HEAT TRANSFER ENHANCEMENT OF SWIRL COOLING BY DIFFERENT CROSSFLOW DIVERTERS

Swirl cooling is a promising cooling technology in gas turbine blade leading-edge. However, the swirl strength of coolant decreases rapidly along the swirl chamber, and there exists a low heat transfer zone between two adjacent nozzles. Moreover, the downstream heat transfer is always reduced by the crossflow. To solve this problem, the concept of swirl cooling with crossflow diverter was proposed, and the velocity fields and heat transfer performance were investigated in this paper. Numerical simulations were performed by using 3D steady flow solver of Reynolds-averaged Navier-Stokes equations (RANS). The turbulence model validations were performed against both smooth swirl chamber and circular tube with circumferential ribs, and the validation results pointed out that the SST k-. turbulence model had the highest accuracy in predicting the heat transfer in swirl chamber with diverters. To reveal the mechanism of crossflow suppression and heat transfer enhancement, the simulation results were compared with smooth swirl chamber under different Reynolds numbers. On this basis, the effects of crossflow diverter heights and locations were studied further. The results showed that for smooth swirl chamber, the swirl strength decayed linearly, and the heat transfer coefficients decreased rapidly, thus the high heat transfer zone cannot cover the whole region between these two adjacent nozzles. The circumferential velocity of the jet gradually decreased while the axial velocity increased, and the crossflow formed. Crossflow and downstream nozzle efflux produced interference effect. Because of friction effect, crossflow reduced the circumferential velocity of the downstream jets and made the jet deflect downstream. Thus, the high heat transfer area of the downstream target plane decreased sharply. For swirl chamber with crossflow diverters, the crossflow and downstream jets separated from each other. The ability of the downstream jet to penetrate the mainstream and scour the target surface was strengthened. Therefore, the heat transfer of the target surface near the downstream nozzle was enhanced. Higher Reynolds number contributed to a more obvious crossflow suppression and heat transfer enhancement effect.