Fluid-hammer induced pressure oscillations in a cryogenic feed line

Abstract

A transient, thermodynamic flow model is developed to simulate pressure oscillations in cryogenic fluid occurring due to sudden closing of valves, a phenomenon commonly known as fluid-hammering. The effects of line dimensions and flow rate changes on amplitude and frequency of these oscillations are investigated using numerical analysis. The model is validated with in-house experimental data and literature based on MOC solution for fluid-hammer. Current study is significant for understanding pressure oscillations during valve operation in launch vehicle cryogenic engine. Very low pressures caused due to fluid-hammer could lead to reduction in pump inlet pressure below saturation level, resulting in pump cavitation. Pressure oscillations also cause fluctuations in propellant flow rate, resulting in undesirable variations in thrust output from the engine. Computational analysis shows that increase in line diameter and reduction in the rate of change of flow rate reduce the peak amplitude of pressure oscillations.