Investigation of pressure oscillations in regenerative liquid propellant guns

Pressure oscillations are often observed in regenerative liquid propellant guns (RLPGs). They originate during combustion and travel through the gun chamber and down the gun tube. Analyses of data from medium and large caliber gun firings reveal that the dominant frequencies can vary from a few kHz to about 60 kHz. The frequency depends, at least in part, on chamber dimensions, suggesting the pressure variations are reinforced by wave reflections forming acoustic types of oscillations. Some frequencies may depend on the dimensions of the injector ports and possibly mechanical vibration of system components. They may further depend on complex flow interactions between the injected propellant and the ajdacent high temperature combustion gases. Approaches to mitigate the effect of pressure oscillations include measures to alter the mass burning rate of the propellant and various damping techniques such as cavities and liners. This paper examines the sources of pressure oscillations, vario us diagnostic tests for studying pressure oscillations, and reduction methods. The analyses are based on results of different types of injectors used in RLPGs and recent numerical computational studies.