Experimental Investigations on Cooling Air Ejection at a Straight Turbine Cascade Using PIV and QLS

Abstract

Due to the high turbine inlet temperatures in modern aircraft engines the adoption of several cooling techniques in the first turbine blade rows is state of the art. For this reason the influence of cooling air ejection on the main flow is in the interest of scientists. In this paper experimental and numerical investigations on the trailing edge cooling air ejection at a stator profile are presented. All measurements are performed at the Straight Cascade Wind tunnel Göttingen. To verify the influence of the cooling air flow on the flow field, the velocity field is measured by Particle Image Velocimetry (PIV). The development of the cooling air concentration is analyzed by utilizing the Quantitative Light Sheet (QLS) technique. For validation purposes the QLS results are compared to CO2 concentration measurements. Both measurement techniques are in good agreement with each other. One of the most important advantages of PIV and QLS is the possibility of combining them at the same test bed due to the identical experimental setup. The experimental investigations are supported by numerical simulations based on the numerical code TRACE. Both the numerical results as well as the experimental results prove the reduction of the trailing edge shock by increasing the coolant mass flow ratio.