Air enters the compressor of a regenerative gas-turbine engine at 300 K and 100 kPa, where it is compressed to 800 kPa and 580 K. The regenerator has an effectiveness of 72%, and the air enters the turbine at 1200 K. For a turbine efficiency of 86%, determine (a) the amount of heat transfer in the regenerator and (b) the thermal efficiency of the cycle. 3. Consider a gas-turbine cycle with two stages of compression and two stages of expansion. The pressure ratio across each stage of the compressor and turbine is 3. The air enters each stage of the compressor at 300 K and each stage of turbine at 1200 K. The isentropic efficiency for each compressor stage is 80% and the isentropic efficiency for each turbine stage is 85%. Determine the back work ratio and the thermal efficiency of the cycle, assuming (a) no regenerator is used and (b) a regenerator with 75% effectiveness is used. 4. Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kPa and 17oC. The system uses a regenerator as well as reheating and intercooling. The pressure ratio across each compressor is 4. 300 kJ/kg of heat are added to the air in each combustion chamber. The regenerator increases the temperature of the cold air by 20oC. Determine the thermal efficiency of the system assuming isentropic operations for all compressor and turbine stages and using constant specific heats at room temperature.