Development of combustion response functions in a subscale high-pressure transverse combustor

Abstract

Combustion response functions describe the magnitude and time lag behavior of a flame in response to unsteady pressure and velocity. By understanding the feedback between unsteady flowfields and heat release, the growth and decay of combustion instability can be better predicted. An automated data isolation and reduction method has been developed to generate meaningful graphical combustion response functions from a combination of pressure amplitude and various image analysis metrics. It was developed and tested using pressure measurements and high-speed imaging of combustion light taken from a single element at the midspan of an unstable high-pressure subscale transverse combustor. The code was used to isolate time slices of near stationary pressure amplitude and to process the corresponding images into combustion response approximated by aggregate intensity, intensity weighted spatial center, Proper Orthogonal Decomposition (POD), and Dynamic Mode Decomposition (DMD). Overall, the generated combustion response functions generally agreed with expected behavior of an element located at a first width (1W) velocity antinode and second width (2W) pressure antinode. Results from both POD and DMD successfully isolated the prominent spatial and temporal light emission behavior.