Effect of strut profile, angled injection, and blunting of leading edge on mixing of supersonic hydrogen-air streams

Abstract

Mixing fuel and air in a scramjet combustor is one of the key challenges in its development due to the short residence time available. Strut based injection is considered a viable alternative and is widely investigated. In the present work, the effect of the strut profile, angled injection of fuel, and the blunting of the leading edge of the strut on the mixing of fuel and air is studied using the Finite Volume Method (FVM). The base case chosen is an experiment with Hydrogen fuel injection from a strut at Mach 2.3 in a supersonic air stream of Mach 2. The popular strut profiles of diamond and wedge shapes are considered. The mixing due to wedge strut with dual injection from the trailing face and the effect of the inclination angle of the two fuels is studied. It is observed that the wedge strut with single fuel injection results in the highest mixing efficiency. Compared to the diamond strut, the distance to reach the complete mixing of fuel and air is reduced by 100 mm for the wedge strut with single injection. The high thermal load on the leading edge of the strut requires blunting (and rounding) for heat removal, and its effect is also investigated. The blunting of the leading edge of the strut leads to a decrease in mixing efficiency and an increase in total pressure loss as well as rise in entropy compared to a strut with pointed leading edge. Blunted wedge strut with single injection requires 40 mm more length for complete mixing than wedge strut with pointed leading edge. Also, after blunting, its rounding increases the mixing efficiency slightly but reduces the total pressure loss and entropy rise noticeably.