A Behavior of the Diffuser Rotating Stall in a Low Specific Speed Mixed-Flow Pump

To study the influence of tip clearance on performance (external characteristics, pressure fluctuation and tip loss) of a low specific speed mixed-flow pump, unsteady simulation was performed for the whole flow passage with five tip clearance sizes ( δ0 = 0 mm, δ1 = 0.10 mm, δ2 = 0.25 mm, δ3 = 0.75 mm and δ4 = 1 mm). The reliability of the numerical methodology was verified in external characteristics (efficiency, head and power) and fluctuation. The performance of the pump was obtained under different discharges and tip clearance sizes using ANSYS CFX. The results showed that the variation of tip clearance size has greater effect on the external characteristics under large discharges. Meanwhile, along the flow direction, the fluctuation coefficients near the impeller shroud increase gradually with the smaller tip clearance sizes ( δ = 0.10 and 0.25 mm), while for the larger tip clearance sizes ( δ = 0.75 and 1.00 mm), the significant increase of fluctuation near the shroud of impeller inlet is closely associated with the clear leakage vortex and the large region of low pressure. Besides, with the increase of tip clearance size, the effect of tip clearance will become more remarkable under different discharge conditions. According to this study, for the optimization design of such pumps, the size of the tip clearance is suggested to be about 0.9% times the blade height at middle of the impeller passage.

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Numerical and Experimental Study of Inner Flow and Hydraulic Performance of the Mixed-Flow Pump With Low Specific Speed

Volume 3: Fluid Machinery; Erosion, Slurry, Sedimentation; Experimental, Multiscale, and Numerical Methods for Multiphase Flows; Gas-Liquid, Gas-Solid, and Liquid-Solid Flows; Performance of Multiphase Flow Systems; Micro/Nano-Fluidics ◽

10.1115/fedsm2018-83094 ◽

2018 ◽

Author(s):

Jianping Yuan ◽

Meng Fan ◽

Yanjun Li ◽

Yanxia Fu ◽

Rong Lu

Keyword(s):

Rapid Development ◽

Internal Flow ◽

Fluctuation Analysis ◽

Market Demand ◽

Mixed Flow ◽

Pump Design ◽

Flow Rates ◽

Low Specific Speed ◽

Specific Speed ◽

Flow Pump

Mixed flow pumps are very suitable for market demand with the rapid development of urbanization, especially for low specific speed mixed flow pumps which has been widely used in various fields [1–3]. In this study, the calculations of the incompressible 3D internal flow of the mixed-flow pump with low specific speed was carried out by using CFD technique based on the N-S equation coupled with the standard k-ε turbulence model at different flow rates. The hydraulic performances of the mixed-flow pump as well as the inner flow were analyzed in comparison with the corresponding experimental data. Meanwhile, the static pressure and relative velocity distribution on blades were studied at low, design as well as large flow rates, respectively. Finally, it can obtain that the predicted pump performance curves based on numerical simulation have a good agreement with the experimental results, which verify the numerical method applied in this work accurate in a certain extent. Furthermore, the results also provide some references to hydraulic forces and pressure fluctuation analysis and the performance improvement for the mixed-flow pump design.

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