Experimental Investigation on High Frequency Perturbation to Combustion Instability by Low Frequency Actuator in a Backward-facing Step Combustor

Abstract

Compared with the quasi-steady combustion process, the large pressure oscillation in the combustion unstable process contains rich physical characteristics and more severe structural damage phenomenon. The active control method is more flexible and efficient by controlling some parameters of the combustion system through the actuator, so as to destroy the coupling between heat release oscillation and acoustic disturbance. However, the existing active control method is limited by the lack of model and actuator frequency, which has limitations on the control ability of the unsteady process. In this paper, a low-frequency actuator is used to stimulate the fuel injection system of the rear step combustors, and the time series of the experimental pressure measurement of the combustors is analyzed qualitatively. It is found that the periodic excitation signal will trigger the modal conversion of the frequency and amplitude of the combustors, which makes the intermittent state of the system appear obviously in advance or lag phenomenon. Through the analysis of the pressure sequence recursion diagram, it is considered that the low frequency actuator excited by the high frequency periodic signal has an effect on the combustion state transition of the combustor.