ADDITIVE MANUFACTURING FOR FAST PROTOTYPING OF A VELOCITY COMPOUNDED RADIAL RE-ENTRY TURBINE

Abstract

In order to achieve a drastic reduction in CO2 emissions to limit global warming, it must be possible to globally cover the electricity demand from renewable sources. However, the fluctuating availability of solar and wind energy will nevertheless make it necessary to complement the renewables by thermal power plants. Additionally using e.g., the potentials of waste, biomass or waste heat from industrial processes locally in Organic Rankine Cycle (ORC) power plants is a promising approach to finally achieve a stable and sustainable electricity supply. In the present work, therefore, different variants of a radial, velocity compounded re-entry cantilever turbine (Elektra turbine) are investigated regarding their potential for such applications. The paper concentrates on the fast prototyping of an existing 5 kW air turbine demonstrator, recently developed by the authors, by using the possibilities of additive manufacturing with plastic materials to substitute essential parts of the flow geometry. In this context the approach to implement the plastic parts in the turbine is explained. Experimentally determined efficiency parameters of various 3D-printed deflection channel modifications and a printed plastic wheel made of PA12GB are presented, discussed, and compared to the fully milled metal turbine. This results in a quantification of the additional losses due to the higher inaccuracies and roughness of the printed parts, which can be taken into account in further investigations. Furthermore, the various problems and hurdles that must be observed when using 3D-printed plastic parts in high-speed turbomachines are highlighted. With regard to the rotor wheel, the authors conclude that the use of additively manufactured plastic wheels is only feasible with increased preliminary testing. The time required for this is usually not in proportion to the manufacturing time and costs saved. For the stator parts however, 3D-printing turned out to be a reasonable approach.