One of the driving requirements in gas turbine design is the combustion analysis. The reduction of exhaust pollutant emissions is in fact the main design constraint of modern gas turbine engines, requiring a detailed investigation of flame stabilization criteria and temperature distribution within combustion chamber. At the same time, the prediction of thermal loads on liner walls continues to represent a critical issue especially with diffusion flame combustors which are still widely used in aeroengines. To meet such requirement, design techniques have to take advantage also of the most recent CFD tools that have to supply advanced combustion models according to the specific application demand. Even if LES approach represents a very accurate approach for the analysis of reactive flows, RANS computation still represents a fundamental tool in industrial gas turbine development, thanks to its optimal tradeoff between accuracy and computational costs. This paper describes the development and the validation of both combustion and radiation models in a object-oriented RANS CFD code: several turbulent combustion models were considered, all based on a generalized presumed PDF flamelet approach, valid for premixed and non premixed flames. Concerning radiative heat transfer calculations, two directional models based on the P1-Approximation and the Finite Volume Method were treated. Accuracy and reliability of developed models have been proved by performing several computations on well known literature test-cases. Selected cases investigate several turbulent flame types and regimes allowing to prove code affordability in a wide range of possible gas turbine operating conditions.
Radiative heat transfer in a model gas turbine combustor
