Experimental investigation on upstream fuel injection technique of RBCC scramjet mode

Upstream fuel injection in the inlet/isolator is a promising fueling strategy for the reliable operation of rocket-based combined-cycle (RBCC) engine scramjet mode, where fuel must be injected and mixed with the air in an extremely short time. A ground direct-connect test system was used to simulate the condition of incoming air and the combustion in combustor. Experiments have been conducted to investigate the upstream fuel injection of heated/non-heated kerosene at Mach 5.5, and appropriate fuel injection strategy has been proposed according to the result. An observation window was installed at the combustor wall surface to study the flame propagation. The attained results reveal that high combustor pressure and efficient combustion can be achieved by upstream fuel injection coupled with the injection of pylons positioned downstream for non-heated kerosene, while high combustor pressure can be achieved by only upstream fuel injection with heated kerosene. Resident flame can be formed and hold between the central strut base and pylons when the primary rocket is turned off.