Application of the time lag local model to a flame of premixed

A way to reduce pollutant emissions is the lean premixed combustion. Unfortunately this combustion induces strong instabilities. In turbine chambers, the knowledge of these combustion instabilities is therefore important. Our study on instabilities is performed in a gas turbine combustion chamber, close to industrial design. The Fourier transform of the CH and pressure signal allows to classify the instabilities in three categories: low frequency instabilities, acoustic instabilities and convective instabilities. The local study of the CH chemiluminescence shows that the instabilities are located in the different zones of the flame according to combustion condition and fluctuation frequency. The time lag model allows to predict the favorable conditions for amplification of convective instabilities. We propose to apply locally this model in order to predict the favorable zones for convective instability according to operating regime. (author)