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 §ame in response to unsteady pressure and velocity. By understanding the feedback between unsteady §ow¦elds 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 ¦rst 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.

Experimental Investigation of Injection-Coupled High-Frequency Combustion Instabilities

“…DMD was applied to the high-speed flame radiation data in order to investigate the flame dynamics at the frequencies of interest. The DMD method has been used in past thermoacoustic instability research in order to extract the response of rocket combustor flames from visualisation data [3,14,16,29].…”

“…However, important research questions could not be answered by line-of-sight integrated 1D flame radiation measurements. In other experiments with less challenging environments than BKD, optical access has successfully been applied [13,14,21,23,29]. In these experiments, high-speed flame visualisation allowed further insight into the flame response to acoustic oscillations.…”

Modeling of a coaxial liquid oxygen/gaseous hydrogen injection element under high-frequency acoustic disturbances

“…Dynamic mode decomposition is described by Schmid [6] and is useful for identifying and sorting coherent §uctuations of data at di¨erent frequencies. Dynamic mode decomposition is often applied to study periodically §uctuating phenomena and has been previously used in combustion instability research in order to detect coherent §uctuations of §ame visualization data [7,8].…”