Fall 2017 MENG 0312-Thermodynamics II Problem Set # 4 1. Air enters the compressor of a regenerative air-standard Brayton cycle with a volumetric flow rate of 60 m3/s at 0.8 bar and 280 K. The compressor pressure ratio is 20 and the maximum cycle temperature is 2100 K. For the compressor, the isentropic efficiency is 92% and for the turbine the isentropic efficiency is 95%. For a regenerator effectiveness of 85%, determine a) the net power developed, in MW b) the rate of heat addition in the combustor, in MW c) the thermal efficiency of the cycle 10 2. Air at 26 kPa, 230 K and 220 m/s enters a turbojet engine in flight. The air mass flow rate is 25 kg/s. The compressor pressure ratio is 11, the turbine inlet temperature is 1400 K and air exits the nozzle at 26 kPa. Assume that diffuser and nozzle processes are isentropic. The compressor and turbine have isentropic efficiencies of 85% and 90%, respectively and there is no pressure drop for flow through the combustor. Kinetic energy is negligible everywhere except at the diffuser inlet and the nozzle exit. Determine a) the pressures in, kPa, and temperatures, in K, at each principal state. b) the rate of heat addition to the air passing through the combustor, in kJ/s c) the velocity at the nozzle exit, in m/s d) net thrust, propulsive power and propulsion efficiency 10