Question

. In a gas turbine plant, air enters a compressor at atmospheric conditions of 15 ?C, 1.0133 bar and is compressed through a pressure ratio of 10. The air leaving the compressor passes through a heat exchanger before entering the combustion chamber. The hot gases leave the combustion chamber at 800 ?C and expand through an HP turbine which drives the compressor. On leaving the HP turbine the gases pass through a reheat combustion chamber which raises the temperature of the gases to 800 ?C before they expand through the power turbine, and hence to the heat exchanger where they flow in counter-flow to the air leaving the compressor. Using the data below, neglecting the mass flow rate of fuel and changes of velocity throughout,

calculate: (i) The airflow rate required for a net power output of 10 MW;

(ii) The work ratio of the cycle;

(iii) The temperature of the air entering the first combustion chamber;

(iv) The overall cycle efficiency.

Data: Isentropic efficiency of compressor, 80 %; isentropic efficiencies of HP and power turbine, 87 and 85 %; mechanical efficiency of HP turbine-compressor drive, 92 %; mechanical efficiency of power turbine drive, 94 %; thermal ratio of heat exchanger, 0.75; pressure drop on air side of heat exchanger, 0.125 bar; pressure drop in first combustion chamber, 0.100 bar; pressure drop in reheat combustion chamber, 0.080 bar; pressure drop on gas side of heat exchanger, 0.100 bar.

ANSWERS(91.0 kg/s; 0.25; 611 ?C; 18.9 %)

Answer 1