63922 - Combustion Dynamics Tutorial 

Combustion dynamics is a costly and complex issue that affects both power generation gas turbines and aircraft engines, particularly in dry low emissions technologies. Driven by the coupling between combustor acoustics and heat release rate oscillations from the flame, this instability manifests as high-amplitude fluctuations in combustor pressure, flow, and flame heat release rate. These thermoacoustic instabilities can cause issues with flame stability, turndown margin, emissions, and engine operability; if left unchecked, instabilities can cause significant damage to the engine, resulting in shortened operational times and longer maintenance intervals. This tutorial provides a foundational overview of this important challenge in gas turbine design. We will cover the controlling physical processes that drive these instabilities, including combustor acoustics, thermoacoustic coupling, flow field oscillations, and fuel effects. Examples from both the scientific literature as well as engine operation are used to explain each of these critical physical properties that drive the combustion instability phenomenon. Mitigation strategies, including passive control, active control, and combustor monitoring strategies, will also be discussed. Case studies, both historical and current, will be presented in each section to illustrate the importance of this phenomenon in gas turbines and the interaction between a combustor design and its stability margin.