In combustion devices such as aircraft gas turbine engines, large fluctuations in pressure, heat release rate, and heat transfer rate can occur due to interaction between acoustic waves and the combustion process. This is known as an acoustic combustion instability, and it can adversely affect combustor performance and can even cause system failure due to excess vibration or heat transfer. Currently industry does not have any reliable methods for predicting these instabilities; therefore, the combustor design process involves a significant amount of expensive testing. If an efficient and reliable tool for predicting these instabilities were available, the design process would be less time consuming and less costly.

The goal of my thesis project is to develop a method for using LES to simulate acoustic combustion instabilities and to use this method to predict the stability properties of an experimental combustor. Control strategies for reducing the fluctuation levels will also be developed and will be tested using the LES.

My current work is on the development of an efficient numerical method for the LES. Traditional numerical methods for predicting compressible flow are limited, for numerical stability reasons, to a time step that is inversely proportional to the acoustic speed. I am developing a method for compressible flow in which the time step is inversely proportional to the flow speed. This is expected to produce significant efficiency gains, since combustors typically operate at low Mach number, where the acoustic speed is significantly larger than the flow speed.