Supersonic combustion and flame stabilization of coflow ethylene and air with splitter plate

A numerical investigation of supersonic combustion for ethylene and air coflow with a splitter plate is presented, mimicking the flame stabilization and combustion establishment in a dual-combustion ramjet engine. Emphasis is placed on the detailed flow and flame characteristics immediately downstream of the splitter plate and in the shockwave/shear-layer interaction regions. Three different splitter-plate thicknesses, 2, 4, and 8 mm, are considered, to identify the significance of the geometric parameters. The analysis is based on the Favre-averaged conservation equations for compressible chemically reacting flows. Turbulence closure is achieved using Menter's shear-stress transport model with a detached-eddy-simulation extension. Chemical reactions are modeled using a nine-species, ten-step laminar chemistry model with sufficient numerical resolution. Various mechanisms dictating the flame anchoring and spreading properties are examined. The hot stream from the ethylene preoxidization in the gas generator is found to behave like an underexpanded supersonic jet. Its subsequent expansion in the present wallconfined environment has a strong influence on the near-field mixing and combustion. Depending on the splitter-plate thickness, the wake region behind the splitter plate changes in size, and the autoignited flame can be either attached to or detached from the rim. The majority of chemical reactions take place in the mixing layer farther downstream, and the combustion efficiency varies in accordance with the near-field phenomena.