| Summary: | To meet market demands and yet fulfil legislation engines are now required to maintain current power levels but be more efficient at part load. Operating in this region means the turbine will be operating at low velocity ratios. This work aimed at targeting key automotive objectives which included; improving off-design performance, increasing MFR and reducing inertia, using non-conventional designs. A detailed numerical and experimental investigation of a scaled automotive VGT was carried out to better understand the flow characteristics in the blade passage. An initial study was performed at three different stator vane MFR positions to assess the impact of stator vane tip clearance location on radial turbine performance. Following this two rotor designs, one back swept, the other a splitter blade design, were simulated and tested at different stator vane positions, to ascertain their suitability at meeting automotive requirements. It was found that operating with hub side stator vane tip clearance improved efficiency by 4.5% points at the minimum MFR stator vane position. The study showed that the stator vane tip Jeak.e.ge produced a vortex which augmented the flow and improved incidence and flow development in the rotor passage. The back swept rotor design reduced the incidence angle allow values of VIC and improved efficiency by 1.3% and 2.0% points at the minimum and 25% MFR stator vane positions respectively. However, at the design point efficiency dropped by 4.4% points and MFR was reduced by 4.7%. A 5+5 splitter design improved efficiency by 1.0% point at the minimum MFR stator vane position. At the design MFR also increased by 5%. However, efficiency was seen to drop between 0.5% to 3% points at the maximum MFR stator vane position. An additional benefit of the splitter design was reduced inertia. Inertia was decreased by 3.7%.
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