Basic CFD models to support the re-design of a radial micro-turbine for energy harvesting

This paper presents the numerical and experimental validation of CFD models having different complexity and developed to study a radial inflow micro-turbine prototype designed for energy harvesting from compressed gases pipelines. The single stage radial turbine was experimentally tested under compressed air operation at pressure ratios between 1.04 and 2.1 and rotational speed in the range 70000-150000rpm. The open-source CFD code MULTALL was used to generate and run both the 2D through-flow and the fully 3D steady-state RANS models. A special geometry has been conceived to adapt the spiral casing of the actual prototype to the modelling capabilities of the CFD code. The results of the 2D and 3D simulations have been experimentally validated in terms of normalized performance maps, suggesting MULTALL as a viable CFD tool to support the future re-design of the radial micro-turbine. In particular, the low computation time required by the through-flow simulations (few minutes when performed on a standard laptop computer) and their satisfactory level of accuracy (if compared with the fully 3D simulations) suggest that the 2D model allowed by the capabilities of MULTALL permits fast indications reliable enough to be best suited to the early stage of the radial micro-turbines design.