Numerical Analysis Of The Interior Flow And Caricateristc On Axial Flow Pump With Tip Clearance

The value of axial flow pump's tip clearance, the shape of blade tip and the flow in the blade tip clearance have great influence on the efficiency of axial flow pump and even affect its running.First, select the product of submersible axial flow pump ZQ2870C-4 as the study object. And get seven kinds of pump models with different tip clearance gap width by changing the diameter of the pump casing. The value of tip clearance is as follow:0mm, 0.65mm, 1mm, 1.5mm, 2mm, 3mm , 5mm. The standard k-e turbulence model and SIMPLE algorithm are applied to analyze the flow passage of the pump at design condition (Q=1.85m³/s,H=9.19m,n=735r/min) under different schemes by FLUENT6.1 in this thesis. The result indicates that: 1) The tip clearance flow has great influence on the surface of suction and blade tip; 2) The center of low pressure in the tip area moves to the outlet of the pump through the blade tip with the tip clearance enhance; 3) Axial velocity distribution shows that the tip clearance leakage flow is asymmetric and the worst leakage flow area is at 15%-20% chord of the blade tip; 4) The analysis on the flow of axial plan indicates the development of leakage vortex. And when the clearance gap width reaches to 5mm(0.77%D2) there appears vortex in the tip clearance; 5) The head and hydraulic efficiency are forecasted and the results indicate that the head and hydraulic efficiency decline with the tip clearance enhancing. But the head and hydraulic efficiency don't decline too much when the tip clearance is not large than 1.5mm(0.23%D₂) . So the tip clearance is suggested not larger than 0.23%D₂ which is a little big than the value recommended in the design manual.Then, the submersible axial flow pump with tip clearance of 1.5mm is adopted to study the interior flow by smoothing the blade tip. According to the experience four kinds of smoothing schemes are adopted. The smoothing radius includes double of the tip clearance width, half of the blade flange thickness and two-thirds of the blade flange thickness. The results indicate that smoothing the pressure side flange can improve the tip clearance flow condition and reduce the property of gap cavitation. And under this scheme the hydraulic efficiency is the best. So the best smoothing scheme is choosing the double thickness of the tip clearance width to smooth the pressure side of the blade.This pump's head at different flowrates are calculated to analyze the veracity ofnumerical simulation. It is found that the error is less than 6% compared with the experiment results under 0.8-1.2Q_d (design flowrate). This result indicates the result of numerical simulation is acceptable.