The present paper is directed to study aviation fuel combustion compared to that of natural gas in a gas turbine swirl Combustor. Finite-volume based CFD commercial package ANSYS Fluent 12 is used for the present investigation. The SST k-ω model is used to simulate turbulence. The non-premixed combustion model is used to simulate the reacting flow. Combustion of natural gas is sooty in nature. Thus, soot distribution in the combustor is investigated numerically using the two step soot model. Simple expressions for the soot formation and oxidation rates were employed. The radiation heat transfer equation was solved using the P-1 radiation model. The formation of thermal NO from molecular nitrogen was modeled and the prompt NO was also included in the computations. CFD modeling is validated against experimental temperature measurements for a swirl combustor when firing natural gas as referred to a previous paper. Using the SST-K-ω for predicting gas temperature distributions satisfy reasonable agreement with the experimental temperature measurements, except near the combustor upstream and in the vicinity of the combustor axis.