Experimental and PIV-method studies of lean mixture flames, focused on extinction during its propagation in a standard tube resulting from flame stretching

Abstract

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.The main goal of this work is to determine experimentally local stretch rate distribution along limit methane/air and propane/air flames – using Particle Image Velocimetry (PIV) method. It allows to obtain necessary moving flame velocity fields in a standard flammability column and, also, to recognize the flame structures. For this purpose each mixture was seeded with MgO particles (of known size) before entering the tube (column) – using a special system. The amount of seeds in the mixture, their dispersion system and the laser power producing a sheet of light penetrating the column – were carefully chosen (not to disrupt the combustion or flame propagation in it). After learning process, finally it allowed to obtain the good quality velocity field images in the region concern – acceptable for further processing. The methodology developed for these experiments proved to be reliable and able to supply analyses with repeatable data. On the basis of performed experiments it was possible to derive the flame stretch rate which causes its extinction for both mixtures.