Abstract
This work analyzes the causes of the slip phenomenon in the impeller on the basis of the internal flow mechanism. Detailed optical measurements of the flow inside the rotation passages of a five-bladed centrifugal pump impeller are obtained through particle image velocimetry (PIV). On the basis of experimental data, the deviation coefficient of slip velocity is proposed and then revised according to the slip factor calculation formula of Stechkin. Results show that, at the same rotation speed, the slip factor increases with the flow rate and reaches the maximum value at 1.0 QBEP flow rate. At different rotation speeds, the slip factor increases with the rotation speed and shows a relatively large variation range. Moreover, a revised slip factor formula is proposed. The modified model is suitable for the correction of slip factor at part-load flow rates and serves as a guide for the hydraulic performance design and prediction of centrifugal pumps.
Highlights
Academic Editor: Ling Zhou is work analyzes the causes of the slip phenomenon in the impeller on the basis of the internal flow mechanism
Fujie [9] proposed the theoretical analytical formula of slip factor based on the 2D potential flow theory; Backstrom [10] put forward the hypothesis of single relative eddy (SRE), which considers that the slip factor is caused by a relative vortex within the entire impeller channel, instead of a single vortex in a single blade channel
Li [29] researched the influence of flow rate and viscosity on the slip factor of heavy oil centrifugal pump by using numerical simulation and laser doppler velocimetry (LDV) technology. e results show that the change of slip factor largely depends on the flow rate and is minimally affected by the liquid viscosity
Summary
E phase-averaged relative velocity w is the difference between the two figures, namely, the absolute velocity v and the local circumferential impeller speed u at each point, as shown in the following equation: w(x, y) v(x, y) − u(x, y). E centrifugal pump is a special volute-free structure used to obtain the flow data in the entire impeller channel. On the basis of the performance curves of the test pump, the flow rates at best effect point QBEP and head HBEP at various rotation speeds are as follows: 1.0 m3/h and 1.0 m at 600 r/ min, 1.7 m3/h and 1.5 m at 800 r/min, 1.8 m3/h and 2.67 m at 1000 r/min, 2.3 m3/h and 3.7 m at 1200 r/min, and 2.5 m3/h and 5.05 m at 1400 r/min
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