Scaling trajectories for jets in confined cross-flows

Abstract

In a non-premixed flame, the mixing of fuel emerging from a jet burner with quiescent air plays a dominant role in the combustion process. The use of radial injectors upstream of the nozzle exit can be used to increase boundary layer turbulence, and thereby enhancing the mixing of fuel and air. In the current paper, a single side jet entering radially into a pipe is investigated experimentally using planar laser induced fluorescence (PLIF). This configuration is variant of a jet in cross-flow (JICF), although the cross-flow generated by the central pipe is confined cross-flow. Therefore, the walls of the pipe may influence the side-jet and the existing knowing of JICF may not extend completely to the confined cross-flow environment. In the current paper the penetration of a side jet into the pipe flow is assessed and a new scaling parameter is determined. Scaling the depth by r0.75D, where r is the velocity ratio and D is the central pipe diameter, is proposed and compared with conventional scaling for JICF (rD and r2D). The results indicate the proposed scaling produces in a very good collapse of data onto a single line for non-laminar side jet emerging into turbulent flows.