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ME476_HW5_Soln

ME476_HW5_Soln - MCAD Definitions kJ:= 10 J 3 MJ:= 10 J 6...

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AF 17.284mol = Compare to values in table D-4 A/F= 17.23 F/A= 0.580 LHV= 50.0 MJ/kg FA 1 AF = FA 0.058mol -1 = OR EQ 3.6 for CH fuels ONLY ( does NOT apply to #C or D ) y 4 1 = AF 34.56 4 y + ( ) 12.011 1.008y + = AF 17.234 = LHV H P o H R o - = P n i h f.i o R n i h f.i o - = Products Reactants Species n i ? h f,i o n i *?h f,i o Species n i ? h f,i o n i *?h f,i o CO2 1 -393.5 -393.5 CH4 1 -74.9 -74.9 H2O 2 -241.8 -483.6 O2 2 0 0 N2 7.546 0 0 N2 7.546 0 0 H P o -877.1 H R o -74.9 LHV 877.1 - MJ kmol 74.9 - ( ) MJ kmol - = LHV 802.2 - MJ kmol = Note: per kg FUEL Negative because heat is RELEASED during combustion (Q.out) convert to MJ/kmol & Positive Qout LHV M fuel 1 - ( ) 50.138 MJ kg = LHV from back of book is 50.0! Differences are due mainly to rounding of Molar masses MCAD Definitions kJ 10 3 J = MJ 10 6 J = kmol 10 3 mol = 3.11 Using the combustion equation, determine A/F, F/A and LHV for stoichiometric mixture of: a) methane CH4 b) isooctane C8H18 c) Hydrogen H2 d) methyl alcohol CH3OH Given M O2 32 gm mol = M N2 28 gm mol = M H2 2 gm mol = M CO2 12 gm mol = Start by writing combustion equations for each fuel. A/F ratio and LHV (or HHV) can be determined from the combustion equation. A-) CH 4 2 O 2 3.773 N 2 + ( 29 + CO 2 2H 2 O + 7.564N 2 + = n air 2 4.773 mol = n fuel 1 = M air 28.97 gm mol = M fuel 1 M CO2 2 M H2 + = AF n air M air n fuel M fuel =

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