**4. Conclusions**

In this paper, some near-wall region flow characteristics of impeller blades, and front and rear cover plates of a low-specific-speed centrifugal pump were studied by means of numerical simulation of the internal flow and an experiment of external characteristics. The main results are as follows:

(1) Under different flow rates from 4 m3/h to 20 m3/h, the head and efficiency from the simulations were close to the experimental results, and the simulation results were credible.

(2) Under the design flow rate, the pressure distribution of profiles on the pressure side of different blades was almost the same, as well as that on the suction side, and the static pressure on the pressure side was greater than that on the suction side. The pressure on the blade near the tongue was greatly affected by the separator flow. The pressure of profiles at the distance of 2 mm from the blade pressure side was greater than that of profiles at the distance of 0.5 mm from the blade pressure side, but the pressure of profiles at the distance of 2 mm from the blade suction side was less than that of profiles at the distance of 0.5 mm from the blade suction side. With the increasing of the flow rate, the pressure on the pressure side did not decrease significantly, but the pressure on the suction side decreased more obviously.

(3) Under the design flow rate, the relative velocity distribution of profiles on the pressure side of different blades was almost the same, as well as that on the suction side; it started from the forward flow near the impeller inlet, decelerated or even formed counter-currents, and accelerated again. The relative velocity achieved its maximum in a certain range of the inlet area on the suction side, and then suddenly decreased, but there was no countercurrent in general. With an increasing flow rate, the relative velocity difference between the suction side and the pressure side increased obviously, and there was a countercurrent on the pressure side within the range of radii from 40 mm to 50 mm when the flow rate was 13 m3/h or 20 m3/h.

(4) Under three flow rates of 7 m3/h, 13 m3/h, and 20 m3/h, the cross-flow velocity was relatively different. The greater the flow rate was, the greater the turbulent kinetic energy on the pressure side was. The turbulent kinetic energy on the suction sides was larger than that on the pressure side.

**Author Contributions:** W.C. designed the pump, simulated and analyzed data, organized paper; Z.J. contributed meshes construction and simulation assistance; Q.Z. contributed experimental process and experimental results analysis.

**Funding:** This work was supported by the National Key R&D Program of China (2018YFC0810506) and the Key R&D Program of Zhenjiang (SH2017049, BK20161472).

**Conflicts of Interest:** The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

#### **References**


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