Dynamic Response of a Premix Fuel Injector

Combustion oscillations (dynamics) have become a major challenge in the development of low-emission premix combustors. Numerous recent papers have considered the various mechanisms that drive oscillations, as well as acoustic features of the combustor and fuel system that participate in sustaining unwanted oscillations. The acoustic transfer matrix technique has been used in a number of recent analyses of both the combustion and fuel injection process. In this paper, the transfer matrix analysis is combined with a reduced order model of the fuel supply to calculate the magnitude and phase of the fuel system response to imposed pressure perturbations. The analysis is used to determine if a variable geometry resonator in the fuel system can be used to adjust the phase and gain of the fuel response to enhance stability. Experimental data recorded in a research premix fuel injector show that the reduced order model accurately describes the dynamic response of the fuel entering the premix passage. Using measured acoustic properties it is also shown that the variable geometry resonator studied here can produce a phase response for fuel delivery over a range of 70 degrees, with appreciable modulation of the main fuel flow. It is suggested that this variable phase response could be used to adjust the stability properties of a given combustor.Copyright © 2001 by ASME