Pressure Waves and Premixed Flames

Thursday, September 30, 1999 - 11:00am - 12:00pm
Keller 3-180
Andy Mcintosh (University of Leeds)
In this talk the interactions of pressure waves with premixed flames will be discussed. Initially acoustic wave interactions will be reported on, where the flame is treated as a flat low-speed diffusion driven combustion front characterized by simple one step chemistry. In the limit of high frequency, it is of note that it is predicted that there is a Khz resonant frequency, which as yet has still to be verified by experimenters.

Secondly investigations concerning the sharp reduction of pressure will be reported on, where it can be shown that there is a locus of extinction in Pmin - dP/dt space. This work is being extended to weakly strained flames.

Of interest are the faster, weakly compressible thick turbulent premixed flames. The faster speed of these flames is such that the entropy is no longer constant across such fronts. Using Rankine-Hugoniot theory, one can approximate the jump conditions in pressure and velocity whilst still leaving the structure un-determined. Recent investigations of the propagation of such flames in simple tube geometries have shown simple criteria for predicting the maximum growth rate of each mode. This depends on the sensitivity of the combustion front to pressure changes.