# Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement

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## Abstract

**:**

## 1. Introduction

## 2. Research Objective

_{d}was 0.83 m

^{3}/s, the design head H

_{d}was 143.4 m, the rotational speed n

_{d}was 990 r/min, and the fluid medium was 25 °C liquid water. The specific speed n

_{q}of the double-suction centrifugal pump was calculated according to the following formula for comparison between similar pump designs [17]:

_{q}and c

_{h}are the special coefficient of flow rate and head. For the double-suction pump, c

_{q}is 2. For the two-stage pump, c

_{h}is 2. In this case, the value of n

_{q}is 25.9.

## 3. Setup of Improvement Design

#### 3.1. Design Target

_{out}and P

_{in}represent the total pressure at the pump outlet and the pump inlet, respectively, including the sum of static and dynamic pressures; M is the torque of the impeller around the axis of rotation of the impeller; and ω is the rotational speed of the impeller.

#### 3.2. CFD Setup

_{1}is the blending function. σ

_{k}and σ

_{ω}are constants of the turbulence model. l

_{k}

_{-}

_{ω}is the parameter for evaluating the turbulence scale, which can be written as l

_{k}

_{-}

_{ω}= k

^{1/2}β

_{k}ω, and β

_{k}is also the model constant.

#### 3.3. Performance Evaluation

^{3}/s, which were not at a high level. At Q = 0.715 m

^{3}/s, the efficiencies of the two stages were 92.5% and 91.3%, which were also not high enough. Therefore, this two-stage double-suction centrifugal pump still has significant margin for improvement. Figure 4 also provides the proportion of first and second stage of impellers in terms of capacity. This represents the pressurization performance of the two-stage impeller under different flow rate conditions. At small flow rate, the second-stage impeller has higher capacity. At middle flow rate, the two stages are equal. At large flow rate, the first-stage impeller has higher capacity. This provides assistance for optimizing and improving the matching of flow channels.

## 4. Improvement History

## 5. Comparative Analysis

#### 5.1. Geometry Comparison

#### 5.2. Performance Comparison

#### 5.3. Flow Pattern Comparison

^{3}/s were both considered. The streamlines are used as the main comparative object to reflect the distribution of vortexes, secondary flow, and the quality of flow patterns, helping to reveal the reasons for performance differences. The streamline is colored with the magnitude of velocity, reflecting the magnitude of local flow velocity and also representing the uniformity of flow to a certain extent.

^{3}/s.

^{3}/s. However, compared with the initial solution, the flow pattern in the volute was greatly improved at Q = 0.953 m

^{3}/s. The large-scale vortex was eliminated. The non-uniformity of the relative velocity became weaker. Flow near the first and second impeller outlets became much more uniform. This is why the efficiency became much higher and the high-efficiency range became wider after improvement. The head of the pump rose when the loss became lower. The overall operating efficiency and stability of the pump were positively improved.

## 6. Experimental–Numerical Verification

## 7. Conclusions

- (1)
- The process of improving a pump design is mainly through the judgment of CFD on flow and pump performance and through constantly modifying the design scheme. In this study, a total of 39 improvements were made to the two-stage double-suction centrifugal pump. The efficiency of the pump increased with fluctuations in the 39 improvements, until the performance of the pump finally met the design requirements. This proved that the improvement was feasible.
- (2)
- By comparing the geometry, performance, and flow pattern of the original scheme and the final scheme of the two-stage double-suction centrifugal pump, the geometry of the final scheme was shown to be more suitable for the operating conditions, the internal flow was more stable, and the performance was significantly improved. After improvement, the pump head was increased by 10~15 m, and the efficiency was increased by 4~9% within the operation range.
- (3)
- To achieve this improvement, all the components except the semi-spiral suction chamber were modified for a better performance. The inlet division section was modified by adding a baffle at the fork. The trailing-edge blade angle of the first- and second-stage impellers were increased to a higher head. The section area of the inter-stage channel was reduced because the initial areas were too large, with vortexes and flow separation. The volute section area was increased to reduce the friction loss because of the insufficient area in the original. The hydraulic losses were reduced from about 14% to less than 6% after modification.

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 3.**Performance evaluation of the initial design solution. (

**a**) Q-H performance; (

**b**) Q-η performance.

**Figure 4.**Hydraulic loss of different components in the initial solution (three off-design points) and the capacity proportion of the first- and second-stage impellers in the initial plan.

**Figure 6.**Performance change history of three operating points during the improvement process. (

**a**) Head; (

**b**) efficiency.

**Figure 8.**Comparison of the details of the changed components before and after improvement. (

**a**) Inlet division section; (

**b**) first-stage impeller; (

**c**) inter-stage channel; (

**d**) second-stage impeller; (

**e**) volute.

**Figure 10.**Hydraulic loss of different components in the final solution (three off-design points) and the capacity proportion of the first- and second-stage impellers.

**Figure 11.**Flow pattern (streamlines) in the components of the initial solution under small flow rate and large flow rate conditions. (1) Total; (2) first impeller; (3) inter-stage channel; (4) second impeller; (5) volute. (

**a**) Q = 0.572 m

^{3}/s; (

**b**) Q = 0.953 m

^{3}/s.

**Figure 12.**Flow pattern (streamlines) in the components of the final solution under small flow rate and large flow rate conditions. (1) Total; (2) first impeller; (3) inter-stage channel; (4) second impeller; (5) volute. (

**a**) Q = 0.572 m

^{3}/s; (

**b**) Q = 0.953 m

^{3}/s.

Relative Flow Rate Point | Flow Rate (m^{3}/s) | Head Requirement (m) | Efficiency Requirement (%) |
---|---|---|---|

0.30 | 0.250 | 171.0 | - |

0.65 | 0.537 | 158.1 | 80.0 |

0.86 | 0.715 | 143.4 | 84.5 |

1.00 | 0.830 | 132.7 | 82.5 |

1.15 | 0.953 | 113.6 | 81.0 |

Component | Inlet Division Section | Semi-Spiral Suction Chambers | First-Stage Impellers | Inter-Stage Channels | Second-Stage Impeller | Volute | Total |
---|---|---|---|---|---|---|---|

Mesh Node Number | 227,143 | 1,061,812 | 279,590 | 794,134 | 317,946 | 558,224 | 3,238,849 |

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## Share and Cite

**MDPI and ACS Style**

Zhu, D.; Hu, Z.; Chen, Y.; Wang, C.; Yang, Y.; Lu, J.; Song, X.; Tao, R.; Wang, Z.; Ma, W.
Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement. *Water* **2023**, *15*, 1785.
https://doi.org/10.3390/w15091785

**AMA Style**

Zhu D, Hu Z, Chen Y, Wang C, Yang Y, Lu J, Song X, Tao R, Wang Z, Ma W.
Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement. *Water*. 2023; 15(9):1785.
https://doi.org/10.3390/w15091785

**Chicago/Turabian Style**

Zhu, Di, Zilong Hu, Yan Chen, Chao Wang, Youchao Yang, Jiahao Lu, Xijie Song, Ran Tao, Zhengwei Wang, and Wensheng Ma.
2023. "Improvement Design of a Two-Stage Double-Suction Centrifugal Pump for Wide-Range Efficiency Enhancement" *Water* 15, no. 9: 1785.
https://doi.org/10.3390/w15091785