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Abstract
The gas path over the turbine blades is a very complex flow field due to the variation of
ow regime and the corresponding heat transfer, This investigation is devoted to study the o and three-dimensional predictive modeling capability for airfoil external heat transfer /~ using pressure based solver PBS and density based solver DBS. The results show the C’effects of strong secondary vortexes , laminar-to-turbulent transition, and also show ~Jtagnation region characteristics.
Simulations were performed on an irregular quadratic grid with the Fluent 6.3 software package which solves the RANS equations by using finite volume methods with second order accuracy. Data were obtained for the exit Reynolds numbers equal the facility maximum point of2.50Xl06, including the blade aspect ratio of 1.17. It has been concluded in particular that rather fine computational three dimensional grids are needed to get accurate local heat transfer controlled by complex 3D structure of secondary flows.
Detailed heat transfer predictions are given for a power generation turbine rotor with 127 deg of nominal turning and an axial chord of 130 mm with highly three-dimensional blade passage flows that resulted from the high flow turning and flow boundary layer. Results of numerical simulation of the two and three-dimensional turbulent flow heat transfer in a transonic turbine cascade are presented. Employing several turbulence models (Spalart-Allmaras, RNG k-€ and SST k-ro model). The comparison was made with the experimental and the numerical results of Gieland colleagues [11] and a good agreement was found with the density based solver and Spalart Allmaras turbulence model.
The second part of the present study is devoted to predict the local and average Nusselt number over the three-dimensional turbine blade for different turbine loads with different Prandtl numbers 0.5, 0.7 ,land 1.25 and different aspect ratios 0.5 ,1 and 2 using Splart-Allamars model with DBS technique.