Experimental Investigation of an Alternative Rocket Configuration for Rocket-Based Combined Cycle Engines

Experimental tests are conducted to evaluate two rocket exhaust configurations within an Rocket-Based Combined Cycle engine model. Each configuration uses a single rocket chamber but expands the rocket exhaust to a different geometry. One configuration uses two traditional circular rocket nozzles whereas the other uses two annular exhaust geometries based on the Exchange Inlet design. Wall pressure data are collected along the length of each configuration to evaluate the air entrainment. The annular configuration is shown to increase the entrainment ratio by as much as 28% over the traditional circular rocket design. The annular configuration is also shown to choke the incoming airflow at a lower rocket chamber pressure more uniformly across the engine cross section. Total pressure measurements are also obtained at the engine exit plane, which show that the annular configuration yields an average Mach number 57% higher than the circular configuration under conditions close to those for maximum air entrain...