Characteristics of the hydrogen jet combustion through multiport injector arrays in a scramjet combustor. (27th December 2018) - Liu, Chaoyang
Abstract: Large eddy simulation of the hydrogen jet combustion in a cavity-stabilized scramjet combustor with three parallel injectors is performed in this study, the emphasis of which is placed on the turbulent flame regime as well as the overall performance analysis. This combustor operates in a scramjet mode with a global equivalence ratio of 0.124, as the chemical heat released is not enough to form thermal chocking. The code framework utilizes an adaptive central-upwind weighted essentially non-oscillatory scheme with a low numerical dissipation to accurately capture turbulent structures in the flowfields, and an assumed probability density function approach to close the terms of the production rate of species. Turbulent fluctuations in the incoming boundary layer are initiated and sustained by a multi-wall recycling/rescaling technique, augmenting the mixing degree of the jet and crossflow. The numerical results show that the large scale vortices between the adjacent jet wakes interfere with each other in the downstream, resulting in a portion of the premixed flame. However, the turbulent diffusion combustion still dominates the whole combustor, occurring in a widespread range of Mach number. And the violent chemical reaction favours a high-temperature environment with a proper scalar dissipation rate. The diameter of multiple jets is smaller in comparison to that of the single injection, so that its penetration height is a little lower under the same spout pressure. Altogether, the parallel injection strategy is beneficial to improve the overall combustor performance, and will not lead to excessive total pressure loss. Highlights: A high-precision LES solver is adopted to study the regime of parallel jet flame. Turbulent diffusion flame governs the combustor in a wide range of Mach number. Reaction favours high-temperature conditions with proper scalar dissipation rate. Parallel injection behaves an obvious advantage in the combustion efficiency.