Combustion efficiency of a porous injector during throttling of a LOx/H₂ combustion chamber

German Aerospace Center (DLR) Institute of Space Propulsion Langer Grund Hardthausen 74239, Germany

Abstract

The effect of throttling on combustion efficiency and stability of a porous injector head has been investigated for the LOx/H₂ propellant combination. Several pressure ramps (PR) ranging from 30 to 100 bar have been used so that a broad range of possible chamber pressures was covered. Regarding the design pressure of 80 bar, this was equivalent to a throttling range of 37.5% to 125%. The hydrogen injection temperature was varied between 50 and 105 K. The oxygen injection temperature was about 115 ± 5 K. All tests were performed at the P8 test bench using a 50-millimeter diameter modular combustion chamber. The combustion efficiency at a hydrogen injection temperature of 105 K varied between 97.5% and 99% and was nearly independent of pressure. For hydrogen at 50 K, the combustion efficiency increased with chamber pressure and ranged from 94% to 97%. The combustion roughness at 50 K was higher than for the 105-kelvin test cases.