Unstable flow analysis of transient process in the pump as turbine during turbine mode caused by pump power failure DOI
Chenying Zhang, Giorgio Pavesi, Ji Pei

et al.

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(11)

Published: Nov. 1, 2024

Mixed-flow pump as turbines (PATs) serve pivotal components within energy micro-grids, facilitating conversion and storage. However, the emergence of pressure pulsations in these systems can markedly affect their stability efficiency, especially power failure. To simulate power-off transition accurately, commercial computational fluid dynamics code ANSYS CFX® is integrated by a Fortran program through parametric design language transient simulation to enable real-time iterative calculations angular momentum equations for mixed-flow PAT at varying speeds. This study integrates analysis radial forces, vortices, flow lines elucidate sudden changes observed during stages. Specifically, significant fluctuations amplitude volute tongue were found various initial rates, which correlated closely with forces. The increase nonuniform distribution forces emerged main factors fluctuations. In addition, reveals that intensity evidenced wavelet time-frequency on surface blade significantly exceeds back blade. Furthermore, characteristics inside draft tube, pulsation signals are mainly concentrated low-frequency region accompanied presence double-helix structure. These results provide an important reference further understanding operating mechanism turbine, helps optimize improve performance.

Language: Английский

Transient rear cavity vortex flow in a spherical-casing nuclear reactor coolant pump DOI
Dan Ni,

Hongchi Zhong,

Bo Gao

et al.

Physics of Fluids, Journal Year: 2025, Volume and Issue: 37(3)

Published: March 1, 2025

The next-generation nuclear reactor coolant pumps (NRCP) have gradually transitioned to mixed-flow designs due their advantages of a wide operating range, broad flow and high efficiency. These often adopt unconventional spherical casings, resulting in complex internal dynamics. Therefore, comprehensive analysis NRCPs' field structure is critical for evaluating operational stability. This investigation uses large eddy simulation analyze the transient inside casing NRCP. A new type large-scale strip-like vortex rear cavity has been found, named vortex, its pressure pulsation characteristic analyzed. three stages. identifies 7.09 Hz as frequency recognized self-rotation frequency. Additionally, 24.82 identified front shedding. results this indicate that optimizing geometric design might help weaken intensity thereby mitigating impact on stability provides valuable guidance improving efficiency reliability

Language: Английский

Citations

1
Rotational speed modulated air–cavitation interactions in centrifugal pumps DOI
Fanjie Deng, Jianping Yuan, Peng Wang

et al.

Physics of Fluids, Journal Year: 2025, Volume and Issue: 37(4)

Published: April 1, 2025

The high-power consumption and excessive heat generation in data centers present challenges to thermal management. As a critical component of liquid cooling systems, the circulation pump's stability reliability are directly impacted by cavitation air entrainment, which degrade performance. This study investigates effects with entrained under various rotational speeds volume fractions on centrifugal pump performance, pressure pulsation, behavior. Experiments were conducted using closed-loop test rig at three (2900, 2300, 1800 r/min). impact different time-domain frequency-domain characteristics pulsations was systematically analyzed. results reveal that: (1) maximum efficiency entrainment conditions exceeds that natural cavitation. condition optimizes distribution within impeller channels, particularly near outlet. (2) Air effectively suppresses high-amplitude fluctuations caused collapse, especially high fraction (1.6%), varying observed during stage depending fractions. (3) ratio speed bubble determines characteristics, manifesting as combination blade frequency, broadband, low-frequency signals, influencing flow field energy distribution. (4) Cavitation air–cavitation interference frequencies cluster around St = 6, indicating aggregation, fragmentation rotation, distinct interaction patterns speeds. provides novel theoretical explanation mechanisms aggregation induce instability low-speed conditions.

Language: Английский

Citations

0
Multi-Condition Hydraulic Performance Enhancement for a Mixed Flow Pump through Improved AIGV DOI
Yunhao Zheng, Yanjun Li, Fan Zhang

et al.

Energy, Journal Year: 2025, Volume and Issue: unknown, P. 136319 - 136319

Published: April 1, 2025

Language: Английский

Citations

0
Research on the energy characteristics of the turning region in the cavitation performance curve of an axial flow pump based on energy flow density and entropy production DOI Creative Commons
Lei Yu, Li Cheng,

Weigao Sheng

et al.

Engineering Applications of Computational Fluid Mechanics, Journal Year: 2025, Volume and Issue: 19(1)

Published: May 12, 2025

Language: Английский

Citations

0
Effect of free and compound vortex designs on the energy characteristics and operational stability of mixed flow pumps DOI
Mengcheng Wang, Songshan Chen, Yandong Gu

et al.

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(8)

Published: Aug. 1, 2024

The effectiveness of the inverse design method has been widely proven in previous studies, but research on effect different vortex designs performance mixed flow pumps is relatively scarce. In this paper, performances models I1 and I2, which were designed with free compound designs, respectively, are compared to study energy characteristics operational stability pumps. results show that efficiency at 0.8Qdes, 1.0Qdes, 1.2Qdes improved by 0.54%, 0.95%, 5.91%, design, velocity pressure pulsations under conditions also significantly reduced. internal analysis shows increased mainly related reduction local entropy production from hub mid-span wall shroud within diffuser due improvement jet-wake structure near hub. suppression low-momentum fluid aggregation H-S secondary caused increase axial spanwise uniformity total pressure.

Language: Английский

Citations

2
Experimental and numerical investigation on the cavitation erosion effect and resonance effect of submerged water jets DOI

Jincheng Hu,

Yong Kang,

Hanqing Shi

et al.

Ships and Offshore Structures, Journal Year: 2024, Volume and Issue: unknown, P. 1 - 13

Published: Nov. 4, 2024

To analyse the cavitation erosion effect and resonance of submerged water jets generated by organ-pipe nozzles, experimental numerical research is conducted in nozzles with five different diffuser angles. The intensity flow characteristics are obtained test, high-speed photography Large Eddy Simulation. results illustrate that nozzle a 60° angle capable producing strong effect. Compared to fully developed jet, axial pressure oscillation axially confined stronger, indicating it has stress wave modulates after reflection from impact wall. This modulation excitation original main frequency jets, which then gives rise multiple oscillations, thereby forming

Language: Английский

Citations

1
Unstable flow analysis of transient process in the pump as turbine during turbine mode caused by pump power failure DOI
Chenying Zhang, Giorgio Pavesi, Ji Pei

et al.

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(11)

Published: Nov. 1, 2024

Mixed-flow pump as turbines (PATs) serve pivotal components within energy micro-grids, facilitating conversion and storage. However, the emergence of pressure pulsations in these systems can markedly affect their stability efficiency, especially power failure. To simulate power-off transition accurately, commercial computational fluid dynamics code ANSYS CFX® is integrated by a Fortran program through parametric design language transient simulation to enable real-time iterative calculations angular momentum equations for mixed-flow PAT at varying speeds. This study integrates analysis radial forces, vortices, flow lines elucidate sudden changes observed during stages. Specifically, significant fluctuations amplitude volute tongue were found various initial rates, which correlated closely with forces. The increase nonuniform distribution forces emerged main factors fluctuations. In addition, reveals that intensity evidenced wavelet time-frequency on surface blade significantly exceeds back blade. Furthermore, characteristics inside draft tube, pulsation signals are mainly concentrated low-frequency region accompanied presence double-helix structure. These results provide an important reference further understanding operating mechanism turbine, helps optimize improve performance.

Language: Английский

Citations

1