he overall compression ratio in a gas turbine engine is 12/1 which is performed in three stages with pressure ratios of 2.5/1, 2.4/1, and 2/1 respectively. The air inlet temperature to the plant is 25 °C and intercooling between stages reduces the temperature to 40 °C. The HP turbine drives the HP and intermediate-pressure compressor stages; the LP turbine drives the LP compressor and the generator. The gases leaving the LP turbine are passed through a heat exchanger which heats the air leaving the HP compressor. The temperature at the inlet to the HP turbine is 650 °C, and reheating between turbine stages raises the temperature to 650 °C. The gases leave the heat exchanger at a temperature of 200 °C. The isentropic efficiency of each compressor stage is 0.83, and the isentropic efficiencies of the HP and LP turbines are 0.85 and 0.88 respectively. Take the mechanical efficiency of each shaft as 98%. The air mass flow is 346 kg/s. Neglecting pressure losses and changes in kinetic energy, and taking the specific heat of the water as 4.19 kJ/kg K. For the compression process take cp = 1.005 kJ/kg K and γ = 1.4; for the combustion process, and for the expansion process take cp = 1.15 kJ/kg K and γ = 1.333. Neglect the mass of fuel. (ii) Calculate the cycle efficiency; (iii) Calculate the flow of cooling water required for the intercoolers when the rise in water temperature must not exceed 30 K;
The overall compression ratio in a gas turbine engine is 12/1 which is performed in three
stages with pressure ratios of 2.5/1, 2.4/1, and 2/1 respectively. The air inlet temperature
to the plant is 25 °C and intercooling between stages reduces the temperature to 40 °C. The
HP turbine drives the HP and intermediate-pressure compressor stages; the LP turbine
drives the LP compressor and the generator. The gases leaving the LP turbine are passed
through a heat exchanger which heats the air leaving the HP compressor. The temperature at
the inlet to the HP turbine is 650 °C, and reheating between turbine stages raises the
temperature to 650 °C. The gases leave the heat exchanger at a temperature of 200 °C. The
isentropic efficiency of each compressor stage is 0.83, and the isentropic efficiencies of the
HP and LP turbines are 0.85 and 0.88 respectively. Take the
shaft as 98%. The air mass flow is 346 kg/s. Neglecting pressure losses and changes in kinetic
energy, and taking the specific heat of the water as 4.19 kJ/kg K. For the compression process
take cp = 1.005 kJ/kg K and γ = 1.4; for the combustion process, and for the expansion process
take cp = 1.15 kJ/kg K and γ = 1.333. Neglect the mass of fuel.
(ii) Calculate the cycle efficiency;
(iii) Calculate the flow of cooling water required for the intercoolers when the rise in
water temperature must not exceed 30 K;
iv) Calculate the heat exchanger thermal ratio.
Note: Numerical answers till the 3rd decimal are required to be written.
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