Effects of self-throttling on combustion enhancement in supersonic flow with transverse injection

• A new approach is proposed to enhance the supersonic combustion.
• The proposed method has been validated using numerical methods.
• Compressibility modification is introduced to RANS turbulence model and predictions are improved significantly.
• The complex jet-to-crossflow flow structures are well predicted by the present numerical method.

Efficient fuel/air mixing and combustion are difficult to achieve in supersonic flows. Transverse fuel injection from combustor walls is commonly used in Scramjet (supersonic combustion ramjet) design. The present study proposes an approach to enhance supersonic combustion under those conditions. Based on the specific jet-to-crossflow flow structures, it is proposed to connect the upstream region and downstream region of fuel injection slot through a channel. The higher pressure upstream of the slot drives part of the fluid flow into downstream regions and a self-throttling is established. Numerical method is used to validate the concept for a model combustor applying RANS (Reynolds-Averaged Navier–Stokes) approach. A compressibility modification k−εk−ε turbulence model is used which combines the dilatational compressibility effect and shock unsteadiness effect. The modified turbulence model is found to be able to capture the complex flow structures with good accuracy. Five operating conditions of jet-to-crossflow pressure ratio are studied for both nonreactive and reactive flows. The results show that the self-throttling changes the flow fields a lot, and affects the separation region and interactions of the reflection shock with mixing layers downstream the injection slot. Its effects on mixing and combustion efficiency are analysed for five different cases. The results demonstrate that self-throttling approach can increase the combustion efficiency with relative low injection pressure where the reflection shock goes downstream the injection slot. At the same time, more total pressure loss is observed. The combustion enhancement is more significant with relative low injection pressure. The self-throttling method has potentials for further studies.