Combustion Dynamics and Stability of a Fuel-Rich Gas Generator

摘要

The dynamic characteristics of fuel-rich combustion have been studied using an experimental combustornsimulating a gas generator for a liquid rocket engine. The combustor burns liquid oxygen and fuel (Jet A-1) at anmixture ratio of about 0.32 and a chamber pressure ranging from 4.10 to 7.24 MPa, which covers subcritical tonsupercritical pressures of oxygen. For the investigation of combustion dynamics, pressure fluctuation measurementsnusing piezoelectric sensors have been a major probe throughout the present study. Two different types of injectornheads equipped with biliquid swirl coaxial injectors and either a short nozzle or a turbine manifold nozzle have beennused in the study. Fuel-rich combustion of both injector heads with the short nozzle revealed pressure pulsation atnfrequencies of about 128 Hz, which attenuates along with an increase of a chamber pressure. Combustion tests withnthe turbine manifold nozzle conducted at chamber pressures lower than the oxygen critical pressure showedncombustion instabilities at a frequency of 330 Hz, which has been identified as a longitudinal resonant mode by anlinear acoustic analysis. The combustion instabilities seem to be induced by inherent pressure fluctuations from thenbiliquid swirl coaxial injector when the chamber pressure is below the oxygen critical pressure.