Pressure Oscillations in Liquid-Fueled Ramjet Engines

Citation

Yang, Vigor (1984) Pressure Oscillations in Liquid-Fueled Ramjet Engines. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/rfpg-es59. https://resolver.caltech.edu/CaltechETD:etd-09052006-153951

Abstract

Pressure oscillations in liquid-fueled ramjet engines have been studied both analytically and numerically within the low frequency range. We examine first the linear unsteady motions in coaxial-dump configurations. The flowfield in the dump combustor is approximated by division into three parts: a flow of reactants, a region containing combustion products, and a recirculation zone, separated by two infinitesimally thin sheets: the flame and the vortex sheets. The three zones are matched at these sheets by taking into account kinematic and conservation relations. The oscillatory field in the inlet is coupled to the field in the combustor at the dump plane to determine the complex frequencies characterizing the linear stability of the engine. Favorable comparison with the experimental data obtained at the California Institute of Technology has been obtained.

Numerical analysis has been applied to investigate the nonlinear behavior of the shock wave in the inlet diffuser. Both viscous effects and the influences of injecting fuel/air mixture are accounted for. The response of a shock wave to various disturbances, including finite and large amplitude oscillations, has been studied in detail. The results obtained serve as a basis for analyzing the stability characteristics of the inlet flow.

Numerical calculations have also been conducted for the pressure oscillations in side-dump ramjet engines. The flowfields have been constructed in two regions: the inlet section, including a region of fuel injection, and a dump combustor. Each region is treated separately and matched with the other at the dump plane. Following the calculation of the mean flowfield, the oscillatory characteristics of the engine are determined by its response to a disturbance imposed on the mean flow. Results for the frequencies and mode shapes have shown good agreement with the experimental data reported by the Naval Weapons Center, China Lake.

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