The effects of isolator length on combustion in a scramjet engine model

The simulations of supersonic combustion of hydrogen-air in a model scramjet engine combustor have been carried out in this study to investigate the effects of the length of the isolator that is prepended to the combustor. For the short isolator, 0 ≤ x′ ≤ 6.5, where x′ is the nondimensional longitudinal length, with the combustor cavity depth of H = 20 cm used as the length scale for nondimensionalization. For the long isolator, −6. 5 ≤ x′ ≤ 6. 5. In both cases, the injection is located at x^′ = 0. 7. The results obtained are significantly different for the two cases. The dynamics is dominated by the extensive amount of backflow in the extended isolator case, with several recirculation zones upstream of the injection location, compared to just one in the case of the shorter isolator. Boundary layer development in the longer isolator leads to very strong backpressure dynamics and flow separations that serve to move the hydrogen far upstream, hold the flame, and lead to an extensive upstream region of combustion.