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Thermodynamics & Gas dynamics of Real Combustion in Turbo Combustor P M V Subbarao Professor Mechanical Engineering Department Tools for precise estimation of fuel-air ratio….

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Thermochemistry of Combustion

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Modeling of Ideal Combustion

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Modeling of Actual Combustion

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Modeling of 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 Exhaust gases: P CO 2 +QH2O+R SO 2 + T N 2 + U O 2 + V CO kmols. Excess air coefficient : . Emission measurement devices indicate only Dry gas volume fractions. Volume fraction = mole fraction or ppm Volume fraction of CO 2 : x 1 = P * 100 /(P+R + T + U + V) Volume fraction of CO : x 2 = VCO * 100 /(P +R + T + U + V) Volume fraction of SO 2 : x 3 = R * 100 /(P +R + T + U + V) Volume fraction of O 2 : x 4 = U * 100 /(P +R + T + U + V) Volume fraction of N 2 : x 5 = T * 100 /(P +R + T + U + V) These are dry gas volume fractions.

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Emission Standards 15% oxygen is recommended in exhaust. NO x upto 150 ppm. SO 2 upto 150 ppm. CO upto 500 ppm. HC upto 75 ppm. Volume fractions of above are neglected for the calculation of specific heat flue gas.

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Specific Heat of flue gas :

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For a given mass flow rate of fuel and air, the temperature of the exhaust can be calculated using above formula. If mass flow rates of fuel and air are known. Guess approximate value of specific heat of flue gas. Calculate T 0,ex. Calculate c p,flue gase. Re calculate T 0,ex. Repeat till the value of T 0,ex is converged.

11 Total Pressure Loss in Turbo Combustor The loss of pressure in combustor (p 0,ex

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Gas Dynamic Studies on Combustors Effect of heat generation on one dimensional ideal compressible flow. Effect of varying mass flow rate. Effect of combined heat generation and friction.

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Frictional Flow with Heat Transfer

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Governing Equations no body forces, viscous work negligible Conservation of mass for steady flow: Conservation of momentum for frictional steady flow : Conservation of energy for steady flow :

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Ideal Gas law : Mach number equation :

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Simplification of Continuity Equation

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Simplification of Momentum Equation

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Combined Momentum and Continuity Equation

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Constant flow rate, Constant Area, Non-reacting, Steady Compressible Flow with Friction Factor and Heat Generation Constant flow rate, Constant Area, Non-reacting, Steady Compressible frictionless Flow with Heat Generation

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Supersonic RAM Jets Variation of Stagnation Temperature

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