Rocket-augmented flame stabilization and combustion in a cavity-based scramjet

The scramjet engine has become an important propulsion system in hypersonic vehicles for its high specific impulse, but it also has obvious shortcomings, such as narrow reliable operating and thrust adjustment range, and consequently, insufficient maneuverability. To solve these problems, a rocket is introduced into the scramjet to improve the thrust performance while stabilizing flame and enhancing combustion, referring to the operating principle of the RBCC engine. The function mechanism of the high mass flow rate rocket jet on the flame stability and combustion characteristics in a cavity-based scramjet combustor is investigated through the ground direct-connect test. The experimental results show that: 1) Effective secondary fuel combustion enhancement and thrust enhancement can be obtained through the rocket augmentation. The embedded rocket leads to a 69% increase in the peak combustion pressure. 2) In the rocket-augmented combustion mode, the core combustion zone concentrates in the central region of the flow passage and simultaneously expands upstream, resulting from the increased mixing efficiency of kerosene/air and a more stable flame, which effectively augments the combustion and the engine thrust. 3) As the kerosene injection positions move upstream to the exit of the rocket nozzle, the secondary combustion efficiency can be further improved by inhibiting the negative effects of oxygen consumption by the fuel-rich rocket jet. The length of the high combustion pressure region is increased by 150%, and the scramjet performance has been enhanced significantly. 4) During the process of the kerosene injection position transition, the flame in the combustor keeps sustained under the function of the embedded rocket jet, and the rocket-augmented combustion exhibits favorable robustness. (c) 2023 Elsevier Masson SAS. All rights reserved.