Impact of 20 th Century Research on Combustion & Evolution of I.C. Engines

1. Impact of 20th Century Research on Combustion & Evolution of I.C. Engines P M V Subbarao Professor Mechanical Engineering Department Engineering of A Quick & Comprehensive Phenomenon…...

2. Formula 1 Car • The internal combustion engine of a Formula One car must 1.6-litres in capacity and rev-limited to 15,000rpm. • The engine must also have six cylinders arranged in a 90-degree formation, with two inlet and two exhaust valves per cylinder and a single turbocharger.

3. Hydro carbon Chemistry of Crude Oils • Components of Crude Oils. • Paraffins (CnH(2n+2)) • Olefins • Aromatics • Ultimate Analysis • C : 84 -- 87% ; H : 11 -- 16% ; O : 0.3 -- 1.8% ; N : 0.1 -- 1.5% ; S : 0.1 -- 3%

4. Important Fuel Derivatives from Crude Oil

5. Boiling range, and molecule size for typical refinery • BOILING RATE # CARBON ATOMS • Refinery Gas <25oC 3 • Gasoline 40-150oC 4-10 • Naptha 150-200oC 10-12 • Kerosene 200-300oC 12-16 • Diesel Fuel 300-400oC 16-25 • Residual Oil >400oC >25

6. Major Components of Gasoline (Petrol)

7. Major Components of Gasoline (Petrol)

8. Fuel Model & Ideal Combustion • Ultimate Analysis of dry (moisture free) fuel: Gravimetric • Percentage of carbon : x --- Number of moles, X = x/12 • Percentage of hydrogen : y --- Number of atomic moles, Y = y/1 • Percentage of oxygen: k --- Number of atomic moles, K = k/16 • Percentage of sulfur: z – Number of atomic moles, Z = z/32 • Equivalent chemical formula : CXHYSZOK • Equivalent Molecular weight : 100 kgs. • Ideal combustion • CXHYSZOK + 4.76(X+Y/4+Z-K/2) AIR→ P CO2 +Q H2O + R N2 + G SO2 • Air- Fuel Ratio:

9. Stoichiometric Ideal Combustion • Mass of fuel = one kilo mole = 100 kg : Equivalent chemical formula. • Chemically exact amount of air for ideal combustion of one kilo morel air. • Stoichiometric air fuel ratio is the ratio of exact mass of air required to mass of fuel.

10. The True Process of Methane Combustion Overall reaction for the combustion of methane is given by: True Reaction Mechanisms: True Reaction mechanisms are composed of a series of elementary processes (steps) which are indicative of the molecular encounters. A detailed kinetic mechanism revealed 213 elementary reactions and 48 species. Another critical review showed 325 elementary reactions. The first two steps in the combustion of methane are given by: Interestingly, mechanisms are never proven but rather postulated and checked for consistency with observed experimental kinetic data.

11. 9-Step reduced mechanism for Methane Combustion

12. Recognition of Actual Air Fuel Ratio Define equivalence Ratio as the ratio of the actual fuel/air ratio to the stoichiometric fuel/air ratio.

13. Pre-processing of fuel & Air Vs Combustion Mechanism Pre mixing of fuel and air No Pre mixing of fuel and air Partial Pre mixing of fuel and air

14. Status of Fuel & Air Before Onset of Combustion

15. Care for Occurrence of Combustion • Occurrence of combustion in SI Engine : A Child Care Event. • Occurrence of combustion in CI Engine: A Teen Care Event. SI Engine CI Engine

16. Engineering of Ignition Temperature 25 C 0 

17. Type of Fuel Vs Traditional Combustion Strategy • Highly volatile with High self Ignition Temperature: Spark Ignition. Ignition after thorough mixing of air and fuel. • Less Volatile with low self Ignition Temperature: Compression Ignition , Almost simultaneous mixing & Ignition.