The influence of a plasma actuator embedded in a bluff-body on the stabilization of nonpremixed jet flames

This study is to experimentally investigate the influence of an annular plasma actuator embedded in a bluff body burner on flame stabilization, extending the previous work on non-reacting jets to propane jet diffusion flames. The objective of the actuator is to produce a vortex ring in the vicinity of the jet exit, subsequently to alter the local flow velocity, and thus to achieve flame stabilization. Results show that repetitive flame reattachment may occur with the presence of the induced vortex ring. Flame reattachment frequency and attachment time are analyzed with fast Fourier transform (FFT) and a probability density function (PDF), respectively, and both results suggest that the degree of interaction between the flame and the vortex ring has strong dependence on the imposed flow momentum, characterized by the momentum ratio of the vortex ring to the main jet. A flame describing function (FDF), characterizing the dynamic flame response to the induced flow, exhibits a trough where the vortex ring momentum is comparable to the jet momentum. Given the constant vorticity independent of the jet momentum, a greater degree of interaction between the vortex ring and the fuel jet leads to more repetitive flame reattachment, resulting in more steady heat release.