Evaluation of internal aerodynamic performance in scramjet engines

Aerodynamic performance of scramjet engines was measured by using 1/5-subscaled (0.42 m-long) models of H 2-fueled scramjet engines. The air capture ratio, the drag and the wall pressure distributions in the engines were measured using the models. By considering the momentum balance between the inlet and the nozzle, the internal drag of engines were expressed with the air capture ratio, pressure recovery factor and the total temperature ratio. To evaluate the pressure recovery based on the engine drag, the total pressure loss was analytically estimated as the sum of pressure losses for oblique shock and friction in the inlets. The friction loss in engine internal flow was evaluated by one-dimension al analysis of duct flow with changes in the cross-sectional area and total temperature. It was found that the pressure recovery across the engine was about 6Q% in the Mach 4 engine without struts and 19% in the Mach 6 engine with a small strut. With a larger strut, the pressure recovery was reduced to about 10% in the Mach 6 condition. This evaluation of the pressure recovery enabled calculation of the flow condition at the entrance of the combustor for evaluation of the engine performance in mixing-controlled or reactioncontrolled combustion. Nomenclature