A 20 MW back-pressure steam turbine receives steam at stagnation pressure of 4 MPa and stagnation temperature of 300oC, exhausting from the last stage at stagnation pressure of 0.35 MPa. The turbine isentropic efficiency is 0.884, and mechanical losses are 2% of the actual enthalpy drop. Sketch the expansion process in Mollier diagram. Determine the rate of steam flow.
At the exit from the first stage nozzles the steam velocity is 244 m/s, specific volume 0.0686 m3 /kg, mean diameter 762 mm and steam angle 76o measured from the axial direction. Determine the nozzle height of this stage.