Investigations into Realistic Shock-Induced Combustion Ramjet Engine Configurations for Hypersonic Propulsion


The focus of our research effort at UTIAS is the systematic study and development of the potential aeropropulsive characteristics of a very high flight Mach number airbreathing propulsion concept, namely, the SHock-induced Combustion RAMJET or SHCRAMJET. The shcramjet concept was born from the difficulties associated with the hypervelocity diffusive burning process taking place in the more commonly know airbreathing scramjet engine. While showing great promise, the scramjet design is hampered by the slow rate of diffusive burning in the combustor at very high flight Mach numbers. This results in a longer combustion chamber than the shcramjet, required to mix adequately the fuel with the incoming air, and release the available energy of the mixture. This translates into a more massive structure of the engine and a more complicated cooling system, which decreases the performance of this type of flight vehicle.

A way out of this dilemma is to decouple the fuel/air mixing and the combustion processes. The premixing of fuel and air can be accomplished in the long slender forebody (inlet) flow of the vehicle, taking care to avoid premature ignition of the premixed flow. Combustion can then be initiated by a conveniently located shock wave, generated by a wedge or blunt body. The ensuing shock-induced combustion is very rapid and results in a very short and lightweight combustor. Considering that for acceleration to orbit missions, such as single-stage-to-orbit launch vehicles, the engine weight is a major concern, the advantage of this particular mode of heat addition to supersonic flow is not insignificant. A schematic of the shcramjet is shown below.

Shcramjet
A schematic of the shock-induced combustion ramjet (shcramjet). It differs from the scramjet by injecting fuel in the inlet and burning the mixture through a conveniently located shock wave.



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