# Homework Help: Deriving Efficiency Of A Diesel Engine Formula

1. Oct 26, 2012

1. The problem statement, all variables and given/known data
The Diesel cycle is an idealized representation of the process that occurs in a Diesel combustion engine, as shown in the graph below. Starting at point a, the Diesel cycle consists of an adiabatic compression, an isobaric expansion, and adiabatic expansion and an isochoric cooling. Find the efficiency in terms of only the compression ratio, r = Va/Vb, γ (gamma), THot and TCold. Show all work!

2. Relevant equations
e = 1 + QC/QH
γ (gamma) = cp/cv
dQ = dU + dW

For adiabatic expansion, TVγ-1 = constant, if the number of moles is constant PVγ = C where C is a constant.

Work for adiabatic process = W = (C/1-γ)(V21-γ - V11-γ)

3. The attempt at a solution
I am having problems starting up with this problem and writing it in terms of temperature. I know that temperature at Ta is equal to Tc which in turn is equal to TH from what I know. But, how do I begin after setting up the problem like this? I am sorry for not providing a "thorough" attempt at a solution; I am having problems at the initial steps which is why I can't do much. Any light on this problem would be appreciated.