Propulsion exam questions, Assignments of Aerospace Engineering

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FINAL - QUESTION 1 A separate-stream turbofan engine flies at M=0.8 at an ambient temperature of 216.7 K and ambient pressure of 21.4 kPa. LPC and HPC total pressure ratios are 2.5 and 12, respectively. Turbine inlet total temperature is 1700 K, and bypass ratio is 8. 2% of total pressure is lost due to friction at the diffuser. Maintaining the same altitude and the same throttle setting, this aircraft accelerates to Mach 0.9. As a result, its bypass ratio increases to 8.5, total mass flow intake increases by 5%, and HPC total pressure ratio becomes 11. Gamma_c=1.4, compressor isentropic efficiencies: both 95%. a) Calculate the ratio of the new to original rotational speed (N/NR) of the HP spool. b) If the new total mass flow rate is 250 kg/s, calculate the new corrected mass flow rate. TO RECEIVE FULL CREDIT: State your equations and show your calculation steps in detail by plugging in your numbers. State your assumptions clearly. Keep two digits after the decimal point to avoid round-off errors. Use the same station numbering we use in lectures.