Numerical Aero-Thermal Analysis of a Rib-Roughened Trailing Edge Cooling Channel at Different Rotation Numbers and Channel Orientations

Abstract

The present work considers the aero-thermal characterization of a rib-roughened cooling channel for the trailing edge of gas turbine blades, and is based on previous findings from a smooth channel configuration. The passage is characterized by a trapezoidal cross section with high aspect-ratio, radial inlet flow, and coolant discharge at both model tip and trailing side, where seven elongated pedestals are installed. In this study, heat transfer augmentation is achieved by placing inclined squared ribs on the channel central portion. RANS simulations with a SST turbulence model were performed using the commercial solver ANSYS CFX®v14. The numerical tool was first validated on the available experimental data and, subsequently, its capabilities were exploited in a wider range of working conditions, namely at higher rotation speed and different channel orientation. In this way it was possible to highlight the effects that ribs and working conditions have on the development of both flow and thermal fields. The results show that rotation and channel orientation produce contrasting effects. On the rib-roughened wall, rotation/orientation generates an increase/decrease of the heat transfer; conversely, on the trailing side region rotation/orientation has a negative/positive effect on the thermal field.

Effect of turbulence models' choice on the aero-thermal flow numerical validations within a ribbed trailing edge geometry

“…20,43,47 High orthogonal cells are obtained by the use of O-grids. 41 CFD calculations were performed thanks to the ANSYS Fluent 14.0 solver. In fact, Navier–Stokes equations are solved by means of a SIMPLE-like (Semi-Implicit Method for Pressure-Linked Equations) algorithm with a convective diffusive equation for the pressure correction to impose mass continuity considering density variation.…”

“…This is possible thanks to the recommended well-established method of the Fluid Engineering Division of ASME 44,45 allowing a fulfillment of the grid independence revision. This method, as applied to a wide range of CFD problems, is based on the generalized formulation of the Richardson extrapolation theory 42,49,61 proposed by Roache 41,42,47,61–63 to evaluate the called “Grid Convergence Index” (GCI) which represents the discretization error bands for the computed variable. 47…”

“…They concluded that the Open Foam code gives better results than those of CFX . Later on, the aerodynamic flow inside the same geometry of literature 18–20,42 was investigated by Pascotto 41 and Pascotto et al. 42 via SST RANS model for a prototype composed of 8 × 10 6 hexahedral nodes.…”

“…In recent times, Beniaiche et al. 43 performed an experimental analysis on the similar geometry of literature, 18–20,40–42 for three surfaces: smooth, + 60 °, and –60 ° ribbed ones. They were interested to the local HTC variations of the TE area.…”

Flow field inside a leading edge cooling channel with turbulence promoters in rotating conditions

“…In some applications, the k-o turbulence model showed superior performance in predicting the heat transfer, 14 whereas in other cases, the k-" turbulence model, even in conjunction with wall function, was identified as the most promising solution. 15,16 Actually the shear-stress transport (SST) k-! model is often assumed as the unique turbulence closure for simulating the effect of ribbed walls on heat transfer 17,18 and internal flow field, 19 with no assessment of performance of different turbulence models.…”