Combustion instabilities in lean premixed systems

Combustion instabilities are one of the most costly and technically challenging issues in lean, premixed combustion systems. While combustion instabilities, or thermacoustic oscillations more generally, have been noted in a variety of applications for several centuries, they are particularly problematic in lean, premixed combustion systems. Combustion instability is characterized by undesirably high acoustic and heat release rate oscillations inside a combustor chamber. In this chapter, we discuss the fundamentals of thermoacoustic feedback cycles, as well as the different coupling mechanisms by which combustor system acoustics create a feedback loop with flame heat release rate oscillations. Finally, an overview of combustion control strategies, particularly those employed in lean combustion systems, is discussed with references to future design and research directions.