# Experimental Analysis on Pressure Fluctuation Characteristics of a Centrifugal Pump with Vaned-Diffuser

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## Abstract

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## 1. Introduction

## 2. Experiment Bench

#### 2.1. A Centrifugal Pump with a Vaned-Diffuser

_{d}) was 270 m

^{3}/h, head of the pump (H

_{d}) was 15 m, rotation speed (n) was 1450 r/min and specific speed (${n}_{s}=\frac{3.65n\sqrt{Q}}{{H}^{3/4}}$) was 190. What is depicted in Figure 1 is the schematic diagram of the pump with a vaned-diffuser. The main parts were the pump body, impeller vaned-diffuser, pump shaft and pump cover.

#### 2.2. Testing Bench

#### 2.3. Location of Monitoring Points

- (1)
- 10 monitoring points P1–P10 were set on the pump chamber. Since the PF near the outlet of the pump is more complex, two monitoring points P7 and P9 were added near that zone.
- (2)
- Rotor-stator interference between the impeller and the vaned-diffuser and fluid turbulence flowing into the pump body will result in unsteady flow. So, 16 monitoring points, P11–P26, were set around the outer section of the pump body. These 16 monitoring points were divided into two circles. P19–P26 were located on the plane of the center line of the diffuser and the impeller. P11–P18 were in the symmetrical plane centered on the center line of the annular chamber of the pump body.
- (3)
- Pressure fluctuation near the outlet of the pump was larger, therefore we set up four monitoring points, P27–P30, uniformly around the outlet pipe.

## 3. Results Analysis

#### 3.1. External Characteristics Analysis of the Pump

#### 3.2. Measurement Results and Analysis of Pressure Fluctuation

#### 3.2.1. Measurement Results and Analysis at P1–P10

_{d}to 0.6Q

_{d}, the amplitude of PF at P1–P10 decreased gradually and the difference among every point became less. At the lower flow rates, the amplitude of PF at every monitoring point was larger. At 0.2Q

_{d}, the amplitude of PF was the largest. As the flow rate continued to increase from 0.6Q

_{d}to 1.2Q

_{d}, the overall trend of amplitudes of PF gradually diminished. At the design flow rate, amplitude difference between the monitoring points was the largest. The maximum difference was 2.85 kPa.

#### 3.2.2. Measurement Outcomes and Analysis at P11–P26

_{d}–1.3Q

_{d}, except P12, P13 and P15, the remaining monitoring points amplitude of PF rose slightly. The variation of amplitude of PF at P11–P18 was generally larger than P19–P26. From P11–P18, the greatest amplitude difference of PF was at P17 (73.68%). The greatest amplitude of PF was at P17 (10.73 kPa) under 0.2Q

_{d}. Among P19–P26, the greatest amplitude difference of PF was at P20 (71.78%). The greatest amplitude of PF was at P25 (9.34 kPa), which was 12.95% less than P17. At the design flow rate, the amplitude of PF at each monitoring point was P16 > P15 > P14 > P13 > P12 > P17 > P11 > P18, P25 > P21 > P26 > P24 > P23 > P22 > P20 > P19 in order of the amplitude size. Affected by the unsteady flow of the pump outlet, amplitudes of PF at all these monitoring points near the outlet pipe of the pump were larger. The largest difference of PF was 26.89%.

#### 3.2.3. Measurement Results and Analysis at P27–P30

_{d}–1.0Q

_{d}. Then at 1.2Q

_{d}–1.3Q

_{d}, P27, P29 and P30 amplitudes of the PF presents rose steeply.

#### 3.2.4. Analysis of Time and Frequency Distribution at Typical Measuring Points

## 4. Conclusions

- (1)
- The head of the pump with vaned-diffuser at the design flow rate reached 15.03 m, and the efficiency value of the pump with a vaned-diffuser at the design flow rate reached 71.47%.
- (2)
- Pressure fluctuation decreased gradually with the increasing distance from the impeller outlet. As the flow rate increased, the amplitude of PF decreased. It reached a minimum value at 1.0Q
_{d}or 1.2Q_{d}and then increased as the flow continued to increase. The amplitude of pressure fluctuation around the pump diffusion segment was larger. - (3)
- The variation of pressure fluctuation at P1–P10 followed the same trend. However, there were some wide frequency bands with different frequencies.
- (4)
- The dominant frequency of pressure fluctuation was the blade passing frequency and the main signal source of pressure fluctuation was from the rotor-stator interference, which was influenced from both the impeller and vaned-diffuser.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 2.**Component structure parts: (

**a**) 3-D models of vaned-diffuser; (

**b**) 3-D models of impeller and (

**c**) actual component parts.

**Figure 7.**Time and frequency d graphs of PF at P1–P10 under the design flow rate: (

**a**) time vs. pressure and (

**b**) frequency vs. amplitude of pressure fluctuations.

**Figure 8.**Comparison of the amplitude of pressure fluctuation at P11–P26: (

**a**) P11–P18 and (

**b**) P19–P26.

**Figure 9.**Time and frequency distribution of PF at P11–P26: (

**a**) time of PF at P11–P18; (

**b**) frequency of PF at P11–P18; (

**c**) time of PF at P19–P26; and (

**d**) frequency of PF at P19–P26.

**Figure 11.**Time and frequency distribution of PF at P27–P30: (

**a**) time vs. pressure and (

**b**) frequency vs. amplitude of PF.

**Figure 12.**Time and frequency distribution diagram of PF at P28: (

**a**) time vs. pressure and (

**b**) frequency vs. amplitude of PF.

Category | Scope of Measurement | Output Signal | Precision | Operating Temperature |
---|---|---|---|---|

Parameter | 0–1 Mpa | 4–20 mA | 0.25% FS | −10–80 °C |

Parameter | Flow Rate | Head | Speed | Pressure Fluctuations |
---|---|---|---|---|

Random uncertainty | ±0.03 | ±0.03 | ±0.02 | ±0.20 |

Systematic uncertainty | ±0.21 | ±0.22 | ±0.10 | ±0.12 |

Uncertainty | ±0.21 | ±0.22 | ±0.10 | ±0.24 |

Standard | ±2.00 | ±1.5 | ±0.40 | ±3.6 |

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**MDPI and ACS Style**

Liu, H.; Xia, R.; Wang, K.; Jing, Y.; He, X.
Experimental Analysis on Pressure Fluctuation Characteristics of a Centrifugal Pump with Vaned-Diffuser. *Water* **2020**, *12*, 126.
https://doi.org/10.3390/w12010126

**AMA Style**

Liu H, Xia R, Wang K, Jing Y, He X.
Experimental Analysis on Pressure Fluctuation Characteristics of a Centrifugal Pump with Vaned-Diffuser. *Water*. 2020; 12(1):126.
https://doi.org/10.3390/w12010126

**Chicago/Turabian Style**

Liu, Houlin, Ruichao Xia, Kai Wang, Yucheng Jing, and Xianghui He.
2020. "Experimental Analysis on Pressure Fluctuation Characteristics of a Centrifugal Pump with Vaned-Diffuser" *Water* 12, no. 1: 126.
https://doi.org/10.3390/w12010126