Experimental Study of Outlet Guide Vane Heat Transfer and Gas Turbine Internal Cooling

University dissertation from Lund University, Lund Institute of Technology

Abstract: Heat transfer in gas turbine related applications is investigated by steady state liquid crystal thermography (LCT) in this thesis. The work presented includes outlet guide vane heat transfer and gas turbine internal cooling.The heat transfer on the outlet guide vane (OGV) surface and its endwall region is investigated experimentally in a linear cascade test facility. The inlet flow angle is varied from +25º (on-design), to +40º and -25º (off-design). The Reynolds numbers tested are 300,000, and 450,000. On the OGV surface, boundary layer transition and separation affect the heat transfer significantly and they vary significantly with the inlet flow angle. On the endwall region, the effects of a horseshoe vortex (HV) on the heat transfer are clearly noticed at the leading edge area. For off-design conditions, the HV becomes more energetic than that of the on-design condition and the pressure side leg departs from the OGV at the inlet flow angle α = -25º.Experimental investigation of heat transfer and pressure drop in the turn region of a two-pass channel has been carried out. Results indicate that heat transfer on the smooth outer wall is dominated by the flow impingement. When ribs are fitted onto the outer wall, it is found that the heat transfer patterns are significantly altered. The presence of ribs augments the heat transfer at the penalty of increased pressure loss. Thermal performance is considered to provide optimized rib configurations. By proper application of guide vanes, the pressure loss over the turn region is substantially reduced while the heat transfer is only moderately changed. The combined effect of guide vanes and ribs on the heat transfer is also analyzed. The results can be used to optimize the internal cooling design for gas turbine blade tips.Jet impingement is an effective heat transfer method while the favorable performance is usually degraded by the cross-flow. Experimental measurements were conducted to study the effects of vortex generator pair (VGP) on the jet impingement heat transfer in cross-flow. The VGP is placed in the cross-flow channel and upstream of the jet exit. The jet Reynolds number is 15,000 and the cross-flow Reynolds numbers vary from 40,000 to 64,000. Results indicate that the VGP with common-flow-up (CFU) configuration promotes the jet penetration in cross-flow and augments the impingement heat transfer greatly on the target wall compared to the baseline case without the VGP. In addition, the parameters affecting the enhancement include the angle of attack of the VGP, the spacing between the VGP, the spacing between the VGP and the jet nozzle, the shape of the VGP, the height of the VGP, and also the cross-flow Reynolds number.

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