An Experimental Investigation on the Trailing Edge Cooling of Turbine Blades by using PIV and PSP Techniques

Abstract

An experimental investigation was conducted to study the flow characteristics of the wall jets exiting from the trailing edge cooling slots at the pressure side breakout of turbine blades and the resultant film cooling effectiveness over the protected wall. In the present study, while air flow was supplied to simulate the hot main stream, the cooling jet streams were fed by using pure nitrogen. The mixing of the hot ambient gas into the cooling flows in gas turbines is replaced by the mixing of ambient air flow into the nitrogen jet streams over the protected wall. A high-resolution Particle Image Velocimetry (PIV) system was used to achieve detailed flow field measurements to quantify the evolutions of the unsteady vortex and turbulent flow structures in the cooling jet streams to examine the dynamic mixing process between the cooling jet streams and the main stream flows on the protested wall. Based on the theory of mass transfer analogy, the adiabatic film cooling effectiveness on the protected wall is expressed in the term of the oxygen concentration distribution over the protected wall, which is measured by using the pressure sensitive paint (PSP) technique. The detailed flow field measurements were correlated with the adiabatic cooling effectiveness maps to elucidate underlying physics in order to improve our understanding for a longer lifetime and better performance of turbine blades used for future advanced power.