Flow visualization of longitudinal vortices induced by an inclined impinging jet in a crossflow—effective cooling of high temperature gas turbine blades

Abstract

One of the most fundamental principles to improve the energy conversion efficiency is to raise the working temperature of a gas turbine. In order to realize high temperature gas turbines, development of effective cooling system of turbine blades is indispensable. The attention was paid to the utilization of longitudinal vortices to enhance the heat transfer from the inner surfaces of turbine blades. Effectiveness of longitudinal vortices in enhancing wall heat transfer were already confirmed for the case of a disturbed flat plate boundary layer with the insertion of a wing-type vortex generator (WVG) attached to a large-eddy-break-up (LEBU) plate. Pressure loss due to a form drag of the WVG, however, was not small. Then, longitudinal vortices generated by an inclined jet (VG jet) into crossflow have been examined to apply for effective cooling of gas turbine blades. Flow visualization and heat transfer experiments were conducted for a duct flow including longitudinal vortices without the insertion of any body in addition to a conventional impinging jet with crossflow. It was experimentally demonstrated that jet impingement is effective for heat transfer augmentation even in the case with crossflow, and that the longitudinal vortices have been confirmed to be generated by the insertion of the VG jet. The generated vortices are expected to effectively enhance the heat transfer from the inner surface of the blades of a gas turbine.