Analysis of Turbulent Flow in 180° Turning Ducts With and Without Guide Vanes

Abstract

This paper presents a numerical study of the turbulent flows through a number of 2-D and 3-D 180° U-ducts, with and without guide vanes, using the Reynolds-averaged Navier-Stokes method. Computations have been first carried out for a 2-D U-duct flow (W/H = 1.0) with four turbulence models (V2F, k-ε, SST and Reynolds stress). The models’ capability for streamline curvature effects on turbulence and separation has been assessed, using flow and turbulence data. The effects of adding a guide vane inside the bend have been analyzed, to reduce/avoid flow separation. Three vanes with different radial locations have been studied, and the mechanism for pressure loss reduction has been examined. Analyses have been performed for turbulent flows in 3-D U-ducts with square cross-section and sharp 180° turning (W/D = 0.2), similar to the U-bends in typical turbine blade cooling passages. The predictions are compared with the data of outer wall pressure. The effects of the guide vane and outer-wall shape on the flow separation, secondary-flow vortices and pressure loss have been evaluated. The combined vane and uniform cross-section area provide a large benefit for the flow distribution and pressure loss reduction.

The effect of a hub turning vane on turbulent flow and heat transfer in a four-pass channel at high rotation numbers

“…Luo and Razinsky [17] presented a numerical study of the turbulent flow through an 180°sharp turn and a U-bend, respectively, with or without a turning vane. Their results of with the turning vane showed that the separation zone near the inner wall right after the turn is substantially reduced and the secondary flow kinetic energy (SKE) is also reduced by 38%.…”

“…It was concluded that heat transfer could increase as much as 65% while pressure drop could either decrease or increase depending on the specific configuration. The investigations [17][18][19][20] were all performed under non-rotation conditions.…”

Research on Aerodynamic Characteristics of Air-Cooled Turbine Blade with Conjugate Heat Transfer Method

“…In 2003, James D. Heidmann [4] developed coupling heat exchange solver and applied it in an air-cooled turbine stator blade with many kinds of materials. Jiang Luo and Eli H. Razinsky [5] used conjugate heat transfer analysis method to predict flow and the metal temperature of NASA turbine stator under the operation condition. Although the overall coincide was good, it should also be pointed out that there is room to improve for V2F model they used in the prediction of boundary layer transition and turbulent heat transfer especially in the suction surface.…”