**7. Conclusions**

In this paper, based on FED and CFD methods, the optimal design of WECP has been successfully conducted. Eleven schemes of experiments were designed to research the effect of experimental factors, including blade outlet width *b*2, blade outlet angle β2, and blade wrap angle ψ. A mathematical model related to the efficiency of different working conditions and the main geometric parameters of impeller was established. Meanwhile, the matching characteristics of impeller and volute were numerically studied. The results of the analysis are as follows.


**Author Contributions:** Methodology and project administration, W.L.; writing—original draft preparation and review and editing, L.J.; review and editing, W.S., L.Z., H.C. and R.K.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** The work was sponsored by the National Key R&D Program Project (No. 2017YFC0403703), National Natural Science Foundation of China (Nos. 51679111, 51409127 and 51579118), PAPD, Key R&D Program Project in Jiangsu Province (BE2016319, BE2017126), Natural Science Foundation of Jiangsu Province (Nos. BK20161472, BK20160521), Science and Technology Support Program of Changzhou (No. CE20162004), Key R&D Program Project of Zhenjiang (No. SH2017049), and Scientific Research Start Foundation Project of Jiangsu University (No. 13JDG105), Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX19\_1601).

**Conflicts of Interest:** The authors declare no conflict of interest.
