Influence of coaxial injector element design on heat transfer in oxidizer rich staged combustion cycle engines

Every effort to develop new engines for future launcher propulsion has to address the design of injector elements, as it not only determines the combustion performance but is also a crucial factor influencing the heat transfer to regeneratively cooled walls and the combustion stability. Therefore, the Institute of Flight Propulsion at the Technische Universität München and ASTRIUM Space Transportation, Ottobrunn, investigate the impact of injector design for oxidizer rich staged combustion cycle engines on performance, heat flux to the cooling channels and combustion stability. The experiments were conducted on a laboratory level in a single element rocket combustor using gaseous oxygen and kerosene Jet A-I at chamber pressures between 40 bar and 80 bar and mixture ratios from 2.3 to 3.8. Two gas-liquid injector types were used in hot fire tests: a premix injector which injects fuel radially into the core gas stream and a coax-swirl injector. For both the design was varied by changing several key parameters, i.e. injection angle, recess length, number of injection orifices and more. An injector type swirling both propellants - liquid fuel as well as gaseous oxidizer was examined showing high impact on the performance and the heat flux distribution. Aim of this paper is to give an overview over the obtained data for the design variations of the coax-swirl injector.