Effects of fuel variation and inlet air temperature on combustion stability in a gas turbine model combustor

Abstract

In this study, influences of fuel variation and inlet air temperature on the combustion stability characteristics in a gas turbine model combustor were experimentally investigated. Test fuels involved three selected single component hydrocarbons, including one linear alkane (n-decane), one branched alkane (iso-octane) and one cyclic alkane (methylcyclohexane (MCH)). RP-3 jet fuel was also selected as a technical reference. For all the fuels, experiments were conducted at a fixed equivalence ratio of 0.86 and varying inlet air temperatures from 383 to 483 K. Results showed that RP-3 and n-decane exhibited similar stability behaviors. At low inlet air temperatures, when the combustor was fueled with RP-3 and n-decane, the flame was stabilized and anchored in the combustor. The combustor then shifted to thermo-acoustically unstable state when the inlet air temperature exceeded a threshold value, which was associated by large-scale flame shape variations. On the other hand, noticeable differences can be observed for MCH and iso-octane flames, which featured thermo-acoustically unstable combustion throughout all the tested conditions, and unique mode-shift phenomenon was observed when the inlet air temperature was raised from 403 K to 423 K. Additional flame dynamics was visualized by OH⁎ chemiluminescence imaging. The underlying mechanisms that led to the differences in combustion stability and flame dynamics of the tested fuels were discussed with respect to their differences in physicochemical properties.