Mode coupling due to the non-uniformly distributed heat release in combustion instabilities

In the present paper a low-order model is developed to investigate the combustion instabilities in a chamber with circumferentially non-uniform heat release. It is shown that the mode coupling can be brought by the non-uniformly distributed heat release. From the results it can be found that the instability frequency is less influenced by the mode coupling. The unstable growth rate, however, can be significantly affected by the non-uniformity of the heat release. In the longitudinal mode dominant instability case, the azimuthal acoustic mode becomes significant for the sine shaped heat distribution. However, the effects of vorticity waves can be neglected, as the magnitude is weak enough compared to the acoustic waves.