Question

Consider the effects of exhaust gas recirculation on the combustion process. Mixing exhaust gas with the fuel-air gas changes the initial temperature, density, molecular weight and effective heat of combustion of the charge within an SI engine.
Consider an SI engine with compression ratio 9 which uses fuel-air mixture of the equivalence ratio 1.1. The fuel-air mixture enters the intake manifold at a pressure p1 and temperature 290K. Perform an analysis of the effect of EGR on an ideal cycle. Assume the intake and exhaust processes both occur at the same pressure of 1atm.(fuel C3H8)
a) Use a major product model to determine the composition of the EGR. Note: For the remaining questions, carry out the STANJAN computations for an EGR mass fraction of 0, 10, 20 and 30%. Assume that the charge only consists of EGR and fuel-air.
b) Assuming that the recirculated exhaust is at a pressure of 1 bar and a temperature of 900 K, compute the temperature of the fuel-air-EGR mixture before it enters the cylinder (State 1).
c) Carry out an adiabatic compression computation to determine the pressure and temperature at the end of the compression stroke (State 2).
d) Perform a constant-volume combustion computation to determine the peak pressure and temperature (State 3). Use full set of products to determine states 3 and 4.
e) Perform an adiabatic expansion computation to find the final pressure and temperature at the end of the expansion stroke (State 4).
f) Use the computed energies in states 1 and 4 to find the work per cycle expressed as IMEP (Indicated Mean Effective Pressure).
g) Show the effect of EGR on the combustion process using the graphs of your choice

Answer 1