Task 3.1 Interaction between thermoacoustic instability and flashback
The aim of this task is to study two flashback mechanisms in detail: flashback due to interaction between swirling flow and flame, and flashback due to thermoacoustic instabilities. The approach for both mechanisms will be based on the G-equation, which is a nonlinear partial differential equation for the flame surface (Moeck et al 2012). In order to capture flashback, the full nonlinear equation needs to be solved. A combined analytical and numerical approach will be used. The configuration to be considered is a backward-facing step (a tube with a sudden expansion in cross-section) with a premixed reacting flow, simulating either a Bunsen flame or a swirl flame; both are basic, but practically relevant, flames. A range of analytical tools will be employed to calculate the movement of the flame front, e.g. integral methods, perturbation techniques and multiple scale methods. The numerical work will be interlinked with the analytical work: it will help to test simplifying assumptions, and it will validate the analytical predictions.