| The flow field in the immediate vicinity of a cantilevered ramp fuel injector is investigated in order to determine whether premature ingition occurs while the fuel/air mixing process is taking place. Two configurations of cantilevered ramp injectors are studied: the "A" configuration injector (with non-zero compression and expansion angles), and the "B" configuration injector (with zero compression angle and non-zero expansion angle). The study was conducted using a laminar, three-dimensional, multispecies flowsolver developed in generalized coordinates to solve the Navier-Stokes equations with hydrogen/air finite rate chemistry. The method consists of an upwind TVD scheme for the discretization of the convective fluxes coupled with a semi-implicit LU-SGS scheme for temporal discretization. The finite-rate chemistry model chosen for the present study includes 9 species (H2, O2, H, O, OH, H2O, HO2, and N2) and 20 reactions. The chemical solver assumes that the nitrogen is inert, which is a valid assumption when the static temperatures do not exceed 3000 K. The analysis of the numerical solutions shows that premature ignition occurs for both configurations considered in the present study. The fuel is ignited by the hot air which is raising from the boundary layers corresponding to the lower wall of the channel that contains the fuel injectors. |
