An axial-flow compressor is to compress air from 27°C and 1 atm to 5 atm. The mean blade speed is 225 m/s and the stage loading coefficient is 0.4 for all the stages. If the stage efficiency is estimated to be 91%, how many stages are needed? (Taking Cp=1.005 kJ/kg-K and y=1.4) Answer: 10

Combustion gases with k=1.35, Cp =1107 J/(kg.K) and R= 287 J/(kg.K) flow at stagnation pressure and stagnation temperature of 390kPa and 1150 K respectively, flow through a 90o IFR turbine to an exit static pressure of 100 kPa. The total to static efficiency is 80% and the flow leaves the stator choked (Mach Number=1). The relative velocity at the inlet to the rotor is radial and the flow leaves the turbine without a swirl. Find (a) the work delivered per unit flow rate, (b) the impeller tip velocity and (c) the flow angle at the inlet to the rotor.

Consider the same problem in which an axial compressor with a mean diameter of 0.8 m is being designed to run at 3000 rpm. The whirl velocities at the inlet and outlet are 5m/s and 30 m/s, respectively. The air mass flow rate through the compressor is 2 kg/s at a temperature of 27 °C. Assume C, of air equal to 1000 J/kg-K and Cy = 718 J/kg-K. %3D The temperature change is equal to O 3.14 K 5.28 K 7.42 K OOK