Reaction and Mixing-Controlled Combustion in Scramjet Engines

Abstract

H2-fueled scramjet engines were tested under Mach 4 (M4) to Mach 8 (M8) e ight conditions, and the local equivalenceratio andcombustion efe ciency weremeasured by gassampling attheengineexit.Correlationbetween the local values of equivalence ratio and combustion efe ciency showed that the M4 combustion was principally reaction controlled and the reaction and the mixing-controlled combustion coexisted in the M6 condition. The M8 combustion in the engines was rate controlled by the mixing of H 2. Comparison of engine performance in the air, supplied by a combustion heater and a storage heater, indicated that the performance strongly depended on the air-heating methods. The dependence of engine performance on air-heating methods could be explained by the e nding that the M6 engine combustion was partially reaction controlled. The wall-heating rate and pressure distribution in the M6 tests also supported the shift from the partially reaction-controlled to the mixing-controlled combustion as the fuel rate was increased. The mixing-controlled combustion suggested weak facility dependence intheM8 condition.Becausereaction in the M8 condition is notsufe ciently fast, the main combustion region might be blown downstream in the engine.