An effect of fuel flow modulation on the combustion instability in a model gas turbine combustor

Abstract

Combustion instability is a serious obstacle for the lean premixed combustion of gas turbines and can even cause fatal damage to the combustor and the entire system. Thus improved understanding of mechanisms of combustion instability is necessary for the design and operation of gas turbine combustors. In this study, we investigated the cause of the combustion instability in a rearward-step dump combustor with respect to the fuel flow modulation; choked fuel flow and unchoked fuel flow. We observed various types of combustion instabilities with respect to the change of equivalence ratio and fuel flow conditions. The combustion instability mainly results from thermo-acoustic instability and the instability case was affected by the modulation of fuel flow. Particularly in the unchoked fuel flow condition, we found that the oscillation time of combustion instability is highly related to the convection time of the fuel, which is defined as a flowing time taken from fuel inlet to the dump plane.