COMPUTATIONAL FLUID-DYNAMICS APPLIED TO INTERNAL GAS-TURBINE BLADE COOLING - A REVIEW

This paper reviews current capabilities for predicting flow in the coo ling passages and cavities of jet engines. Partly because of the need to enhance heat transfer coefficients, these flow domains entail compl icated passage shapes where the flow is turbulent, strongly three-dime nsional (3-D) and where flow separation and impingement, complicated b y strong effects of rotation, pose severe challenges for the modeler. This flow complexity means that more elaborate models of turbulent tra nsport are needed than in other areas of turbine flow analysis, The pa per attempts to show that progress is being made, particularly in resp ect to the flow in serpentine blade-cooling passages. The first essent ial in modeling such flows is to adopt a low Reynolds number model for the sublayer region. The usual industrial practice of using wall func tions cannot give a better than qualitative account of effects of rota tion and curvature. It is shown that Rayleigh number effects can modif y heat transfer coefficients in the cooling passages by at least 50%, The use of second-moment closure in the modeling is shown to be bringi ng marked improvements in the quality of predictions. Areas where, at present, more computational fluid dynamics (CFD) applications are enco uraged are impingement cooling and pin-fin studies.