Question

It is desired to an alyze the performacne of a gas turbine engine operating on a Bratyon cycle with a free power turbine. The engine is under test at static conditions with an ambient temperature of 20'C and pressure of 1atm. The pressure ratio of the compressor is 5. The engine burnsmethane fuel with a heat of combustion of 50MJ/kg. The air to fuel ratio (AF) is 45. Assume the pressure at the inlet to the compressor is equal to the ambient pressure. The efficiencies of the compressor, high pressure (HP) turbine, and free turbine respectively are .85, .88, .82. Complete the following steps:

1. Vary AF from 20 to 60 in steps of 2 and compute the temperature at the inlet to the HP turbine nconsidering the actual cycle. Make a plot of the same. Comment on results.

2. Now, consider two values of AF: 35 and 45. For each of these AF values, consider compressor pressure ratios from 2 to 100 in increments of 2.

a. Considering the actual cycle, compute the thermal efficiency and work output from the free turbine per unit mass at each pressure ratio for both values of AF.

b. Make a plot showing the thermal efficiency as a function of pressure ratio for each AF.

c. Make a plot showing the work output from the free turbine per unit mass as a function of pressure ratio for each AF.

d. Comment on the plots and the value of pressure ratio that gives you the maximum efficiency or the maximum free turbine work output per unit mass.

Answer 1