In a marine gas turbine unit a high-pressure turbine drives thecompressor, and a low-pressure turbine drives the propeller throughsuitable gearing. The overall pressure ratio is 4/1, and themaximum temperature is 650â°C. The isentropic efficiencies of thecompressor, High Pressure turbine, and Low Pressure turbine are0.8, 0.83 and 0.85 respectively, and the mechanical efficiency ofboth shafts is 98%.
Calculate the pressure entering the Low Pressure turbine whenthe air intake conditions are 1.01 bar and 25â°C. Calculate also thethermal efficiency and the shaft power when the mass air flow is 60kg/s. Neglect kinetic energy changes, and the pressure loss incombustion.
For all compression processes take cp =1.005 kJ/kg K and ɣ=1.4; for the combustion and expansion processestake cp = 1.15 kJ/kg K and ɣ=1.333. Neglect themass of fuel.
