MECH 435: Internal Combustion Engines
Assignment 3 – Combustion Theory
Due: March 25, 2011
1. Methyl alcohol (CH3OH) burns with excess air at an air-fuel ratio (mass) of 8.0.
Determine the equivalence ratio and the mole fraction of CO2 in the product mixture
assuming complete combustion.
2. Determine the enthalpy of formation in kJ/kmol for methane, given the lower heating
value of 50,016 kJ/kg at 298 K.
3. If a lean ( = 0.8) mixture of methane is burned at a temperature of 1500K and
pressure of 500 kPa producing CO2, H2O, O2, N2. Calculate by hand the mole fraction of
the products, then use the applet to calculate the equilibrium mole fractions, comment on
the difference if any between the two sets of values.
4. At what temperature does the mole fraction of NO reach 0.01 for the equilibrium
products resulting from the combustion of gasoline and air at =1.0 at 5000 kPa (use
Applet).
5. What is the residual mass fraction required to reduce the adiabatic flame temperature
of gasoline, diesel, methane, methanol, and nitromethane below 2000K? Take  = 1.0 at
101 kPa and 298K (use Applet).
6. Equilibrium combustion products at  = 1.0 of methane are expanded isentropically
from 2000K and 1000 kPa to a pressure of 100 kPa. Find the final temperature and the
work done (use Applet).