MAE 112 PROPULSION MIDQUARTER EXAM February 10, 2010 Do all three problems in one-hundred-and-ten minutes. Books, notes and calculators can be used freely. No computers or communication devices are allowed. If tables or charts are used rather than formulas, identify the source. 1. Consider a rocket nozzle with initial pressure and temperature of thirty atmospheres and 5100 R. The value of = 1.2 and the value of c p = .32 Btu/1bm R. The throat area is 0.5 ft 2 . The flow is underexpanded to 0.3 atmospheres with the ambient pressure of 0.15 atmosphere. Assume 100% polytropic efficiency for the nozzle flow. Calculate: (a) the characteristic velocity c*, (b) nozzle exit velocity U, (c) the mass flow, (d) effective exhaust velocity c, (e) the thrust coefficient, and (f) the thrust. 2. Consider a ramjet in flight at a Mach number of 2.5 with ambient conditions at 270 K and 0.7 atmosphere of pressure. The air capture area in the free stream is 0.25 square meter. The inlet design involves first a wedge that deflects the stream by an angle of 20
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