THE AUGMENTATION OF INTERNAL TIP HEAT TRANSFER IN GAS TURBINE BLADES USING A PAIR OF DELTA-WINGLET VORTEX GENERATORS

The present study provides a novel method to enhance the heat transfer on the internal tip surface of gas turbine blades. Effects of delta-winglet vortex generators (DWVGs) and their angle of attack on the vortical structures and mechanism of enhanced heat transfer are considered. Seven different angles of attack are included: 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees. The Reynolds number varies from 10,000 to 50,000. Flow topology analysis is applied to better understand the evolution of vortices in the turn region. Results show that a vortex is induced on the leeward side of the DWVGs as the angle of attack is greater than 0 degrees, which substantially enhances the local heat transfer. In addition, an extra saddle point is also generated at the tip surface on the windward side of the DWVGs as the angle of attack is greater than 45 degrees, which indicates that a vortex is formed. The internal tip heat transfer increases as the angle of attack of the DWVGs is increased. The optimal design is reached if the angle of attack is greater than 60 degrees. Compared with the smooth channel, the heat transfer and overall thermal performance are enhanced by up to 9.5% and 8.1%, respectively. This study elaborates the flow physics and heat transfer processes using topological analysis, which is helpful in the design of cooling processes of turbine blades.