Recent works have confirmed that the propagation of leading-edge flames is the stabilization mechanism of turbulent lifted flames. Strong interactions between dynamics, mixing, and chemical reactions control the sustaining flame. Simultaneous and conditional measurements are needed to investigate the stabilization of turbulent lifted jet flames. The present paper focuses on the influence of flow dynamics on turbulent flame stabilization by means of simultaneous particle-image velocimetry (PIV) and OH planar laser-induced fluorescence (PLIF) measurements.
First, the turbulent field in the cold flow upstream of the flame base was determined. Turbulent properties of the flow at the flame base are important data for numerical simulation and modeling. It is essential to discriminate the cold flow from the hot gases since the velocity is higher in hot gases due to thermal expansion. Thus, to avoid overestimating the velocity fluctuations in the flame stabilization region, the fields of average and fluctuating velocity were measured within an analysis window. This window was attached to the instantaneous flame base, which followed it in its oscillating motion. With such an analysis window, only turbulent properties in the cold flow were sampled. Such data of the turbulent field at the flame base are useful to provide initial conditions to direct numerical simulation (DNS), comparison information to large eddy simulation (LES), and relevant validation of the Reynolds average Navier-Stokes (RANS) model, where intermittency is not accounted for.
Second, the unsteady influence of the turbulent flow on the leading-edge flame was investigated. The leading-edge flame was identified on each OH PLIF image, and local dynamic properties of the flow were measured from PIV meshes placed along the normal of OH outline at the leading-edge location.