Application of heat transfer at the combustor wall to attenuate self-excited thermoacoustic oscillations

Abstract

Self-sustained thermoacoustic oscillations (also known as combustion instability) arise in combustors when pressure and heat release fluctuations couple to produce high-energy sound waves. The need for diverse strategies to control these oscillations will increase as future design moves towards highly efficient, lean combustors. In this work, the impact of heat transfer at the combustor wall on the generation of thermoacoustic oscillations is examined through computational fluid dynamics. Characteristics of the thermoacoustic oscillations generated across cases with a range of thermal boundary conditions are compared to an adiabatic reference case. The amplitude of limit cycle oscillations in a Rijke tube is seen to decrease as wall temperatures increase. A stable combustor with a negative growth rate is observed when the full outer wall is heated to 900 K, and a sound pressure level reduction of 75 dB is achieved. The most efficient stable configuration is achieved when only the inlet duct wall is heated to 1000 K, requiring a minimum of 430 W of input power. The present work introduces an alternative stable combustor design and demonstrates that optimizing the temperature distribution of the combustor wall can effectively dampen thermoacoustic oscillations.