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

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.