Computational fluid dynamics applied to internal gas-turbine blade cooling: A review

This paper reviews current capabilities for predicting flow in the cooling passages and cavities of jet engines. Partly because of the need to enhance heat transfer coefficients, these flow domains entail complicated passage shapes where the flow is turbulent, strongly three-dimensional (3-D) and where flow separation and impingement, complicated by strong effects of rotation, pose severe challenges for the modeler. This flow complexity means that more elaborate models of turbulent transport are needed than in other areas of turbine flow analysis, The paper attempts to show that progress is being made, particularly in respect to the flow in serpentine blade-cooling passages. The first essential in modeling such flows is to adopt a low Reynolds number model for the sublayer region. The usual industrial practice of using wall functions cannot give a better than qualitative account of effects of rotation and curvature. It is shown that Rayleigh number effects can modify heat transfer coefficients in the cooling passages by at least 50%, The use of second-moment closure in the modeling is shown to be bringing marked improvements in the quality of predictions. Areas where, at present, more computational fluid dynamics (CFD) applications are encouraged are impingement cooling and pin-fin studies.