Research On The Mechanism Of Flow And Heat Transfer Interaction In Anisotropic Turbulent Film Cooling Flows

Gas turbine is the core power equipment for efficient conversion and cleanapplication of energy. Film cooling as one of the key cooling methods with theincreasing of the initial temperature in modern gas turbine, is of great significance inensuring efficiency and safety of gas turbine. Film cooling is characterized as3-D nearwall complex convective heat transfer. Its turbulent flow and scalar transport controlledby near wall large scale coherent structures, is highly anisotropic. Meanwhile with thedevelopment of computer technology, three dimensional computational fluid dynamicstechnology based on viscous fluid dynamics has been more and more important in thefilm cooling investigations.This paper based on the detailed measurement of flow and heat transfer in filmcooling flows, builds up a database of film cooling flow and heat transfer under variousconditions. Therefore, the mechanism of flow and heat transfer interaction inanisotropic turbulent film cooling flows is revealed. An algebraic anisotropic turbulencemodeling method for the prediction of film cooling flows is developed to improve thenumerical accuracy of film cooling. Furthermore, with the aids of both experimental andcomputational research, the flow and heat transfer characteristics of film cooling on thesurface with curvature and pressure gradient such as showerhead and vane issummarized.The development of the algebraic anisotropic turbulence modeling methodstarts from the anisotropic correction of eddy viscosity, and further includes theanisotropic correction for turbulent scalar flux with the aid of the high orderform of generalized gradient diffusion hypothesis to improve the prediction ofnear wall Reynolds stress and turbulent scalar flux. This algebraic anisotropicturbulence modeling method is validated with a great amount of classic andin-housed experiments of film cooling.Detailed experimental investigation of film cooling vortex structures in theflow field and heat transfer result is conducted on the low speed film coolingtest rig. Different hole shapes are tested and both flow and heat transfer data areget. These data are used to validate the numerical model and further with the details of computational results, the mechanism of flow and heat transferinteraction in the complex turbulent film cooling flow is analyzed.For the investigation of showerhead film cooling, both experimental andnumerical studies are conducted. The algebraic anisotropic turbulence modelingmethod is proved to be validated for the prediction of film cooling under thecondition of curvature and pressure gradient. Therefore this method is used todiscuss the complex characteristics and mechanisms of film cooling on vaneapplication. The interaction mechanism of the film cooling jet with the mainflow field in showerhead and vane cases is summarized together with thecharacteristics of film cooling on different places of the vane.