Influence of fuel injection position and equivalent mixture ratio on chemical non-equilibrium effects of single expansion ramp nozzle

Chemical non-equilibrium flow was investigated for the scramjet single expansion ramp nozzle (SERN) with a strut-based liquid-kerosene-fueled combustor. Two-dimensional Reynolds-averaged Navier-Stokes(RANS) equations were solved with the species conservation equation for continuous phase and the renormalization group(RNG) k-ε turbulence model. Lagrangian discrete-phase model was analyzed for liquid-kerosene droplets behavior in the supersonic stream. Combustion was simulated by kerosene surrogate fuel's 10-species and 13-step reduced reaction kinetics mechanism with use of Arrhenius's laminar finite rate model. Parametric studies were carried out to estimate the influence of different fuel injection positions and equivalent mixture ratios on the SERN chemical non-equilibrium effects. Numerical calculation results show that the strut-based combustor enables convenient modeling of various SERN entry conditions, which is similar with many preceding investigations, by changing the injector strut position and controlling the mass flow rate of each injector. Chemical non-equilibrium effects function in the whole SERN, especially in the initial flow expansion region, leads to obviously higher SERN performance of the non-equilibrium flow than that of the frozen flow. Furthermore, the distributed fuel injection pattern plays a significant role in enhancing the combustion efficiency in combustor, but weakening the chemical non-equilibrium effects funciton in SERN. Additionally, while the equivalent mixture ratio increases, the SERN thrust coefficient and lift coefficient rise gradually, and the increment of non-equilibrium flow in relation to frozen flow becomes higher as well. To be specific, the equivalent mixture ratio is 0.6, the maximum increment of thrust coefficient and lift coefficient are 11.6% and 25% respectively.