Chapter 8: 1. (12 Points): The absolute flow at the pitchline to a compressor rotor has a coswirl with C. = 78 m/s. The exit flow from the rotor has a positive swirl, C. =172 ms. The pitchline radius is at r = 0.6 m and the rotor angular speed is a = 5.2.20 rpm. Calculate the specific work at the pitchling and the rotor forque per unit mass flow rate (70). 2. (12 Points): A compressor stage develops a pressure ratio of x=16. Its polytropic efficiency is 6=0.90. Calculate the stage total temperature ratio and compressor stage adiabatic efficiency . Assume 7=14. Use Equation 8.36 to assess your calculation of .. 3. (3 Points): Apply Enler turbine equation (Equation 3.127a) to a streamtube that enters a compressor rotor blade row at 7=2.5ft with zero preswirl and exits the row at r = 1.7 ft and attains 1000 ft/s of swirl velocity in the absolute frame. Assume that the shaft rotational speed is = 5000 rpm. 4. (5 Points): A portion of a compressor map surrounding the design point is shown with Problem 8.40 (Figure PS.40, pg. 646 and below). Calculate this compressor's stall margin. Stall line Design point 24 22 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 N causes 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: 3. (10 Points): The inlet static pressure to an impeller is p, = 100 kPa and its exit static pressure is p. = 200 kPa with inlet relative dynamic pressure q = 140 kPa. Treating the impeller as a diffuser, assuming = 14, calculate (See Example 9.3): a. Inlet relative Mach number, M. b. Static pressure recovery coefficient, Cre 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.