In a gas turbine unit comprising L.P. and H.P. compressors, air is taken at 1.01 bar 27°C. Compression in L.P. stage is upto 3.03 bar followed by intercooling to 30°C. The pressure of air after H.P. compressor is 58.7 bar. Loss in pressure during intercooling is 0.13 bar. Air from H.P. compressor is transferred to heat exchanger of effectiveness 0.60 where it is heated by gases from L.P. turbine. The temperature of gases supplied to H.P. turbine is 750°C. The gases expand in H.P. turbine to 3.25 bar and are then reheated to 700°C before expanding in L.P. turbine. The loss of pressure in reheater is 0.1 bar. If isentropic efficiency of compression in both stages is 0.80 and isentropic efficiency of expansion in turbine is 0.85, calculate : (i) Overall efficiency (ii) Work ratio (iii) Mass flow rate when the gas power generated is 6500 kW. Neglect the mass of fuel. Take, for air : cp = 1.005 kJ/kg K, γ = 1.4 for gases : cpg = 1.15 kJ/kg K, γ = 1.3. [Ans. (i) 16.17% (ii) 0.2215 (iii) 69.33 kg of air/sec.]
In a gas turbine unit comprising L.P. and H.P. compressors, air is taken at 1.01 bar 27°C. Compression in L.P. stage is upto 3.03 bar followed by intercooling to 30°C. The pressure of air after H.P. compressor is 58.7 bar. Loss in pressure during intercooling is 0.13 bar. Air from H.P. compressor is transferred to heat exchanger of effectiveness 0.60 where it is heated by gases from L.P. turbine. The temperature of gases supplied to H.P. turbine is 750°C. The gases expand in H.P. turbine to 3.25 bar and are then reheated to 700°C before expanding in L.P. turbine. The loss of pressure in reheater is 0.1 bar. If isentropic efficiency of compression in both stages is 0.80 and isentropic efficiency of expansion in turbine is 0.85, calculate :
(i) Overall efficiency
(ii) Work ratio
(iii) Mass flow rate when the gas power generated is 6500 kW. Neglect
the mass of fuel.
Take, for air : cp = 1.005 kJ/kg K, γ = 1.4
for gases : cpg = 1.15 kJ/kg K, γ = 1.3.
[Ans. (i) 16.17% (ii) 0.2215 (iii) 69.33 kg of air/sec.]
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