Cooling of the turbine blade is a critical problem with respect to the increasing turbine inlet temperature. The general method for cooling the blade tip surface is to design a serpentine cooling channel with 180-deg turns inside the turbine blade. Turning vanes, ribs, dimples, protrusions and pin fins have been applied in the turning region in internal cooling channels to increase the cooling effect for the blade tip-wall. The double-layer, dome shaped turning vanes have been proved to be an internal cooling structure which can effectively enhance the heat transfer ability of the tip wall. However, the leading and trailing walls of the channel are equally important for cooling. And in the actual internal cooling channel, the cooling performance of each surface is the result of the combined action of all cooling structures in the channel. The rib is a typical cooling structure in the internal cooling passage of modern gas turbine.

In this paper, the effects ribs in a U-bend channel with double-layer, dome-shaped turning vanes on heat transfer enhancement are investigated. Numerical simulations are performed by solving 3D steady Reynolds-averaged Navier-Stokes (RANS) equations with *k*-*ω* turbulence model. The channel aspect ratio (AR) is 1:2 and hydraulic diameter is 93.13 mm, respectively. Based on the cooling air inlet velocity and the channel inlet hydraulic diameter, the inlet Reynolds numbers are ranging from 1x10^5^ to 6x10^5^. The detailed 3D fluid flow and heat transfer characteristics are presented and the overall performances of two-pass channel are also evaluated and compared with each other. The results revealed that compared with smooth channel, ribs can increase heat transfer area and destroy the development of boundary layer, thus enhancing the heat transfer performance. The heat transfer capacity of the tip wall is improved when the ribs are added. Under the same Reynolds number condition, the arrangement of the rib with large height and pitch is weaker in heat transfer and higher in pressure loss than that with small height and pitch cases. For the tip wall heat transfer, the effect of straight ribs is better than that of inclined rib, and for the leading/trailing wall, the heat transfer ability of straight rib is lower than that of inclined rib. In general, ribs will change the secondary flow patterns in the channel, and then change the heat transfer performance of the leading/trailing wall and the tip wall.


Effect of Ribs on Heat Transfer and Pressure Drop in a U-Bend Channel With Double-Layer, Dome-Shaped Turning Vanes

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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