Combustion Dynamics of Swirl Coaxial Injectors in Fuel-Rich Combustion

An experimental study was carried out to investigate the combustion characteristics of liquid-liquid swirl coaxial injectors in a fuel-rich gas generator. Propellants of liquid oxygen and kerosene (jet A-1) were burned in a range of mixture ratios (0.29~0.38) and chamber pressures (53.6~57.9 bar) in several combustion chambers with different diameters and lengths. An injector head had 37 identical swirl coaxial injectors with large recess lengths and internal-mixing characteristics. The injector head was connected to combustion chambers and a choked nozzle either with or without an extension pipe. It was found that the combustion characteristic velocity, combustion gas temperature, and combustion dynamics were seldom influenced by the increase of injector recess length in the present fuel-rich conditions. The results of dynamic pressure data and swirl-injector dynamics suggest that the longitudinal-mode combustion instability in the fuel-rich gas generator equipped with biswirl coaxial injectors could be significantly affected by the relationship between the resonant frequency in the combustion chamber and the flow dynamics of the swirl injector.