CFD VALIDATION AND VERIFICATION METHODS FOR MODELING THE TEMPERATURE FIELD AT THE OUTLET OF THE COMBUSTION CHAMBER BASED ON THE RESULTS OF EXPERIMENTAL STUDIES AND MESH CONVERGENCE ANALYSIS

Abstract

This research addresses the important problem of verifying and validating a CFD methodology for predicting the temperature distribution at the combustor exit in a small gas turbine engine (SGTE). The object of the study is the processes governing the formation of the temperature distribution at the combustor exit of a small gas turbine engine. The relevance of the study is that the exit temperature distribution directly affects the thermal conditions of the turbine nozzle guide vanes and rotor blades, their service life, and the efficiency of utilizing the energy of the combustion products. The objective of this work is to verify, through a grid convergence analysis, and experimentally validate a CFD methodology for modeling flow and combustion processes in a combustor in order to improve the accuracy of predicting the combustor exit temperature distribution during the design stage. To achieve this objective, the following research tasks were completed: a three-dimensional CFD methodology originally developed for full-scale gas turbine engines was adapted for small gas turbine engines; a grid convergence study was performed using the Grid Convergence Index (GCI) methodology; a comparative assessment of the k−ω SST, k−ε Realizable, and modified k−ω SST turbulence models was carried out; and the numerical results were validated by comparison with experimental data on the temperature distribution and total pressure loss. Numerical simulations were performed in ANSYS Fluent 2025 R1 using the finite volume method. Turbulence was modeled using the k−ω SST and k−ε Realizable models, combustion was simulated with the Non-Premixed Combustion model, fuel droplet motion was described using the Discrete Phase Model (DPM), and radiative heat transfer was accounted for using the Discrete Ordinates (DO) model. The grid convergence analysis demonstrated a numerical order of convergence of p = 3.2553, while the GCI value for the finest mesh was 0.1874%, confirming that the numerical solution is essentially independent of further mesh refinement. The comparative analysis of turbulence models showed that the modified k−ω SST model provides the most accurate prediction of the radial temperature non-uniformity. The scientific novelty of this work lies in the adaptation and verification of a CFD methodology for combustor simulations under the operating conditions of small gas turbine engines, while accounting for the scaling effects specific to SGTEs, and in identifying the turbulence model that provides the most reliable prediction of the combustor exit temperature distribution. The practical significance of the results lies in the development of a CFD methodology that accurately predicts the combustor exit temperature distribution and total pressure loss during the design stage, thereby reducing the need for costly experimental testing, shortening the combustor development cycle, and improving turbine durability and reliability