Premixed flame propagation in turbulent flow by means of stereoscopic PIV and dual-plane OH-PLIF at sustained kHz repetition rates

Abstract

This paper describes an experimental study on the propagation of premixed flames through a flow with well-defined turbulence characteristics. In this study, multi-plane OH planar laserinduced fluorescence (OH-PLIF) and stereoscopic particle image velocimetry (SPIV) were applied simultaneously at 10 kHz to measure the local three-dimensional displacement velocity of unstabilized, freely propagating flames passing through a premixed flow of methane and air. The dual-plane OH-PLIF data was used to track both reaction zone location and flame-normal orientation, while SPIV was used to track the three-component velocity field. The vectorial difference of the two produces a direct, time-resolved measurement of the local 3D displacement velocity of the flame. The use of unstabilized, freely propagating flames eliminates spatiotemporal dependence of local 3D displacement velocity associated with burner-or aerodynamically-stabilized test flames. Statistics of local 3D displacement velocities are presented. These show values ranging from slightly negative up to approximately eight times the laminar flame speed. Instantaneous flame-normal orientation with respect to the direction of local fluid velocity is identified as one parameter affecting instantaneous displacement velocities.

A direct numerical simulation study of flame structure and stabilization of an experimental high Ka CH4/air premixed jet flame

“…Negative displacement velocities are observed in highly curved regions with the centre of curvature in the products [20] and at large tangential strain rates [24] when the diffusion flux exceeds the adverse convection flux. Despite the significance of the negative displacement speed in turbulent premixed combustion, it is infrequently reported in experimental measurements due the difficulty of tracking the flame surface, flame normal vector, and flow field under turbulent reacting conditions and in three dimensions [26]. Coriton et al [27,28] studied turbulent premixed flames in a counter-flowing configuration of fresh reactants issuing against burnt products.…”

Measurement of local flame speeds in the thickened flamelet regime using simultaneous 10 kHz TPIV and OH/CH2O PLIF

“…[14][15][16] However, this technique requires many views for turbulent flows, with eight being employed by Weinkauff et al 14 and ten in Floyd et al 15 Another technique to map the 3D flame is though the use of multiple-plane measurements. For example, Trunk et al 3 used dual-plane OH PLIF measurements, with the assumption of a linear flame between the two planes. However, this technique requires an additional imaging system and is limited by the linearity assumption.…”

“…To account for 3D effects, Steinberg et al 2 and Trunk et al 3 used multiple planes of high speed (10 kHz) OH PLIF with a single plane of PIV to track edge flame dynamics and flame propagation, respectively. The location to which flame segments would passively convect was compared to the actual position is subsequent frames, with the difference being related to the propagation speed of the flame and the time between measurements.…”

Investigation of extinction and re-ignition in piloted turbulent non-premixed methane–air flames using LES and high-speed OH-LIF

“…Steinberg et al [22] for instance applied stereoscopic Particle Image Velocimetry (PIV) along with dual cross-plane OH-LIF to investigate flame holes in highly sheared non-premixed flames. More recently Trunk et al [23] applied stereoscopic PIV along with dual-plane OH-LIF to estimate the flame speed in a freely propagating premixed flame. Unsteady simulations such as Direct Numerical Simulation (DNS) or LES on the other hand can provide timeresolved, three-dimensional data of the velocity and scalar field and potentially predict transient processes in turbulent flames.…”