Numerical Investigation of Multi-element Vitiated-air Heater for Scramjet Testing

摘要

The scramjet experiment relies on combustion air pre-heaters to provide flight enthalpy simulation. The one-element heater has disadvantages of non-uniform flowfield at the exit plane and high temperature on the injection faceplate. In this paper, a mul-ti-element heater (with seven coaxial injectors) was designed. Numerical simulation of the three-dimensional reacting flow in multi-element heater had been carried out. The two-equation shear stress transport κ-ω turbulence model was used for modeling turbulence and eight-step finite-rate mechanism was used for modeling the H2/Air chemical kinetics. The results show that: (1) the uniformity of exit flowfield is improved significantly by using multi-element coaxial injectors, the temperature non-uniformity coefficient is decreased from 21% to 8%, oxygen mole-fraction non-uniformity coefficient is decreased from 17% to 1.4%; (2) the heat load of injection faceplate is improved, the highest wall temperature is 650k when L/R=0.65. The heater could operate for long time test without adding cooling system for the faceplate.