Question

A combined power cycle relies on a gas turbine cycle and a Rankine cycle. Heat is fed to the gas turbine combustor at a rate of 50 MW. The gas turbine cycle operates at an efficiency of 0.35. The gas that exhausts from the turbine is still hot and is used to boil water in the Rankine cycle. The Rankine cycle operates at an efficiency of 0.42. Find: a) The total power produced by the combined cycle b) The efficiency of the combined cycle c) The rate of heat rejection from the Rankine cycle d) If the Rankine boiler is operating at a pressure of 2 MPa and the steam enters the turbine at a temperature of 300 C, what is the mass flow rate of water through the Rankine engine? You may assume that the water leaving the pump is saturated liquid at 2 MPa.

please explain the reasoning behind each step as well. thank you

Answer 1

supplied ginen gas turbine heat Os = SOMW (gas) = 0.35 (MRT = 0.42 Whet gas) cycle = Os. Whet = 0.35x50 I wnet = 17.5MWI gas cycle. the gas turbine cycle Whet = 17.5 mW Obtain. from and heat rejeted by gas tubine acle is used boil of water in Rankine cycle.

OR = Os- Whet OR = 50-17.5 TOR = 32.5 MW 2.5 MWL = we know that (Rcycle = 0.42 (MR) cycle = whet (Whet) R = Whet) R = 0.42 x 32.5 13.65 MW. The total power produced by the combined cycle Wtotal = (13.657 14:5) TwTotal = 31.15 mW

o of combined The efficiency cycle I god ) c = 0.35 (R) c = 0.42 DATA I comb = -(1-0.35] (1-0.42) comb = - 0.65% 0.58 In comb = 0.6404 | from © The rate of heat rejected the pankine cycle OR = OR (WR) net = 32.5-13.65 Toe = 18.85 mW mann

from steam table p=2MPa T=300°c h = 3024.2 kg kg ha = 908. 47k1 kg Os = m Chi-ha) - m (3024.2 - 908.47) 32.5x100 = 2115.73M m = 32.5x106 2 115.73 m = 15:36 49's Ang