14th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Additive manufacturing (i.e., 3D printing technology) offers a great potential for many turbomachinery applications, and complex blade shapes can be easily realized by it. Especially in the case of turbines designed for organic Rankine cycle applications (ORC), this approach is rather promising since moderate temperature and pressure levels are involved. Furthermore, many ORC turbines are very compact, and sophisticated three-dimensional designs might be helpful for optimizing their aerodynamics. However, actual surface conditions and roughness behavior of printed blades can cause serious issues reagarding profile losses.The present contribution presents the outcome of an experimental intestigation of profile losses of a printed linear turbine cascade placed in the test section of a closed-loop organic vapor wind tunnel (CLOWT). This test facility at Muenster University of Applied Sciences enables the investigation of high subsonic and transonic organic vapor flows under realistic ORC turbine flow conditions at elveated pressure and temperature levels. The so-called VKI blade profile from the open literature was chosen for the cascade, and the working fluid was Novec 649. Pitot probes and hot wire anemometry were employed for measuring the flow field up- and downstream of the cascade. The inflow turbulence level was of order 0.5 %. The original roughness parameters of the printed blades were determined, and after a first set of flow measurements, the blade surfaces were further finished. After polishing manually the blades, the impact of roughness could be identified by means of a second set of flow measurements. The new organic vapor flow results were compared with literature data obtained for air and the results of computational fluid dynamics simulations.