Stochiometry of Real Combustion P M V Subbarao Professor Mechanical Engineering Department A First Step to Understand &Control Rate of Heat Release ….

Stochiometry of Real Combustion

P M V SubbaraoProfessor

Mechanical Engineering Department

A First Step to Understand &Control Rate of Heat Release ….

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What is the optimal air/fuel ratio for Better HR ?

What Parameters control the HRR ?

Structure of Ford Research simulation.

Thermo Chemical Equilibrium

Fuel Model

• Ultimate Analysis of fuel: Gravimetric

• C : 84 -- 87% ; H : 11 -- 16% ; O : 0.3 -- 1.8% ; N : 0.1 -- 1.5% ; S : 0.1 -- 3%

• 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 gms.

• Liquid and gaseous fuels generally have very little sulfur, oxygen and moisture.

• Generally popular chemical formulae: CXHY

Ideal combustion

CXHY + 4.773 (X+Y/4) AIR → P CO2 +Q H2O + R N2

Molecular weight of fuel : YXM fuel 008.1011.12

Homogeneous Mixture model for Air:

22 773.3 1 Air of 773.4 NofkmolesOofkmolekmoles

Molecular weight of Air : 96.28773.4

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Equivalence Ratio

• The equivalence ratio of a system is defined as the ratio as the ratio of the actual fuel/air ratio to the stoichiometric ratio.

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Universal Law for Completion of Reaction

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Theoretical Prediction of Combustion Products: Pure Iso-Octane @ 5.0 MPa

Theoretical Prediction of Combustion Products: Pure Iso-Octane @ 5.0 MPa

Theoretical Prediction of Combustion Products: Pure Iso-Octane @ 5.0 MPa

Equilibrium Products at High Pressure 30 atm :Octane

Equilibrium Products at High Pressure 30 atm : Octane

Equilibrium Products at High Pressure 30 atm : Octane

Theoretical Prediction of Combustion Products: Pure Cetane

Real Combustion & Model Testing

Results of Model Testing.

• For a given fuel and required steam conditions.

• Optimum composition of Exhaust Gas.

• Optimum air flow rate.

• Optimum fuel flow rate.

• Optimum combustion configuration!!!

Molar Analysis of Dry Exhaust Products:• Mole fraction of CO2 : x1 • Mole fraction of CO : x2

• Mole fraction of O2 : x4

• Mole fraction of N2 : x5