Growth Rate and Flame Structure of Turbulent Premixed Flame Kernels in Supersonic Flows

A fundamental study of the radial growth and flame surface characteristics of freely propagating spherical flames is conducted in a 50 × 50 mm, M = 1.5 supersonic wind tunnel. Free stream turbulence is enhanced via passive and active turbulence generators upstream of the converging-diverging nozzle. Methane-air flame kernels are ignited via a single pulse of a frequency doubled green (532 nm) Nd:YAG laser. Simultaneous stereoPIV/OH PLIF measurements and asynchronous Schlieren and OH chemiluminescence are collected at several downstream locations to evaluate the flame kernel evolution. Time averaged parameters: turbulent displacement velocity, mean and rms velocities, turbulence autocorrelation and energy spectra are presented. Extra consideration is given to the terms pertinent to numerical model evaluation in supersonic flows.