Thermoacoustic Instabilities – Taming the “Ghost” of Gas Turbine and Rocket Engines

Abstract

Thermoacoustic instabilities (or “combustion instabilities”) come from the positive feedback between acoustics and unsteady combustion; unsteady combustion generates acoustic waves which propagate within the combustor, being reflected by the boundaries, and further disturb the flame to generate more acoustics. Due to the compactness and intensive heat release in gas turbine and rocket engine combustors, this coupling can generate catastrophically large pressure oscillations. Predicting it is very difficult since it requires resolving couplings across very different scales (acoustics, turbulence, and combustion). Full-scale experiments are extremely expensive, but lab-scale rig does not capture all key physics – a process of trial and error involving many very expensive full-scale tests (high pressure and temperature tests covering all operating cases) is usually needed to ensure that this instability is safely avoided. Thermoacoustic instabilities are thus called the “ghost” of aero- and rocket engines. This talk presents the state-of-the-art treatments in predicting and damping of this instability. More specifically, the state-of-the-art low-order network modelling methodology, and relevant vortex-sound-entropy coupling theories will be presented.

Speaker

Dr Dong Yang is an Associate Professor at Southern University of Science and Technology, Shenzhen, China. He is a recipient of the National Science Fund for Excellent Young Scholars (Overseas) in China. His research focuses on predicting and damping of thermoacoustic instabilities, with expertise in low-order network modelling and vortex-sound-entropy coupling theory. He got his first and Master’s degrees from Tsinghua University in Beijing, and his PhD from Imperial College London. His work won the Osborne Reynolds student Award 2017 -- top six PhDs in Fluid Mechanics in the UK, and has been highlighted by the Journal of Sound and Vibration as “2017 Highlight of Aeroacoustics research in Europe”. He has been invited by many leading companies such as Siemens, Reaction Engines, Shanghai Electric, Rolls-Royce, and AECC CAE to give talks or build collaborations on thermoacoustic instabilities. He is an organizer and co-chair of the 23rd International Congress on Acoustics, the Combustion Webinar, the 11th National Fluid Mechanics conference of China and the 51st Inter-Noise conference, and a reviewer for Journal of Sound and Vibration, Journal of Fluid Mechanics, Combustion and Flame, AIAA Journal, Journal of Engineering for Gas Turbines and Power etc.