Control of thermoacoustic instability in a turbulent combustor using delayed acoustic self-feedback

What is it about?

Thermoacoustic instabilities are large amplitude, self-sustained periodic oscillations observed in practical gas turbines and rocket engines used for propulsion and power generation applications. Such instability results from positive feedback between the heat release rate and acoustic pressure fluctuations. The presence of these large amplitude acoustic pressure oscillations can severely affect the structural integrity of a combustor. This paper is about reducing such instabilities in a turbulent combustor using delayed acoustic self-feedback. Essentially, we couple the acoustic field of the combustor to itself and try to understand the dynamics of such a system, and how much we can reduce the amplitude of acoustic pressure fluctuations during the state of thermoacoustic instability.

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Photo by Jacek Dylag on Unsplash

Photo by Jacek Dylag on Unsplash

Why is it important?

Delayed acoustic self-feedback achieved through a single connecting tube provides a promising control mechanism to suppress thermoacoustic instability in turbulent combustors. Unlike in traditional active closed-loop controls used in thermoacoustic studies, we do not need to preprocess the acoustic pressure signal acquired from the combustor prior to feedback using any electromechanical devices in the method of delayed acoustic self-feedback. We are able to suppress thermoacoustic instability by more than 90%.

Perspectives