HW4_soln - 6. Calculate the stoichiometric AF ratio and...

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Unformatted text preview: 6. Calculate the stoichiometric AF ratio and lower heating value for E85 fuel [85% ethanol+15% gasoline (C8H15), by VOLUME]. Use the relevant data in Table A.2. Assume the density of ethanol is 0.79 gm/cm3 and gasoline fuel density is 0.74 gm/cm3. Define A = ethanol, B = gasoline From table A‐2: MA = 46, MB = 111, LHVA = 26950, LHVB = 43000 ρ A = 0.85 × 0.79 = 0.6715 gm / cm3 ρB = 0.15 × 0.74 = 0.111 gm / cm3 mA = nA = ρA = 0.858 , mB = 1 − mA = 0.142 ρ A + ρB NA mA / M A 0.858 / 46 = = = 0.936 N A + N B mA / M A + mB / M B 0.858 / 46 + 0.142 / 111 nB = 1 − n A = 0.064 n A ⋅ C2 H 6O + nB ⋅ C8 H15 + U (O2 + 3.76 N 2 ) → 3.76U ⋅ N 2 + D ⋅ H 2O + E ⋅ CO2 C: 2nA + 8nB = E H: 6n A + 15nB = 2 D O: n A + 2U = D + 2 E ⇒ 2U = 6nA + 15nB + 2(2nA + 8nB ) − nA 2 ⇒ U = 3.57 AF = 3.57(32 + 3.76 × 28) 490.09 = = 9.77 0.936 × 46 + 0.064 × 111 50.16 LHV = 0.858(26950) + 0.142(43000) = 29229 ...
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This note was uploaded on 03/10/2009 for the course MAE 408 taught by Professor Fang during the Fall '08 term at N.C. State.

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