Title: Gas turbine combustion instability generation mechanisms and practical control approaches 

Abstract: In engine combustion systems such as gas turbines and ramjets, pressure fluctuations are always present, even during normal operation. One of design prerequisites for the engine combustors is stable operation, since large-amplitude self-sustained pressure fluctuations (also known as combustion instability) have the potential to cause serious structural damage and catastrophic engine failure. The typical generation mechanisms of such undesirable combustion instability are discussed and highlighted. To dampen pressure fluctuations and to reduce noise, acoustic dampers are widely applied as a passive control means to stabilize combustion/engine systems. However, they cannot respond to the dynamic changes of operating conditions and tend to be effective over certain narrow range of frequencies. To maintain their optimum damping performance over a broad frequency range, extensive researches have been conducted during the past four decades. The present work is to summarize the status, challenges and progress of implementing such acoustic dampers on engine systems. The damping effect and mechanism of various acoustic dampers, such as Helmholtz resonators, perforated liners, baffles, half- and quarter-wave tube are introduced first. A summary of numerical, experimental and theoretical studies are then presented to review the progress made so far. Finally, as an alternative means, ‘tunable acoustic dampers’ are discussed. Potential, challenges and issues associated with the dampers practical implementation are highlighted.

Presenter bio introduction:

Prof. Dan Zhao is the fellow of the Academy of Royal Society of New Zealand (Academician). He is the Distinguished Fellow of the International Institute of Acoustics and Vibration. Prof. Zhao is the director of Master Engineering Studies at the University of Canterbury, New Zealand. He serves on 15 scientific journals as the chief and associate editors such as AIAA Journal, Progress in Aerospace Sciences, Journal of the Acoustical Society of America, Journal of the Royal Society of New Zealand, Aerospace Science and Technology, and Journal of Engineering for Gas Turbines and Power (ASME). Prof. Zhao has been awarded with another 10 fellowships from Engineering New Zealand, European Academy of Sciences and Arts, European Academy of Sciences as well as Royal Aeronautical Society, and Royal Society of Chemistry. His research expertise and interests include applying theoretical, numerical, and experimental approaches to study CO2 -free combustion science and technology, fabric drying, aeroacoustics, combustion instabilities; UAV aerodynamics; propulsion; energy harvesting; and renewable energy and fuel (ammonia and hydrogen). Prof. Zhao has already  accomplished and working on a number of research projects (~$18M) sponsored by various agencies and industries, like MBIE (NZ), Environment Canterbury Regional Council, Singapore Ministry of Education/Defense and Singapore Prime Minister Office (NRF).