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Blade and Vane Leading Edge Fillet on Endwall Cooling in Linear Turbine Cascades

DOI: 10.1615/IHTC15.gtb.009553
pages 3441-3454

Gazi Mahmood
University of Pretoria

Sumanta Acharya
Ring Companies Chair Mechanical Engineering Department University of Memphis, Memphis TN 38152

KEY WORDS: Heat transfer enhancement, Gas turbine, leading edge fillet, passage vortex


Endwall-temperature and flow measurements are obtained in two linear turbine cascades- one employs airfoils of blade profile and the other employs airfoils of vane profile. Same leading edge fillets on blade/vane profile are employed in the two cascades. The blade cascade operates at low speed atmospheric conditions while the vane cascade operates at high speed conditions with the exit Mach number near 1.0. The blade and vane profiles are obtained from the hub-side airfoils of the first stage turbine section of the GE-E3 engine. The scale ratio of cascade passage to the actual engine first stage is 10:1 for the blade cascade and 1:1 for the vane cascade. The geometry of fillet base is elliptical that extends from 0.30 axial chord upstream to pressure and suction side around the leading edge of the blade or vane profile. The profile of the fillet varies linearly from the blade/vane wall to the endwall and blends smoothly with the blade/vane wall away from the leading edge. Measured endwall-temperatures with constant heat flux in the blade passage provide Nusselt number distributions along the endwall with and without fillet. In the vane passage with and without fillet, the endwall temperatures are measured with the discrete film cooling flow from upstream of passage to obtain the adiabatic fill cooling effectiveness. The film cooling holes located between 0.20 and 0.27 axial chord upstream of the vane passage are cylindrical and oriented at 30° to the endwall. Flow measurements of static pressure and velocity vectors near the exit plane of blade cascade with and without the fillet provide the effects of fillet on the passage vortex primarily responsible for the endwall heating in the turbine passages. The distributions of the static pressure and velocity-vector magnitudes indicate smaller size and strength of the passage vortex in the blade passage when the fillets are present. The effects of weakened passage vortex are then clearly observed on the Nusselt number distributions that are smaller for the filleted blades than for the non-filleted blades. The film cooling effectiveness increases with the coolant flow blowing ratio in the vane passage with and without the fillet. However, the film cooling effectiveness are lower for the filleted vanes as the fillets mask some of the coolant holes blocking partially the coolant flow coverage.

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