Application of Proper Orthogonal Decomposition to Light Intensity Measurements of Combustion Instability

Abstract

Proper Orthogonal Decomposition (POD) has been implemented in processing of highspeed movies of combustion light emission from two combustion instability experiments. Using the method of singular value decomposition, analysis produces a series of POD modes – orthogonal bases of linked spatial and temporal modes which are sorted based on decreasing singular value or “energy,” which indicates the variation and descriptivity contained within each POD mode. Without initially specified conditions or functional forms beyond raw data, the POD modes identify the measured frequencies of the chamber acoustic modes and show the physical behavior of the light emission associated with each POD mode. The major behaviors of the combustion light emission can be reconstructed using select POD modes, serving as an effective low-order approximation of high-order data. Based on this effectiveness, POD analysis shall be extended to the determination of flame describing functions from the temporal POD modes and measured pressure signals.