Influence of main flow inlet configuration on mixing and flame holding in transverse injection into supersonic airstream

摘要

A numerical study on mixing and combustion of hydrogen transversely injected into a main airstream is performed, by solving two-dimensional full Navier-Stokes equations. The focus of this paper is to study the means of increasing the mixing and combustion efficiencies, and the flameholding capability for supersonic propulsion application by changing the main flow inlet configuration. Accordingly, the following three inlet configurations are considered: (1) A finite parallel flow with backward-facing step; when the main flow enters through a finite-width inlet of wall, the wall under the inlet acts as a backward-facing step. (2) A finite parallel flow without step; although the inlet configuration is identical to Case 1, there is no step under the inlet. (3) The infinite parallel flow; the main flow enters throughout the left boundary. As combustion modeling we have sued full chemistry between hydrogen and air consisting of eight species (H_2, O_2 H, O, OH, H_2O_, HO_2, H_2O_2) and 19 reactions shown in Table 1. The effects of inlet configurations are evaluated by calculating mixing and combustion efficiencies. The results show that a finite parallel flow with backward-facing step (Case 1) causes the highest penetration and mixing of hydrogen and provides the best flameholding region between the downstream injecting slit and backward-facing step. The effects of high penetration and mixing on combustion, and characteristics of the reacting flowfields are studied. The finite parallel flow configuration (Cases 1 and 2) makes the bow shock steeper and eventually increases the di