Single-shot temperature and mixture fraction profiles by Rayleigh scattering in the development zone of a turbulent diffusion flame

Abstract

Single-shot laser Rayleigh scattering profiles have been obtained in the development zone of a turbulent diffusion flame of a diluted hydrogen jet issuing into a coflowing air stream. The Rayleigh scattering cross section that depends on the local molecular composition is calculated at each laser shot as a function of mixture fraction ( Z) and the temperature profile by the use of an algorithm involving a strained flame library. This processing provides the instantaneous profiles of T and Z, so that the radial structure of the reaction zones can be statistically investigated, apart from the flame motion, in terms of the pdf and correlations for the scalars and their gradients. The main result is the large regular spreading of peak temperature distributions down to low values that are far less than the extinction limit. This is attributed to the occurrence of local and intermittent extinctions due to the action of turbulent stretch.