A wrinkled flame interpretation of the open turbulent diffusion flame

Abstract

Measurements of fluctuating temperature in an open turbulent methane diffusion flame, using fine wire thermocouples, are reported. The radial evolution of the probability density function for temperature which emerges from these data suggest a mechanistic interpretation in terms of wrinkled or flapping flame behaviour. A model is proposed which exploits this description and which is shown to be capable of almost complete reconstruction of the measured pdf simply from the measured values of mean and variance. The same formalism enables the ambiguity in the relationship between temperature and a conserved scaler to be resolved and the statistics of the conserved scalar to be deduced from the temperature measurements. Such predictions are shown to compare favourably with availble data using a light scattering technique. The mechanistic component in the interpretation of data presented here encourages the view that the modelling of pdfs for scalars in open diffusion flames and fires, in particular, can be very significantly simplified by identifying a flamelet profile as the microscopic element in a turbulent ensemble.