2 Chapter 8: 1. (12 Points): The absolute flow at the pitch line to a compressor rotor has a cosid with G = The exit flow from the rotor has a positive swirl, C=172 m/s. The pitch line radius is at 7=46 m and the rotor angular speed is o=5220 rpm Calculate the specific work at the pitch line and the rotor torque per unit mass flow rate (m/m). 2. (12 Points): A compressor stage develops a pressure ratio of x, = 16. Its polytropic efficiency is &=90. Calculate the stage total temperature ratio and compressor stage adiabatic efficiency, Assume = 14 Use Equation 8.36 to assess your calculation of . 3. (5 Points): Apply the Enler turbine equation (Equation 3.127a) to a stream tube that enters a compressor rotor blade now str = 2.5t with zero pre-swirl and exits the row at r=27 and attains 1000's of swirl velocity in the absolute frame. Assume that the shaft rotational speed is w = 5000 rpm. I 4. (5 Points): A portion of a compressor map surrounding the design paint is shown (Figure below). Calculate this compressor's stall margin. 22 24 22 Design point 80 82 Corrected mass flow rate in kg/s 5. (12 Points): Describe the phenomenon of a stall in an aircraft compressor, including the flight characteristics that contribute to the stall. Be sure to discuss the definitions and couses of flutter and buffet. If the stall continues, how can this influence flow in the combustor? 6. (8 Points): Regarding flow diffusion in a compressor, discuss the definition of a stage-based figure of merit. What does this figure tell us? What is an optimal degree of reaction and why? 7. (8 Points): Why are axial flow compressors preferred over centrifugal compressors for large turbojet engines? Chapter 9: 8. (10 Points): The inlet static pressure to an impeller is pr = 100 kPa and its exit static pressure is ps=200 kPu with inlet relative dynamic pressure q = 140 kPa. Treating the impeller as a diffuser, assuming y=1.4, calculate: a. Inlet relative Mach number, M b. Static pressure recovery coefficient, Cra 9. (12 Points): Discuss the three types of centrifugal compressor impeller geometries and provide an example of an engine using a centrifugal compressor with each type 10. (10 Points): Discuss the main purpose of the inducer and radial diffuser in a centrifugal- flow compressor.