Flow and Heat Transfer of Hydrocarbon Fuel in a Channel with Staggered-Side-Gap Micro Ribs

SCRamjet is exposed to severe thermal environments during hypersonic flights, which poses a serious challenge to the engine cooling technology. Regenerative cooling with hydrocarbon fuel is considered promising, in which the hydrocarbon fuel flows through micro channels (200 µm–3 mm) to absorb the combustion heat release. With strictly limited hydrocarbon fuel onboard, heat transfer deterioration and over-temperature are highly possible. In this paper, micro ribs with staggered side gaps are introduced and numerically studied to enhance the heat transfer. Compared with the straight channel and channel with straight micro ribs, the staggered side gaps alleviate the local low velocity zone and intensify the longitudinal and transverse vortexes. The heat transfer is obviously enhanced. Larger rib height enhances the heat transfer by stronger side gap effects at the cost of larger pressure loss. The best overall heat transfer factor η is achieved in the case of h_rib/H=0.1, which increases by 204.5% comparing to the straight channel. When the rib interval is too small or too large, it approaches to the straight channel. The best overall heat transfer factor η is achieved in the case of L/p_rib=100, which increases by 212.9% comparing to the straight channel. It is known the improvement in the geometry of the ribs, i.e., the staggered-side-gap micro ribs, induces extra transverse vortex and improves the heat transfer performance more effectively. The research of this paper provides support for the cooling design of the SCRamjet.