Implication of diamond shaped dual strut on combustion characteristics in a cavity-based scramjet combustor

The present study deals with the implication of the novel diamond-shaped dual strut with a backward-facing step on the combustion characteristics of a cavity-based scramjet combustor. The dual strut with diamond shape is considered for the investigation since it triggers the flow separation leading to the disturbances in the flow especially at the top and bottom wall thus serving the flame holding purpose. Firstly, the combustion characteristics of a combustor with a single strut are compared and evaluated with a dual strut based combustor to portray the effect of a dual strut. A separate study is carried out to investigate the influence of spacing in a dual strut on the performance of the scramjet combustor. Our study reveals that the dual strut with a cavity greatly affects the formation of vortices, separation region, and recirculation region which is evident from an increase in the mixing and combustion efficiency. It can be observed that the formation of vorticity and the recirculation region is found to be larger due to the strong and multiple reflections of a shock in the case of the diamond-shaped dual strut with a backward-facing step injection as compared to the single diamond-shaped strut. Further, it is observed that the spacing(D) in the dual strut also affects the mixing and combustion performance. It is found that the value of mixing and combustion efficiency decreases with an increase in spacing independent of Mach number due to the presence of larger separation regions. It can also be observed that the length of the recirculation region occupies entire the cavity making flame stable when the spacing is the least. This is desirable as far as engine performance is concerned. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.