Combustion Instability-Coupling Mechanisms Between Liquid Oxygen/Methane Spray Flames and Acoustics

The effects of acoustic perturbations on a liquid oxygen/methane spray flame have been experimentally investigated. The main objective was to learn more about the interaction between combustion-chamber processes and an externally enforced acoustic field. With an in-depth analysis of dynamic-pressure signals and optical diagnostics of the flame, several results have been obtained and are presented in this paper. It was possible to spatially resolve the location in the combustion chamber where the response of the flame to the acoustic wave was highest. By reconstructing the acoustic pressure and velocity fields, and comparing these with excited hydroxyl radical, chemiluminescence (OH*) images of the flame, it could be shown that the flame predominantly reacts on the velocity fluctuations and not on the pressure fluctuations. All results were consistent and allowed for the conclusion that the coupling mechanism between combustion and acoustics in this experimental setup is predominantly velocity driven.