Assessment on the supersonic combustor performance induced by the asymmetric struts with hydrogen fuel

Abstract

Enhancing the combustion efficiency of gas fuel, i.e., hydrogen, in supersonic reacting flows has attracted wide attention around the world, besides, the flame holders are the key components of scramjet engines which even can make the injected fuel and local air mix and burn better in milliseconds. In previous researches, two struts with backward facing-steps have been proved to be a superior flame holder, also, some parameters of the two struts have been studied in detail. In this work, an in-house code was developed to compute the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the SST k−ω turbulence model and the one-step reaction finite-rate/eddy-dissipation model, next, the effects of the horizontal staggered distances of the two struts have been investigated computationally including with/without chemical reactions. The results indicate that the structure of the flow field behaves comparably, also, the distributions of the mixing efficiencies, including mixing length, show little differences for all the cases with distinct staggered (horizontal) distances, i.e., the cases of upper and lower struts staggered, in the cold flows. However, there are considerable discrepancies for the total pressure losses, and the symmetric struts case is the minimal one. In the reactive flows, the flow field including the section in the vicinity of the fuel injectors, combustion efficiency and total pressure loss vary obviously for the cases lower strut staggered, here, the case of the staggered distance, which equals 2 mm, has the greatest combustion efficiency at the outlet of the combustion chamber. Whereas the total pressure loss at the outlet of the combustor for the symmetric struts case, which's staggered distance equals 0, is minimal. Next, the flow field and total pressure loss for the cases of upper strut staggered show considerable discrepancies, also, the symmetric case has the lowest total pressure loss. Whilst the combustion efficiency behaves comparably, except in the vicinity of the injection position. Note that, the asymmetric struts benefit the combustion of the fuels with extra pressure loss cost. For high combustion efficiency with the total pressure loss acceptable, the case sd-l = 2 mm is the optimal scheme.