Question

A power plant operates one of its steam turbines at a speed of 1800rpm and a steam flow of 139 kg/s with a nozzle velocity coefficient (K) of 0.96. The inlet and outlet steam pressures are 69 bar and 27.6 bar, respectively. Windage and leakage losses are noted to be 3%. The turbine blades are oriented such that the blading angles are13" and 24" with a blade velocity of 70m/s. Using the blade velocity vector diagram (Figure 2), a velocity coefficient (K2) of 0.92 and assumptions 1, 2 and 3 calculate: i) The blade efficiency [8 marks] i) The stage efficiency [4 marks] Assumptions for Question 5 part (b): 1) The Kinetic Energy (KE) of steam leaving the last stage is lost. 2) Blading is symmetrical and the mean diameter of all stages is constant 3) For the given blade arrangement assume that U COSa 0.47 tlb U2 L11 lib из Figure 2: Blade velocity vector diagram

Answer 1

:/Vu 10.59 mls work done ee k of steam y 15624 10.55 fepKinetener at the f mozzle peakstm oietlet -efficient ': Nozzle outlet veloci Wozzle inlet veloci Now Noz2le velocity c Nozzle inlet velocittVi step K.E 1321G、128 stage cfticiemen: Nozzle esicienj x blad

v, vi absolute veloc w relative velocit u,meam blade spccd moinj blade N2 absolute Fuid anye at autler wi Velo cit dia goom ÷ 0.32 AVw 0.43 Step Σ w, sine , A,: 22, 45 5t K2 o.92- velocity coefficent W28.22 m/s 1. bC1-73, 55。