Grid Orthogonality Effects on Predicted Turbine Midspan Heat Transfer and Performance

Abstract

The effect of five different C type grid geometries on the predicted heat transfer and aerodynamic performance of a turbine stator is examined. Predictions were obtained using two flow analysis codes. One was a finite difference analysis, and the other was a finite volume analysis. Differences among the grids in terms of heat transfer and overall performance were small. The most significant difference among the five grids occurred in the prediction of pitchwise variation in total pressure. There was consistenc y between results obtained with each of the flow analysis codes when the same grid was used. A grid generating procedure in which the viscous grid is embedded within an inviscid type grid resulted in the best overall performance.

Leading Edge Film-Cooling Effects on Turbine Blade Heat Transfer

“…Thus, this model is likely to be invalid in a number of turbomachinery applications but for turbine blades, the boundary layers generally experience a favorable pressure gradient whereby this model is more likely to be valid. It has been used satisfactorily by Boyle and Giel (1992), Ameri and Amone (1994a, b), and Boyle and Ameri (1994) for heat transfer calculations on turbine blades without film cooling, and by Hall et al (1994), and Garg and Gaugler (1994) with film cooling. In fact, Ameri and Amone (1994b) compared the Baldwin-Lomax model and Coakley's q-co model against experimental data of Graziani et al (1980), and found that the algebraic model was able to produce many of the flow features better than the twoequation model.…”

“…2). Normal to the blade surface is the dense viscous grid, with y' < 1 for the first point off the blade surface, following Boyle and Giel (1992). Computations were run on the 8-processor Cray Y-MP supercomputer at the NASA Lewis Research Center, and on the 16-processor C-90 supercomputer at NASA Ames Research Center.…”

“…The term, gill holes, denotes the location of holes on a blade similar to that of gills on a fish. They recommend that a minimum y' value of 3.0 or less be maintained for the near airfoil mesh to achieve accurate heat transfer results, while Boyle and Giel (1992) recommended a value of y' about 1. They observed adjacent jet merging and a pronounced "stripping" pattern on the suction surface at low coolant flow rates, but at high coolant rates, the film-cooling flow followed a more spanwise trajectory resulting in a more uniform reduction in heat transfer at the vane surface.…”

Heat Transfer in Separated Flows on the Pressure Side of Turbine Blades

“…These are thought to be due to some truncation errors in the specification of geometry points, as other authors like Gehrer and Jericha [21] Boyle and Ameri [22] have reported. In order to solve such problem; a redesign of the geometry was performed while keeping the same pressure distribution and global geometry constraints.…”

Comparison between Hot and Cold Flow Conditions of Turbine Cascade

“…Using the Baldwin-Lomax turbulent model, Boyle and Ameri 9) observed a discrepancy between the numerical and experimental total pressure values at the 0.42 axial chord behind the blade. They attributed this discrepancy to the conjecture that the amount of diffusion in the wake predicated by the turbulent model is too small.…”