---

As pumps are used frequently in industrial plants, their performance improvement is important. In this study, performance improvement of centrifugal pumps by application of splitter blades have been investigated both numerically and experimentally. Radial impellers with different length of splitter blades have been manufactured and tested to obtain performance charts. On the other hand, the flow in impeller and volute has been investigated numerically by ANSYS-CFX commercial code. Numerical study has been done using Finite volume method and k-ωSST turbulence model. Rotating and stationary frames have been used to analyze flow in impeller and volute respectively and the results have been coupled by Frozen Rotor. Three impellers with the lengths of splitter blades equal to 0, 33% and 66% of original blades were tested. Results show head increase when the splitter blades added while the amount of increase depends on the splitter blades length. At BEP (Best Efficiency Point) the maximum head increase was reported for impeller type three (the length of splitters equal to 66% of original blades) about 10.5 percent. It should be noted that as the capacity tends to BEP, the effect of splitter blades is more significant.

---

Regenerative pumps are pumps with a very low specific speed. The main characteristic of regenerative pumps is the ability to produce high heads at low flow rates.  In this article, numerical and experimental methods have been used to analyze and improve the performance of regenerative pumps and also to investigate the effect of leakage flow around the impeller. In order to validate, an experimental test circuit of regenerative pumps has been designed and built. The comparison of the numerical and experimental results have a good agreement, which indicates the high accuracy of the numerical simulation. Based on the results of the study, we conclude that increasing the geometric thickness of the leak leads to an increase in mixing the high-pressure fluid of the outlet nozzle with the low-pressure fluid of the inlet area, leading to a decrease in the generating head generated by the regenerative pump. The performance parameter of efficiency will also decrease significantly by increasing the geometric thickness of the leakage to 0.4 mm compared to the original geometry with a leakage of 0.26 mm. On the other hand, reducing the leakage thickness to 0.2 mm will lead to the improvement of the functional parameters of the head and the efficiency of the reproducing pump. Also, the ideal geometry without leakage has been introduced and calculated for the maximum and theoretical limit of head and efficiency parameters.