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Question: compressible flow 2 consider a rocket engine with a convergentdivergent...

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Compressible flow 2 Consider a rocket engine with a convergent-divergent cross-section. The nozzle is fed from a combustion chamber which acts as a reservoir where the stagnation pressure and stagnation temperature are 10 MPa and 1000 K, respectively. The divergent passage discharges into a downstream chamber connected to an evacuation pump and valve, where the back pressure can be varied between 10 MPa and vacuum. The throat and exit areas are 0.1 m2 and 0.4 m2 respectively. (a) Calculate the range of back pressures in the downstream chamber which create the (i) subsonic; (ii) non-isentropic; (iii) over-expansion; and (iv) under-expansion flow regimes. Assume that the working fluid is calorically-perfect air (i.e., constant specific heats at all temperatures) and that the flow, apart from the existence of shock waves, is isentropic throughout the nozzle. [15 marks] (b) Sketch, qualitatively, the exhaust-flow patterns for the over-expansion [5 marks] (c) Estimate the mass flow rate through the nozzle for the case where the [5 marks] and under-expansion flow regimes, and discuss salient features. back pressure is a vacuum.

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