The Effect of Vortex Core Distribution on Heat Transfer in Steam Cooling of Gas Turbine Blade Internal Ribbed Channels

Abstract

Steam has already been used as coolant of gas turbine blade internal cooling. A lot of investigations have been carried out to research the heat transfer performance of steam in ribbed rectangular channels. However, the micro-structure of the flow field especially the vortex distribution is not very clear. As the vortex caused by ribs is one of the main factors that enhance heat and mass transfer, it is very necessary to investigate the distribution of vortex in steam-cooled ribbed channels. The numerical simulation of steam flow field in 45° rib channels were carried out by using ANSYS CFX commercial program. The inlet Reynolds numbers are 30000 and 60000. The wall heat flux and inlet static pressure is 10kW/m2 and 0.3MPa, respectively. In order to find out the distribution and shape of all the main vortices, the technology of vortex core is applied, which is based on the critical point theory and Eigen-values of velocity gradient tensor. The distribution and shape of vortex core clearly indicates that the heat transfer strength of vortices positions is relatively higher than other places. There are four high strength vortices at the near-wall region between every two neighbored ribs. At the side wall which is located at the front side of ribs, high strength vortex exists and washes over the most part of the side wall. In the main flow region, the secondary flow caused by angled ribs can also be seen. The heat and mass transfer performance of steam in angled rib channels can be illustrated by the location and shape of vortex core.