Experimental And Numerical Study Of The Mechanism Of Internal Cooling In Gas Turbine Blade

In order to improve the thermal efficiency of gas turbine, turbine stage is and willbe operated at increasingly higher inlet temperature, which obviously exceeds theallowable temperature of blade material. The internal cooling has become anindispensable cooling technology for turbine blade now, and more complicated internalcooling geometries inevitably lead to a sophisticated heat transfer and fluid flowdistribution. Therefore, the study of the mechanism of internal cooling is quiteimportant to master the heat transfer and cooling technology of gas turbine blade.The mechanism of heat transfer and flow in the ribbed U-duct, which is a typicalconfiguration in the internal serpentine duct, is studied both experimentally andnumerically. The heat transfer is measured by the transient liquid crystal technology.The pressure drop and friction factor are also measured and used to form the empiricalcorrelation. In this dissertation, the heat transfer and flow in the turn region has beenoptimized by adding different configurations in this region. It is shown that, the turningvane restrains the flow separation near the tip of divider wall, and weakens the flowacceleration in the turn region, so it could greatly reduce the pressure loss. Adding theturning vane and ribs in the turn region could make the heat transfer in the U-duct moreuniform. The comparison between the experimental and numerical results shows that,the RANS method could provide acceptable engineering accuracy to analyze the flowfeature and heat transfer in the smooth U-duct and45deg ribbed U-duct. However theapplied turbulence model still can’t capture the flow separation and acceleration in theturn with good enough accuracy, and the heat transfer in the turn region is not verysatisfactory. The study of trapezoid U-duct shows that, the unsymmetrical duct wall willmake the secondary flow form two different vortices, in which the larger one is near thevertical wall. As a result, for the ribbed U-duct, the heat transfer on the vertical wall ishigher than inclined wall. The different mode how the coolant enters the U-duct haslittle effect on the heat transfer and flow in the duct.The internal cooling configuration of an F-class gas turbine blade has beenstudied in detail. The Experimental test,1D flow network calculation and3D RANSanalysis have been carried out to investigate the heat transfer and flow in this cooling system, and to analyze the cooling system design features. It is shown that the1D flownetwork method, in which the empirical correlation has been evaluated and corrected,and3D RANS method could provide acceptable prediction of the pressure and coolantdistribution in the complicated internal cooling system. At the stationary condition, thepressure and coolant distribution in the scaled blade is consistent with the primary one.On the rotating condition, the prediction of the pressure and coolant distribution in theblade by two simulation methods, are also consisted with each other. The experimentaltest by using transient liquid crystal and3D numerical method matches well, and theycould well reveal the heat transfer distribution in this true blade internal cooling system.The comparison has proved the reliability of the two methods on research the heattransfer and flow in complicated cooled blade.