Increasing Accuracy of the Gas Temperatures Pattern Calculation for GTE Combustor Using CFD

Abstract

It was found that the accuracy of the radial and circumferential non-uniformity modeling for the gas temperature pattern at the exit of the combustion chamber is unsatisfactory when using the k–ε turbulence model with the initial settings for the Ansys Fluent program. To reduce the non-uniformity of the temperature pattern at the exit of the combustion chamber, the degree of turbulent diffusion of gas components was increased with respect to the initial version of calculation, performed using the k–ε model of turbulence with the initial settings, by reducing the turbulent Schmidt number Sc. A numerical experiment was performed for the values of the Schmidt number Sc = 0.85 (default), Sc = 0.6, Sc = 0.4, and Sc = 0.2. The results of a numerical experiment confirmed the reductions of radial and circumferential non-uniformities with decreasing Sc, but theirs levels are different. Therefore, to ensure high accuracy in calculating both the circumferential and radial non-uniformities of the gas temperature pattern, it was proposed to use a variable value of Sc, depending on the gas temperature. The functional dependence of the turbulent Schmidt number Sc on the gas temperature was implemented in the Ansys Fluent program using the user function (UDF). The results of the gas temperature pattern modeling using the proposed UDF function for the turbulent Schmidt number Sc are in satisfactory agreement with the experimental data for both radial and circumferential non-uniformities of the gas temperature pattern at the exit of the combustion chamber.