Vortex motion in vaneless space and runner passage of pump-turbine in S-shaped region

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(2)

Published: Feb. 1, 2024

This study examines the S-characteristic, a key factor affecting safe grid connection and operation of pumped-storage units, its significant impact on safety power stations. We conducted numerical simulations model experiments to investigate vortex motion characteristics in vaneless space runner passage pump-turbines operating within S-shaped region, along with an analysis pressure pulsation characteristics. The accuracy these was validated through laser Doppler velocimetry experiments, particle image were used capture space. observed that vortices generated guide vane side follow flow direction, blocking passage, while those by blades move opposite direction. Employing entropy production theory Liutex method, we investigated distribution hydraulic loss region. results show reduced rates lead area, which become main contributors energy this These vortices, mainly arise from separation blade surfaces due suboptimal inflow conditions. also identifies fluctuations space, induced rotating stall, as most phenomenon, significantly impacts performance unit both upstream downstream directions.

Language: Английский

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Study on suppression of cavitating vortex rope on pump-turbines by J-groove

Applied Energy, Journal Year: 2024, Volume and Issue: 360, P. 122843 - 122843

Published: Feb. 15, 2024

Language: Английский

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Rotor–stator interaction investigations in variable speed reversible pump-turbine at higher head

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(3)

Published: March 1, 2024

Efficiency and grid stability can be improved by variable speed operation using doubly fed induction machine technology for pumped storage plants experiencing significant head variations. With the higher penetration of intermittent renewable energy sources, viz., solar wind, may stabilized operating reversible pump-turbines (RPTs) in off-design conditions. In a turbine mode, RPT is more susceptible to fatigue vibrations when at as result hydraulic instability generated rotor–stator interaction (RSI); therefore, its performance becomes even critical. The powerhouse structural components, including floors columns, could experience intense because this instability. Therefore, it essential investigate RSI RPTs head. These investigations present results numerical analysis associated pressure fluctuations high-head scaled model was used, simulations were executed utilizing shear stress transport k-ω turbulence model. performed best efficiency point conditions having optimized rotational speed. show that main source all RSI, where dominant frequencies are blade passing frequency (9fn) harmonics. It also found lowers RPT.

Language: Английский

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Investigation on the characteristics and formation mechanism of backflow in S-shaped region of a reversible pump-turbine

Physics of Fluids, Journal Year: 2025, Volume and Issue: 37(2)

Published: Feb. 1, 2025

When reversible pump turbines go through the S-shape region, there is some significant backflow regions in vaneless space, accompanied by severe pressure fluctuation. However, internal correlation and mutual influence mechanism among fluctuation, turbulent vortex structure, are still unclear enough current research. In this work, characteristics formation of turbine region figured out using computational fluid dynamics methods. The results indicate that Leading-Edge-Passage-Vortex caused adverse gradient dominant initial stage backflow. stage, interaction between inflow main reason causing high amplitude wideband fluctuation components space. development, centrifugal force play roles different regions, respectively. rotating stall phenomenon appears runner a low-frequency component 0.6fn 0.3fn∼0.45fn appeared, respectively, space runner. fully developed dominated concentrated flow area inlet, while pushed to upper crown lower ring. These findings can provide theoretical supports for improving stability operating off-design condition.

Language: Английский

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Study on cavitating vortex rope characteristics of reversible pump-turbine under part load turbine condition

Physics of Fluids, Journal Year: 2023, Volume and Issue: 35(8)

Published: Aug. 1, 2023

Pressure fluctuations in the draft tube mainly arise from rotational motion of vortex rope. The formation and development rope are significantly influenced by cavitation. However, precise mechanism underlying progression cavitation its initial weak state to a more severe level remains unclear. objective this study is investigate pump-turbine operating under part load turbine conditions. Numerical simulations were conducted analyze impact coefficient on various parameters, including vapor volume, efficiency, head. With increasing degree cavitation, rope's pattern undergoes transition helical type torch-like type. This consequently leads shift dominant frequency pressure within tube. Furthermore, exhibits higher speed compared rope, thereby causing pronounced effect field. factors contributing morphological explored, with particular emphasis accelerating reverse axial flow reduction tube's circumferential velocity. Additionally, examined swirl number pattern, while also assessing entropy production. These findings provide valuable insight into control pump-turbines Moreover, they carry significant implications for design optimization systems.

