Overview of Fuel Injection Techniques for Scramjet Engines

Abstract

As one of the most promising hypersonic propulsion systems for hypersonic vehicles, the scramjet engine has drawn an ever increasing attention of researchers worldwide. At present, one of the most important issues to be dealt with is how to improve the fuel penetration and mixing efficiency and make the flame stable in supersonic flows. Further, how to reduce the structural weight of the engines is an urgent issue that needs to be considered. The ongoing research efforts on fuel injection techniques in the scramjet engine are described, mainly the cavity flame holder, the backward facing step, the strut injection and the cantilevered ramp injection, and the flow field characteristics and research efforts related to these fuel injection techniques are summarized and compared. Finally, a promising fuel injection technique is discussed, namely a combination of different injection techniques, and the combination of the cantilevered ramp injector and the cavity flame holder is proposed. This is because it can not only stabilize the flame, but also shorten the length of the combustor, thus lighten the weight of the scramjet engines.