Abstract
Hydro energy is a kind of typical renewable energy, which can be converted by hydraulic machinery. However, tip leakage vortex (TLV) has a significant negative influence on the flow pattern and energy performance of hydraulic machinery. In this paper, a bending shrinkage groove (BSG) is proposed to suppress the TLV and improve the energy performance of a hydrofoil first, and then a parametric optimization design method is briefly introduced and applied to determine the optimal configuration of the groove. The main geometric parameters of the groove are selected as optimized variables and three different groove configurations are selected from the optimization result. Finally, the performance improvement of the hydrofoil with groove, the sensitivity analysis of the optimization variables, and the groove impacts on the TLV and flow patterns are investigated. The results demonstrate that the preferred groove reduces the non-dimensional Q criterion vortex isosurfaces area (Qarea = 2 × 107) by 5.13% and increases the lift drag ratio by 17.02%, comparing to the origin hydrofoil. Groove depth d and groove width w are proved to have more significant impacts on the hydrofoil energy performance. The TLV and flow patterns are greatly affected by the different BSG configurations, and the wider BSG contributed to reducing the area of TLV, at the cost of energy performance deterioration.
Highlights
Hydraulic machinery with the blade tip gap is widely applied in power generation [1,2], farmland irrigation [3], waterlogging drainage, sewage treatment [4], and other similar activities [5]
Miorini et al [16] explored the internal structure of the tip leakage vortex in an axial waterjet pump and the results showed that the TLV was incepted near the blade tip around 0.2–0.3 times chord
The Pareto front, which consists of blue points, is the best trade-off solution of the optimization results, and it indicates that the two optimization targets conflict with each other, increasing the ratio R
Summary
Hydraulic machinery with the blade tip gap is widely applied in power generation [1,2], farmland irrigation [3], waterlogging drainage, sewage treatment [4], and other similar activities [5]. Much research has been carried out in the aspects of the blade tip gap effects on energy performance and TLV for hydraulic machinery. For the aspect of energy performance, Bing et al [10] found that the external characteristics of a mixed-flow pump decreased with the tip clearance increase by the experimental method. Bing et al [11] conducted the hydraulic performance test of a mixed-flow pump with different blade tip clearances and various blade angle errors and proved that the efficiency, the head, and the shaft power of the mixed-flow pump all decrease with the increase of the blade tip clearance under any flow rate.
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