Influence of spacing of a delta-winglet vortex generator pair on the flow behavior and heat transfer at the internal tip of gas turbine blades

Abstract

The hot erosion of turbine tip and the maintenance of tip reliability and service times have always been great challenges for researchers. This work presents a novel design of a tip wall with the internal surface fitted with delta-winglet vortex generator pairs (DVGP). Various spacing of DVGP is considered to study the influence of spacing on the internal tip heat transfer and flow behavior in the turn region of a serpentine cooling channel inside a blade. A smooth internal cooling channel is regarded as the Baseline. Five spacings of the leading edge of the DVGP, i.e., 0.03Dh(hydraulic diameter), 0.07Dh, 0.13Dh, 0.2Dh, 0.27Dh, respectively, are considered. Topological analysis in the skin friction field is introduced to better illustrate the 3D fluid flow. The inlet Reynolds number is set in the range of 10,000 to 50,000. Results show that the variation of the spacing between the DVGPs has a remarkable influence on the thermal performance of the internal blade tip. The heat transfer on each side of the DVGP is weakened increaseing spacing, which is caused by the movement of the attachment line on the surface of the DVGP and the weakening of the vortex energy. The optimal thermal performance appears for the narrow spacing (0.03Dh) of the leading edge of the DVGP, and the heat transfer augmentation is approximately 7.90% compared with the two-pass channel with a smooth tip. The delta-winglet vortex generator arranged narrowly on the internal tip is aimed for enhancement of heat transfer. The analysis and results of this work are beneficial to the tip design of internal passages in gas turbine blades.