Coupled CFD and Heat Transfer Analysis for a Small Scale Gas Turbine Combustor

Abstract

Gas turbine combustor design process has significant number of design parameters because of contained complex phenomena. One of the most complicated of these is the heat transfer process of combustor liners. Heat transfer studies are performed in preliminary design phase by the help of one-dimensional tools and combustor geometry is shaped to satisfy design requirements. However; in the detail design phase, a fine tuning can be required to optimize it by using 3D CFD analysis. Conjugate heat transfer is a powerful tool to simulate interaction between reacting flow and combustor liners in detail design phase. But it is difficult to use computationally expensive conjugate heat transfer analysis in design iterations for calculating liner metal temperatures because of the high computation times. Its application will be mainly limited to optimized final geometries and steady simulations. On the other hand, when the 3D liner temperatures are required for structural evaluation during the preliminary design phase; coupled analysis of Finite Element Analysis (FEA)/ Computational Fluid Dynamics (CFD) can provide quick alternative solution. Coupled analysis requires lower mesh size and less calculation time comparing to the conjugate analysis. During a coupled analysis, an iterative boundary information exchange is conducted until the desired convergence criterion is reached. In this study, a series of numerical analyses are evaluated and the relevant rig test thermal paint results are presented. Numerical analyses consist of coupled analyses with various boundary condition cases. Some of these cases have the complete set of boundary conditions and they assumed as comparable to the test condition. In the coupling process, FEM use the near wall gas temperature data that comes from CFD solution and CFD uses wall temperature data that comes from the FEM solution. Heat transfer coefficients are not coupled and they are obtained from empirical heat transfer correlations. An atmospheric combustor test rig was used to apply thermal paint and thermocouple measurements were taken from the combustor outer liner. Numerical and experimental values of the liner temperatures are also compared and analyzed.