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Unformatted text preview: MEAM 203 SPRING 2007 THERMO - MIDTERM II Closed books. One sheet with formulas is allowed. Answer all three questions. Write clearly! Explain all steps! GOOD LUCK. diffuser (45%) 1. A new aircraft is designed to fly with steady state velocity of 260m/s at an altitude of 8000m, where the ambient air pressure and temperature are, respectively, 35kPa and 236K. The aircraft designer would like to equip the aircraft with Ramjet engines. If you happened to miss class, here are a few quick details. It is convenient to carry out the analysis using a frame of reference that is moving with the aircraft. In the ramjet engine, the air is compressed in the diffuser. The air exits the diffuser with very low velocity to be mixed with fuel, combusted, and expanded in the nozzle to provide thrust. Assume the air to be an ideal gas ( R=0.287kJ/kg-K ) with temperature-independent specific heat Cp=1kJ/kg-K and k=1.4 . In your calculations, neglect the mass of the fuel, and carry out all the calculations for 1kg of working fluid. (i) (5%) Assume that the diffuser is reversible and adiabatic. Determine the pressure ratio in the diffuser. (ii) (5%) 630kJ of heat per kg of air are added in the adiabatic combustor. What is the temperature of the air at the nozzles inlet?...
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