This is a sample calculation of work and thermal efficiency of a jet engine given the following conditions:

Temperature of the air entering the compressor (TA) = 298K
Pressure of air entering the compressor (PA) = 0.1 MPa
Pressure of the air leaving the compressor (PB) = 0.6 MPa
Temperature of the air entering the turbine (TC) = 973K
Turbine and Compressor operate at efficiencies of 0.85
The following assumptions are made to simplify calculations:
  1. Ideal Gas
  2. Compressor and turbine are adiabatic and reversible
  3. Constant pressure heat addition
The heat capacity used for air in the problem is Cp/R =3.51 (0.79*CpN2 + 0.21*CpO2)

The best method for solving is to break the engine into its components and solve for WS or Q at each step.

Step 1: Adiabatic Compression from A to B

Step 2: Constant Pressure Heat addition from B to C

Step 3: Adiabatic Expansion from C to D

Calculation for Net Work

Calculation for Thermal Efficiency