Preethi Rajendram Soundararajan - Towards decarbonising combustion: on the challenge of thermoacoustic instabilities

Aviation is widely recognised as one of the most challenging sectors to decarbonise, with the high-altitude release of emissions further complicating efforts to reduce its climate impact. Two key pathways being pursued by the aviation industry are the use of sustainable aviation fuels (SAFs), which comprise blends of plant-derived hydrocarbons, as an intermediate solution, and hydrogen as a long-term carbon-free fuel. While these alternative fuels offer environmental benefits, they also introduce new scientific challenges, particularly in the form of thermoacoustic instabilities.

Thermoacoustic instabilities arise from complex interactions between fluid flow, combustion, and acoustics. Their consequences include intense noise and vibration, and, in severe cases, catastrophic engine failure. Consequently, they represent a major obstacle to the development of next-generation low-carbon systems.

This talk will explore the fundamental mechanisms underlying thermoacoustic instabilities. The first part will examine how minor variations in liquid hydrocarbon fuels influence instability characteristics. The second part will focus on hydrogen combustion and demonstrate how hydrogen can give rise to new forms of coupled flame oscillations that are not observed in conventional systems. The talk will also discuss how low-order theoretical models can be used to predict instabilities at an early design stage. Finally, future perspectives on the use of active control strategies for suppressing thermoacoustic instabilities will be presented.