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.