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Heat Transfer Analysis of Cooling Channels with the Blade-shaped Feature
Abstract
This dissertation features rotating, blade-shaped, two-pass cooling channels with varying aspect ratio (AR) under various operating and surface conditions. The cooling channels in turbine blades have variation in cross-section and orientation with respect to rotation to maximize the cooling space within the airfoils. The effect of the blade-shaped feature on the heat transfer and pressure loss was investigated by comparing the results to a planar design with a similar geometry. The coolant travels radially outward in the first passage (AR = 4:1) and radially inward in the second passage (AR = 2:1). The cooling channels were oriented such that the first and second passes were angled at 50 deg and 105 deg from the direction of rotation, respectively. The copper plate method was used to calculate the local, regionally-averaged heat transfer coefficients. The boundary conditions were: inlet Reynolds number from 10,000 to 45,000 and rotational speed from 0 to 400 rpm. In addition to the smooth surface case (baseline case), the cases with the 45-deg angled ribs in various orientations and a tip turning vane were also investigated.
The numerical results from computational fluid dynamics (CFD) simulations proved that the 180-deg, blade-shaped turn induces a swirling motion in the second passage, which enhances turbulence and heat transfer. The experimental results concluded that the rotational effect is reduced in the blade-shaped design when compared with the planar design due to the feature of angled rotation. Among the studied ribbed cases, the 45-deg usual ribs showed both the highest heat transfer enhancement and pressure loss while the criss-cross case had the lowest. The effect of a tip turning vane decreased the overall heat transfer and pressure loss in the cooling channels due to reduced turbulence in the second passage. However, the tip wall heat transfer was increased by the turning vane with enhanced flow velocity and turbulence. Taking heat transfer and pressure iii
loss into account, the case with both the 45-deg criss-cross ribs and the turning vane presented the highest thermal performance among the studied cases and operating conditions. The experimental data in this dissertation provides invaluable information for gas turbine designers.
Keywords: Gas Turbine Cooling; Rotating Heat Transfer; Blade-shaped Cooling Channel
Citation
Chen, I-Lun (2022). Heat Transfer Analysis of Cooling Channels with the Blade-shaped Feature. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198755.