Numerical Simulation of Combustion Processes in a Gas Turbine

The type of the fuel, upstream and downstream flow conditions, fuel injection and mixing processes together with the geometry of the combustion chamber have a significant effect on efficiency, power, fuel consumption, noise and emission of the gas turbines. These contributions can be considered also in the virtual prototyping of combustion chambers, by which significant amount of time, cost and capacity can be saved. However, the accuracy of these approaches must be within 5-10 % for industrial relevancies. Hence, a three dimensional, turbulent flow and gas phase combustion has been modelled in a tubular combustion chamber of a gas turbine with the main goal of comparing the effect of different combustion models and solid wall boundary conditions with real tests. Four combustion models as Eddy Dissipation Model (EDM), Probability Density Function Flamelet Model (PFM), Burning Velocity Model (BVM) and Fluent Non-Premixed Model (FnPM) have been applied beside using k-epsilon turbulence model in the simulations. Three different incoming mass flows were implemented according to the measurements, which originate from Serag-Eldin and Spalding's paper [1.]. Although natural gas has been used in the real tests, methane combustion has been modelled in the simulations, because the dominant component of the burnt natural gas was methane in 93.63 %. The results were examined in 3 cross sections at certain axial distances along radii. The closest results to the measurements were provided by FnPM, most probably due to the more accurate thermal boundary conditions at the solid walls. In that case, the temperature differences between the measurements and the simulations were within the 30 % error margin in the 100 % of the investigated radius on the average, within 10 % in the 98.6 % and within the 5 % in the 79.1 %.