A gas turbine works on an ideal Brayton cycle with pressure ratio and

PHYSICS · Multi-part · Fermi University Physics · Thermal, Statistical & Complex Systems · Earth, Climate & Energy Physics · The laws of thermodynamics

Energy from Physics, Ch Heat engines on fuel: exergy, real cycles, biomass and the nuclear heat source

Problem

A gas turbine works on an ideal Brayton cycle with pressure ratio rp=15r_p = 15 and γ=1.4\gamma = 1.4. A steam cycle of efficiency ηR=0.33\eta_R = 0.33 recovers all the heat in its exhaust. ((a)) Find the ideal Brayton efficiency ηB\eta_B and the combined-cycle efficiency ηcc\eta_{\rm cc}. ((b)) A real gas turbine at this pressure ratio reaches only ηB=0.38\eta_B = 0.38 once compressor and turbine losses are counted. With the same steam cycle, find ηcc\eta_{\rm cc}. ((c)) The plant burns methane, which releases 55 g55\,\mathrm{g} of CO2\mathrm{CO_2} per megajoule of heat. Find the real plant's emissions per kilowatt-hour of electricity.

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