Development of Particle Image Velocimetry for a High Speed Two-Stage Turbine

Turbine efficiency is a primary metric for categorizing turbine performance. Efficiency is an integral measurement that requires mass flow averaged values; therefore, the flow velocity components are required both upstream and downstream of the turbine. A standard method to determine the flow velocity components involves using aerodynamic probes, which require at least four-hole pressure measurements in highly three-dimensional flows. Alas, in high-speed small-core turbines, the insertion of a pressure probe into a relatively small turbine outlet region induces significant blockage, resulting in a flow distortion, increasing the measured total pressure, and altering the flow angles compared to the no-probe conditions. Therefore, an optical non-intrusive measurement technique such as Particle Image Velocimetry (PIV) is proposed in this thesis. To conduct PIV in a small-core turbine, a further downstream laser delivery device must be developed for the specific test rig in question, as well as utilizing a practical means of image acquisition. An endoscopic PIV device, coupled with a borescope camera, is my proposed solution and the first subject of my thesis dissertation. A second problem in a small core turbine is the existence of large areas of separated flows caused by massive secondary flows. In flow-separated regions, the main problem is the poor seeding of particles. Therefore, in the second part of my thesis, I propose using local seeding; my approach was experimentally demonstrated in a linear test section, where the high-speed turbine flow is replicated using a one-feet large 3D hump, enabling the comparison of PIV with other techniques and Computational Fluid Dynamics (CFD). The giant separation bubble was characterized by collecting data within the shear layer and the separated region. The two proposed developments pave the way for the future implementation of PIV in the two-stage high-speed turbine owned by the Purdue Experimental Turbine Aerothermal Lab (PETAL).