COMBUSTION STABILITY CHARACTERISTICS OF A SUB-SCALE LOX/LNG ROCKET THRUST CHAMBER

Abstract

The LUMEN project at the DLR Institute of Space Propulsion has the goal of producing a breadboard demonstrator engine powered by LOX/LNG. This paper describes the results of the first hot-fire tests of the shear coaxial injector. A preliminary analysis of the combustion stability characteristics during steady-state operating conditions is presented. All targeted operating conditions were achieved without the occurrence of acoustic instabilities. The conditions for injection-coupled combustion instabilities were avoided. The first tangential mode frequency was observed to increase significantly for low pressure operating conditions, which suggests a drastic change to the distribution of combustion in the chamber. Some combustion roughness can be associated with the phase transition of oxygen during the ignition transient, and strong, low frequency instabilities occurred during an initial operational phase. Notwithstanding these phenomena, the injector satisfies the combustion stability requirements of the LUMEN project.