Design of a Measurement System to determine Cooling Effectiveness on a rotating Turbine rig using Pressure Sensitive Paint

Abstract

Film cooling is widely used to protect gas turbine blades and vanes from the extremelly hot gases leaving the combustion chamber. Over the past decades, film cooling on blades, vanes and end-wall has been widely studied. In order to understand and define the process several measurement techniques have been developed. Given that numerical simulations are yet not accurate enough, as they are not able to take into account all the parameters that affect such process, the interest in experimental measurements has grown. Several measurement techniques have been used in order to calculate the film cooling effectiveness and being able to understand how the different variables affect to the overall efficiency of the process. Trying to determine film cooling efectiveness, Pressure Sensitive Paints (PSP) have been recently adapted and used. PSP have been developed since 1980s for different fluid mechanics and aerodynamic testing expermients. Since 1990s the technique is mature enough to be used and achieve high quality results in industrial wind tunnels. PSP is an absolute transducer able to convert units of surface pressure into units of light. PSP systems are able to give high precision measurements with full-surface coberture and high resolution. As PSP is a non-intrusive measurement technique, once it is designed it can be relatively easy adapted to new systems. This Master Thesis focuses on PSP technique, and aims to give a global explanation of the technique as well as a clear and precise definition of each part of the process. The main goal for this project is to design, build and test a PSP system. In order to test the PSP system, a test setup has been design, consisting in a flat test plate with cooling holes. The design of the process has been thought to be tested in the small Wind tunnel owned by the department Gasturbinen, Luft- und Raumfahrtantriebe (GLR) in the Technische Universität am Darmstadt (TUD). Although the long term objective is to adapt such system to other facilites owned by the same department such as the High Reynold Number Turbine (HiReNT) or the Large Scale Turbine Rig (LSTR).