Language: Английский

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Research on pressure pulsation characteristics of a pump-turbine in pump mode with rotating stall: Focus on the broadband frequency

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(4)

Published: April 1, 2024

To investigate the adverse effects of rotating stalls on pressure pulsation characteristics a pump-turbine in pump mode, an unsteady numerical simulation was carried out by applying partially averaged Navier–Stokes turbulence model. The methods were carefully verified, and onset flow rate hump at performance curve heads good agreement with experimental data. stall appeared guide vane when ranged from 0.514 to 0.887 times best efficiency point (QBEP), frequency 11.7% rotational frequency. In period stall, sudden intensive channel observed named as component broadband frequency, its corresponding mechanism explained vortex evolution between adjacent blades based dynamic mode decomposition technology. There three distinct frequency: (i) intermittent occurrence cell propagated current channel, (ii) wide range varying rate, (iii) considerable amplitude, e.g., reaching 21.1%–42.2% that addition, both amplitude gradually decreased increased 0.887QBEP. This study clarified internal behaviors if occurred, which important assess stability units.

Language: Английский

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Investigation on passive suppression method of hump characteristics in a large vertical volute centrifugal pump: Using combined diffuser vane structure

Energy, Journal Year: 2024, Volume and Issue: 304, P. 132067 - 132067

Published: June 17, 2024

Language: Английский

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Influence mechanism of impeller internal flow structure in the pump-mode hump instability of pump turbine: A compressible flow solution

Journal of Energy Storage, Journal Year: 2024, Volume and Issue: 92, P. 112049 - 112049

Published: May 22, 2024

Language: Английский

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Research on internal cavitation flow in axial flow pump focusing on the energy dissipation under varied operating conditions

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

Published: March 1, 2025

Cavitation poses a significant challenge to the performance of axial flow pumps, leading undesirable vibration and noise levels. Under off-design conditions, likelihood cavitation occurrence increases. This research delves into influence blade tip clearance on internal field within pump. Utilizing modified Shear stress transport k-ω turbulence model, numerical simulations are carried out across diverse operational scenarios varying numbers scrutinize characteristics energy dissipation distribution. The study reveals that decrease in number corresponds progression bubble formation inside impeller, spanning from trailing edge. Additionally, at comparable numbers, prevalence large rate bubbles becomes more pronounced. Throughout single impeller rotation cycle, vortex structure goes through cyclical process generation, breakdown, reemergence, with lower intensifying structure. Energy loss pump predominantly concentrated tip, hub, walls, diminishing losses toward hub as decreases. pressure propulsion power constitutes portion its distribution located edges impeller. evolution amplifies intensity extent thrust power.

Language: Английский

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Numerical investigation of no-load startup in a high-head Francis turbine: Insights into flow instabilities and energy dissipation

Physics of Fluids, Journal Year: 2024, Volume and Issue: 36(3)

Published: March 1, 2024

The presented paper numerically investigates the internal flow behaviors and energy dissipation during no-load startup process toward a Francis turbine. Passive runner rotation is implemented through angular momentum balance equation accompanied by dynamic mesh technology user defined function. Three phases of rotational speed are identified: stationary, rapid increase, slow increase. Head exhibits monotonic decrease, rise fall, eventual fluctuation. Flow rate shows quasi-linear pressure fluctuations in vaneless region primarily dominated frequencies induced Rotor-Stator Interaction broad frequency range below 50 Hz, 30 Hz draft tube. Runner inlet experiences positive to negative incidence angles, causing intense separation unstable structures. Draft tube large-scale recirculation evolving vortex Energy loss analysis based on entropy production method highlights as primary contributors. within an initial subsequent then again stationary increase phases. While phase Turbulent significantly contribute loss, with trends matching total production. Maximum locations correspond wall, emphasizing importance generation. This study establishes foundational insights into hydrodynamics modes hydraulic turbine startup, paving way for further research.

Language: Английский

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