Analytical modeling of thermoacoustic instability influences in gas turbine combustors: A detailed parameter sensitivity analysis

Abstract

In this study, the effects of various system parameters on combustion instability were numerically identified through a network-based thermoacoustic model using the concept of a transfer function. The acoustic transfer function was derived from the wave equation and various conservation laws in a two-duct system consisting of a nozzle and combustion chamber that is a simplified form of a gas turbine combustor. From the current numerical approach, the major parameters affecting the system acoustics, such as the duct length, area ratio, sound speed ratio, and Mach number, as well as the inlet and outlet acoustic boundary conditions, were defined explicitly, and a method for intuitively examining their influence was presented. The gain (nf) of the flame transfer function was noted to have a complex effect in combination with factors such as temperature ratio and area ratio, and the time delay (τf) was one main dominant factor that determined the main characteristics of instability, resulting in mode transition as well as changes in frequency and growth rate of the instability.

Keywords

• Gas turbine combustion
• Combustion instability
• Thermoacoustics
• Analytical approach
• Network model