Abstract
We have performed nonintrusive thermometry in rich ethylene/air flames using a frequency measurement based on laser-induced gratings. Light from a cw probe beam is coherently scattered from a thermal or electrostrictive grating induced by the pulsed pump beams. The Doppler modulation of the signal beam is determined by the local speed of sound, from which a temperature can be extracted. Soot particles, acting as blackbody absorbers, do contribute to the signal. (Author)