In: Mechanical Engineering
In a marine gas turbine unit a high-pressure turbine drives the compressor, and a low-pressure turbine drives the propeller through suitable gearing. The overall pressure ratio is 4/1, and the maximum temperature is 650⁰C. The isentropic efficiencies of the compressor, High Pressure turbine, and Low Pressure turbine are 0.8, 0.83 and 0.85 respectively, and the mechanical efficiency of both shafts is 98%.
Calculate the pressure entering the Low Pressure turbine when the air intake conditions are 1.01 bar and 25⁰C. Calculate also the thermal efficiency and the shaft power when the mass air flow is 60 kg/s. Neglect kinetic energy changes, and the pressure loss in combustion.
For all compression processes take cp = 1.005 kJ/kg K and ɣ=1.4; for the combustion and expansion processes take cp = 1.15 kJ/kg K and ɣ=1.333. Neglect the mass of fuel.