Analysis of Channel Vortex and Cavitation Performance of the Francis Turbine under Partial Flow Conditions

Tao, Guo; Zhang, Jinming; Luo, Zhumei

doi:10.3390/pr9081385

Cited by 6 publications

(4 citation statements)

References 34 publications

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“…In this study, numerical simulations of threedimensional incompressible fluids have been carried out using the Reynolds time-averaged method, under which the continuity, momentum and total energy equations are given in equations ( 3)- (5). These three equations are the core of the numerical simulation method.…”

Section: Governing Equationsmentioning

confidence: 99%

“…Due to the fluid characteristics of water, it is extremely difficult to mechanically realize its control. 5 Francis turbine adopts a spiral case and stay vane to collect water flow, and uses guide vane to regulate the flow rate and flow. 6,7 This makes the runner very good for energy conversion, and the draft tube downstream of the runner plays a good role in energy recovery.…”

Section: Introductionmentioning

confidence: 99%

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Influence of runner blade number on hydraulic performance and flow control in draft tube of Francis turbine

Lu,

Su,

Tao

2024

Advances in Mechanical Engineering

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As a widely used core component of hydropower generation, the stable and safe operation of the Francis turbine plays a very important role in engineering applications. Therefore, the effects of different rotor blade numbers on the hydraulic performance and flow control of the draft tube of the Francis turbine are of great research value. This paper focuses on the rotor blade number 13, 14, 15, 16, and 17 in the prohibited and stabilized operating zones, each of which is taken as a working condition point. (Condition αref - HM and Condition 2 αref - HM). Computational Fluid Dynamics (CFD) numerical simulations were performed and analyzed. In terms of hydraulic performance, the increase in the number of blades increases the efficiency and power of the turbine under Condition αref - HM by 2.26% and 0.0021 MW respectively. The efficiency and power of the turbine under Condition αref - HM is also elevated, with the efficiency reaching a maximum of 91.77% at blade number 15, and the power of the same turbine reaching a maximum of 0.182 MW at runner blade number 13. From the 3D flow analysis of the turbine, the increase in the number of blades does not significantly change the flow state of the turbine’s draft tube. By defining the turbulence energy E, the fast Fourier transform of the turbulence energy signals on the two monitoring surfaces of the draft tube is used to obtain its main frequency, and the amplitude and phase at the typical main frequency are visualized, through which we can analyze the vortex band motion state on the two monitoring surfaces of the draft tube, and speculate the change of pressure pulsation of the draft tube. Such an analysis method has a guiding significance for us to improve the performance and stability of the turbine, which can be achieved by increasing or decreasing the number of blades.

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Section: Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of runner blade number on hydraulic performance and flow control in draft tube of Francis turbine

Lu,

Su,

Tao

2024

Advances in Mechanical Engineering

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“…Then, at the vicinity of the stator blades, and especially the runner, pressure drops rapidly, much faster than the pressure rise. Gauge pressure can drop even below zero (vacuum), near the suction side of the blades [47,48], or the spiraling vortex tube, also known as vortex rope in the relevant literature, emanating from the turbine hub [40,49]; indeed, the latter is well known to induce strong low-frequency vibrations to the whole turbine, which potentially threaten the integrity of the whole installation [50][51][52][53]. In any case, as the trajectory of a passing fish reaches the tailrace, pressure recovers gradually to near atmospheric conditions.…”

Section: Pressure Changesmentioning

confidence: 99%

State of the Art in Designing Fish-Friendly Turbines: Concepts and Performance Indicators

Koukouvinis

Anagnostopoulos

2023

Energies

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The expanding role of renewable energy sources in the electricity market share implies the increasing role of hydropower and the exploitation of unharnessed hydraulic potential, in the scope of sustainability and net zero emissions. Hydro-turbine design practices are expected to expand beyond achieving high efficiency goals, to multi-objective criteria ranging from efficient reversible operation to fish-friendly concepts. The present review paper outlines fundamental characteristics of hydropower, summarizing its potential impact toward aquatic life. Estimates of lethality for each damage mechanism are discussed, such as barotrauma, blunt impact and shearing, along with relevant advances in experimental techniques. Furthermore, numerical techniques are discussed, ranging from simple particle tracking to fully coupled six-degree-of-freedom tracking, which can be used to investigate candidate designs and their fish-friendly performance, presenting their advantages and disadvantages. Subsequently, a link to the individual damage mechanisms is established, to proposed holistic performance metrics, useful for providing estimates of fish-friendliness of a given hydropower installation. Finally, recent developments and design practices for fish-friendly turbine concepts are presented.

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“…When a hydraulic turbine is in nonoptimal working conditions, vibration is inevitable. Guo et al [21] found that as the opening of the guide vanes decreased, the cavitation phenomenon in the runner increased, and local high-pressure or negative pressure areas appeared on the blades. Zhou [22] concluded that the increase in the guide vane opening helped to reduce the pressure acting on the runner blades, and the backflow was more likely to occur at the end of the runner blades.…”

Section: Introductionmentioning

confidence: 99%

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

Xu,

Cheng,

Lin

et al. 2023

Water

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The research object was a Francis turbine, and the working conditions at 100%, 75%, 50%, 25%, and 1% opening were determined by the opening size of the guide vane. Large-Eddy Simulation (LES) was adopted as a turbulence model method to conduct three-dimensional unsteady turbulent numerical simulation of the entire flow channel of a Francis turbine, and the flow situation of various parts of the turbine under different working conditions was obtained. The flow characteristics of each component under different working conditions were analyzed, and the hydraulic performance of each part was evaluated. The factors that affected the stability of hydraulic turbines were identified, and their formation mechanisms and evolution laws were explored. The results show that the guide vane placement angle was reasonable in the guide vane area, and the hydraulic performance was fine. The impact on the stability of the hydraulic turbine was small. Further research showed that the hydraulic performance was poor in the runner area, and there were flow separation and detachment phenomena in the flow field. This created a channel vortex in the runner blade channel. The channel vortex promoted the lateral flow of water and had a significant impact on the stability of the hydraulic turbine. The diffusion section of the draft tube can dissipate most of the kinetic energy of the water flow in the draft tube area, and it had a good energy dissipation effect. However, the was a large pressure difference between the upper and lower regions of the diffusion section, and it generated a backflow phenomenon. It created vortex structures in the draft tube, and the stability of the hydraulic turbine was greatly affected.

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Analysis of Channel Vortex and Cavitation Performance of the Francis Turbine under Partial Flow Conditions

Cited by 6 publications

References 34 publications

Influence of runner blade number on hydraulic performance and flow control in draft tube of Francis turbine

Influence of runner blade number on hydraulic performance and flow control in draft tube of Francis turbine

State of the Art in Designing Fish-Friendly Turbines: Concepts and Performance Indicators

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

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