A review of models for the response of premixed flames to acoustic perturbations

What is it about?

Feedback between acoustic perturbations and heat release can result in thermoacoustic instabilities (see below). In this context, it is important to describe accurately how premixed flames respond to perturbations of the flow velocity of the premixture upstream of the flame. This response is in general not immediate, but occurs after some time. In other words, there is a delay between cause, i.e. the perturbation of velocity, and effect, i.e. the modulation of heat released by the flame. Indeed, the time delay is not single-valued, but distributed over time. For example, upstream portions of the flame might respond earlier, while the downstream "flame tip" responds later. The strength and temporal distribution of the delayed responses is crucial for the stability of the thermoacoustic feedback loop. The paper reviews more than two decades of work in this field. It presents the mathematical background and the advantages of the time-domain perspective for the analysis of flame dynamics. Furthermore, studies are reviewed that utilize the concept of distributed delays in order to devise approaches for suppression of instabilities.

Featured Image

Why is it important?

Thermoacoustic combustion instabilities are a severe challenge for the development of reliable, clean and flexible combustion technology. Most important applications are gas turbines for propulsion and power generation, but also rockets or process heaters.

Perspectives