Dynamic Response to Global Oscillation of Propulsion Systems with Cavitating Pumps

摘要

A time-domain model was developed to evaluate the dynamic response of pumping systems in the acceleratingnenvironment of rockets with a focus on cavitation. The model was first verified by comparing the results withnmeasurements in ground-based tests of an LE-7A rocket engine. In these tests, various resonances occurred andnlevels of pump cavitation or incorporation of an accumulator altered them. Themodel results simulated the test datanwell,matching both the frequency and the amplitude.The test andmodel results also demonstrated the stability of thenLE-7A propulsion system within nonaccelerating environments. Then, the model was used to examine the responsenof the propulsion system in accelerating frames; sinusoidal vehicle oscillations over a range of frequencies werenexplored. Under noncavitating conditions, the pressure amplitudes within the propulsion system did notnsubstantially exceed the quasi-static acceleration head response u0001ah. However, under cavitating conditionsn(u0002 u0001 0:02), the same accelerations produced violent responses with pressure and flow amplitudes about 2 orders ofnmagnitude greater than in noncavitating conditions. The obvious conclusion is that vehicle oscillations can causensubstantial pressure and flow amplitudes, particularly when the pump is cavitating, even if the ground-based testsnand the calculations in static frames indicate stable and well-behaved responses.