bharat Stage-III2.30.35(combined) Bharat Stage-IV1.00.18(combined)

19. BS IV : Emission Norms for 2/3 Wheelers ( Petrol) NormsCO ( g/km)HC+ NOx (g/km) 1991 norms12-308-12 (only HC) 1996 norms4.53.6 stage 2000 norms 2.0 Bharat stage-II1.61.5 Bharat Stage-III1.0

20. BS IV : Emission norms for Heavy diesel vehicles: 19 NormsCO (g/kwhr) HC (g/kwhr) Nox (g/kwhr) PM (g/kwhr) 1991 Norms143.518- 1996 Norms11.22.414.4- stage 2000 Norms4.51.18.00.36 Bharat stage-II4.01.17.00.15 Bharat Stage-III2.11.65.00.10 Bharat Stage-IV1.50.963.50.02 A move to Bharat Stage IV+ from 2016, before moving to Bharat Stage V in 2021Bharat Stage V