Experimental study on combustion stability and performance of rocket ejector-ramjet engine

The rocket ejector has great potential for bridging the thrust gap between the turbine and ramjet modes of the Turbine-Based Combined Cycle (TBCC) engine. In this work, a rocket ejector was proposed and used in the Ejector-Ramjet (ERJ) engine model. Furthermore, the thrust and thermal-fatigue performances of the rocket ejector are investigated through the thrust bench tests. The combustion stability and performance of ERJ engine are studied by the ground direct-connect experiments under different conditions. Experimental results suggest that the rocket ejector can realize a wide range of thrust variation from 510 N to 1100 N and a specific impulse of more than 250 s, whereas accompanying with a short lifespan about 4 s. As expected, the rocket ejector can significantly expand the flight envelope of the ERJ engine downward to Mach number Ma_∞ = 2.0 and altitude H = 13 km. Nevertheless, when Ma_∞ is less than or equal to 3.0, the ramjet combustor is unable individually operated and that need to be improved for engineering application. The lower oxygen/kerosene ratio of rocket ejector and the equalized injection-forward and injection-center of ramjet fuel are beneficial for enhancing the combustion stability and thrust performance of ERJ engine. Overall, experiments primarily validated that the rocket ejector has the advantages of facilitating ignition and flame stabilization, improving the working environment of the ERJ engine, and expanding the operating range. But the remarkable thing is that both the ejector and ramjet combustor can be greatly improved for optimizing the performance of ERJ engine further.