Abstract
The successful operation of the scramjet engine considerably relies on the mixing performance of the fuel and air in the combustor where fuel has short residence time to mix with the supersonic air stream. This article investigates the impacts of orifice shape on the mixing mechanism of fuel jets into the supersonic air stream of Mach=4. Circulation factor, penetration, and mixing efficiency of three types of lobe injector (2-lobe, 3-lobe, and 4-lobe) are broadly compared to achieve an optimum model for injector type. Computational fluid dynamic is considered for the modeling of these three lobe-injectors at a high-speed air stream. The mechanism of fuel mixing and duel distribution is fully discussed and the main effective terms are introduced. Our results show that the formation of the upstream circulation would result in the horseshoe vortex which improves fuel penetration in the depth of the domain. The comparison of mixing performance of these orifices shows that the mixing efficiency of the 3-lobe is about 25% more than that of the 2-lobe and 4-lobe.