2. Fuel-Air Modeling of Combustion in I.C. Engines P M V Subbarao Professor Mechanical Engineering Department Another Step towards Phenomenological Modeling.….

3. Phenomenological Modeling of Combustion Engineering Objective of Combustion: To Create Maximum Possible Temperature through conversion of microscopic potential energy into microscopic kinetic energy. Thermodynamic Strategy for conversion: Constant volume combustion Constant pressure combustion

4. Engineering Strategy to Utilize A Resource Engineering constraint: Both combustion and expansion have to be finished in a single stroke. Rapid combustion : Constant Volume combustion –Less time to combustion process. –More time to adiabatic expansion Slow combustion : Constant pressure combustion –More time to combustion process. –Less time to adiabatic expansion

5. 2—3 Complete & Adiabatic combustion at constant volume 0 0

6. 2—3 Complete & Adiabatic combustion at constant pressure 0

7. Generalized Theory of Extent of Reaction Possible Extent of Reaction Entropy of Universe p 1,T 1 p 2,T 2 p 3,T 3

8. Mathematical Model for Culmination of Reaction For every fuel, a designer should know all possible reactants !!! Some products will influence the efficiency of reaction. Few other may not influence the efficiency of reaction but severely affect the environment. The optimal parameters for efficient reaction may not be optimal for safe reaction !! There may be a need to use secondary reactor with catalysts. Catalytic Converter Possible extent of reaction:

9. BS-IV-- Petrol and Diesel BS-IV Petrol and Diesel are cleaner fuels as they have low sulphur content vis-à-vis BS-III fuels. While the BS-III Petrol and Diesel contain 150 mg/kg and 350 mg/kg of sulphur respectively, the sulphur content in BS-IV Petrol and Diesel respectively. Sulpur being a major air pollutant, reduction in sulphur content in auto fuels would go a long way in reducing air pollution in Delhi 8 https://www.araiindia.com/pdf/Indian_Emission_Regulation_Booklet.pdf

10. How to predict possible products of combustion??? How to control the concentration??

11. Rapid Reaction to Very Slow Action

12. Formation of Fossil Fuels

13. Sorry !!! We Don’t Know How To Use Crudes !!!

14. Sorry !!! We Don’t Know How To Produce What we Precisely Need !!! BOILING RATE # CARBON ATOMS Refinery Gas <25 o C 3 Gasoline 40-150 o C 4-10 Naptha 150-200 o C 10-12 Kerosene 200-300 o C 12-16 Diesel Fuel 300-400 o C 16-25 Residual Oil >400 o C >25

15. Other components of Gasoline Name of Hydro- carbon Sample 1Sample 1Sample 2Sample 2Sample 3Sample 3 Ethanol 13.40%12.10% 10.20% 2-methyl-pentane 10.20%4.50% 4.50% Hexane Hexane 0%2.10% 0% Benzene Benzene 0% 0% 7% Toluene Toluene 0%0% 8.20% pentane pentane 5.50%3.70% 0%

16. Fuel Model & Ideal Combustion Ultimate Analysis of fuel: Gravimetric Percentage of carbon : x --- Number of moles, X = x/12 Percentage of hydrogen : y --- Number of atomic moles, Y = (y- M/9)/1 Percentage of oxygen: k --- Number of atomic moles, K = (k- 8M/9)/16 Percentage of sulfur: z – Number of atomic moles, Z = z/32 Equivalent chemical formula : C X H Y S Z O K Equivalent Molecular weight : 100 kg. Ideal combustion with oxygen C X H Y S Z O K + (X+Y/4+Z-K/2) O 2 → P CO 2 +Q H 2 O + G SO 2 Ideal combustion with air C X H Y S Z O K + 4.76 (X+Y/4+Z-K/2) AIR → P CO 2 +Q H 2 O + R N 2 +G SO 2

17. Modeling of Field Level Combustion C X H Y S Z +  4.76 (X+Y/4+Z) AIR + Moisture in Air + Moisture in fuel → P CO 2 +Q H 2 O +R SO 2 + T N 2 + U O 2 +V CO+WCH 4 Exhaust gases: P CO 2 +QH 2 O+R SO 2 + T N 2 + U O 2 + V CO+WCH 4 kmols. Excess air coefficient: . Volume fraction = mole fraction. Volume fraction of CO 2 : x 1 = P * 100 /(P+Q+R + T + U + V+W) Volume fraction of H 2 O: x 1 = Q * 100 /(P+Q+R + T + U + V+W) Volume fraction of CO: x 2 = V * 100 /(P +Q+R + T + U + V+W) Volume fraction of O 2 : x 4 = U * 100 /(P +Q+R + T + U + V+W) Volume fraction of N 2 : x 5 = T * 100 /(P +Q+R + T + U + V+W)

18. Closure on Analysis of Combustion Complete & Adiabatic combustion at constant volume Complete & Adiabatic combustion at constant pressure Design of sub-systems for better combustion needs more detailed analysis of thermo-physical & thermo chemical processes preceding and during combustion.