A gas power plant operates a gas turbine, which is modelled as an ideal Brayton cycle. At the compressor inlet, a mixtur

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A Gas Power Plant Operates A Gas Turbine Which Is Modelled As An Ideal Brayton Cycle At The Compressor Inlet A Mixtur 1 (77.18 KiB) Viewed 32 times

A gas power plant operates a gas turbine, which is modelled as an ideal Brayton cycle. At the compressor inlet, a mixture of natural gas and air is drawn in at a pressure of 5 bar at 32°C. After combustion, the temperature of the gas reaches 2800°C. You may assume that the working fluid is an ideal gas, with Rg = 0.301 kJ/kg/K and y = 1.42. (a) Determine the required pressure ratio if the specific heat addition is 1800 kJ/kg. What is the resulting thermal efficiency and work ratio? (7 marks) (b) The gas inlet duct has a cross-sectional area of 3.5 m², determine the mass flow and flow velocity of the gas mixture in the inlet duct, given that the turbine provides a net power output of 10 MW. (4 marks) (c) A regenerative heat exchanger is added to increase the thermal efficiency of the turbine. 10% of the excess heat from the exhaust is lost to the surroundings before the heat exchanger and after the heat exchanger, the compressed gas and exhaust are at thermal equilibrium (Ti = T). Determine this equilibrium temperature, T3, the specific heat exchanged as well as the new thermal efficiency and work ratio. (10 marks) Explain under what conditions a regenerative heat exchanger wouldn't be able to increase the thermal efficiency of the turbine. At what is the pressure ratio and thermal efficiency when a regenerative heat exchanger stops improving efficiency? You may assume that the specific heat addition does not change and neglect any heat loss for the exhaust gases prior to the heat exchanger (4 marks) (d)