Discussion on Stochastic Analysis of Hydraulic Vibration in Pressurized Water Diversion and Hydropower Systems

Zhou, Jianxu; Chen, Yu

doi:10.3390/w10040353

Cited by 10 publications

(8 citation statements)

References 29 publications

(40 reference statements)

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“…However, sometimes the frequencies of external disturbances are similar or equal to the natural frequencies of the pressurized pipeline system, hydraulic resonance and a self-excited vibration could happen because of the system's inherent instabilities. 6 With the rapid development of hydropower stations with longer pipelines, larger unit capacity, lower runner rotational speed, and more frequent switching of operating conditions, the forced vibration even the severe hydraulic resonance could be easily generated and finally influence the structure safety and operation stability of hydropower systems. [7][8][9] Numerous existing research have been carried out on the pressure fluctuations in hydropower systems, including experimental tests and numerical simulations.…”

Section: Introductionmentioning

confidence: 99%

Effect of turbine's torque and speed variation on hydraulic vibration analysis during transient processes

Shen,

Cui,

Zhou

et al. 2024

Energy Science & Engineering

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With the rapid development of large‐capacity hydraulic turbines and pumped‐storage power stations, hydraulic vibration analysis attracts increasing attention nowadays. To explore the influence of torque and speed variation on hydraulic vibration characteristics during transient processes and ensure the stability of hydropower stations, an improved analytical formula of turbine impedance involving the torque and speed variation was then derived. The free vibration analysis and forced vibration analysis using the transfer matrix method and the hydraulic impedance method were carried out. According to the numerical simulations, the obtained attenuation factors show differences in magnitude which illustrates that the torque variation and speed variation in transients do affect the damping rate of the vibration. In addition, the results indicated the natural angular frequencies of hydropower system were mainly dependent on the length of water conveyance system and pipe characteristics. It can be inferred form vibration mode shapes that for some specific frequencies, the magnitude of oscillatory pressure head and flow rate along the downstream tail tunnel are influenced by the hydraulic turbine. The correlation between the turbine impedance and guide vane openings tells that the hydraulic impedance is getting smaller as the opening increases. What's more, the corresponding free vibration analysis shows that the absolute value of the damping rate is closely related to the value of the flow rate.

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Section: Introductionmentioning

confidence: 99%

Effect of turbine's torque and speed variation on hydraulic vibration analysis during transient processes

Shen,

Cui,

Zhou

et al. 2024

Energy Science & Engineering

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“…Hydraulic vibration is a periodic hydraulic transient that exists in various water conveyance systems and may result in instabilities and local destructions [29,30]. With complex condition switches under frequency regulation tasks, both the initial and boundary conditions become extremely complicated, especially for off-design conditions.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Vibration and Possible Exciting Sources Analysis in a Hydropower System

et al. 2021

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To understand the hydraulic vibration characteristics in a traditional hydropower system and identify possible exciting sources that may induce serious hydraulic vibrations in the flow passage, experimental tests and numerical calculations were conducted for different operating conditions. The experimental results show that the pressure fluctuations are mainly related to the vortex rope phenomena in the draft tube, and the dominant frequency of pressure fluctuation is 0.2~0.4 times the runner rotational frequency (fn). The numerical results show all the attenuating factors are negative, which indicates the system itself is stable on the condition that all the hydraulic elements have steady operating performance. The free vibration analyses confirm that the frequency range of the vortex rope in the draft tube partly overlaps the natural frequencies of the hydropower system. Apart from the vortex rope, the runner rotational frequency is another common frequency that is approximately equal to the frequency of the 10th vibration mode. From the vibration mode shapes, it is inferred that a small disturbance in its frequency close or equal to a specific natural frequency of the vibration mode could induce large pressure oscillations in the tail tunnel. In light of the system’s response to different forcing frequencies, the vortex rope formed under off-design conditions and runner rotational frequency is verified to be the potential exciting source of a traditional hydropower system, and the frequency 0.2 fn is much more dangerous than other disturbances to the system.

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“…First, frequent changes in unit working conditions can lead to highly complex fluid flow in the pressure diversion pipeline, resulting in unstable unit operation and abnormal shutdown Zhang et al (2017aZhang et al ( , 2017b. Second, pressure fluctuations in the draft tube, the water hammer phenomenon in the passing water system, and unit vibration caused by misalignment of the generator's rotor axis also affect stable unit operation (An et al, 2017;Fu et al, 2019;Zhou and Chen, 2018). Third, as hydropower stations continue to be used over time, the age of equipment is climbing and thus poses notable challenges to stable station operations.…”

Section: Introductionmentioning

confidence: 99%

Mittag–Leffler stability and finite-time control for a fractional-order hydraulic turbine governing system with mechanical time delay: An linear matrix inequalitie approach

Chen

Wang

Tian

et al. 2021

Journal of Vibration and Control

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This article mainly studies the Mittag–Leffler stability and finite-time control of a time-delay fractional-order hydraulic turbine governing system. First, properties of the Riemann–Liouville derivative and some important lemmas are introduced. Second, considering the mechanical time delay of the main servomotor, the mathematical model of a fractional-order hydraulic turbine governing system with mechanical time delay is presented. Then, based on Mittag–Leffler stability theorem, a suitable sliding surface and finite-time controller are designed for the hydraulic turbine governing system. The system stability is confirmed, and the stability condition is given in the form of linear matrix inequalities. Finally, the traditional proportional–integral–derivative control method and an existing sliding mode control method are selected to verify the effectiveness and robustness of the proposed method. This study also provides a new approach for the stability analysis of the time-delay fractional-order hydraulic turbine governing system.

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Discussion on Stochastic Analysis of Hydraulic Vibration in Pressurized Water Diversion and Hydropower Systems

Cited by 10 publications

References 29 publications

Effect of turbine's torque and speed variation on hydraulic vibration analysis during transient processes

Effect of turbine's torque and speed variation on hydraulic vibration analysis during transient processes

Hydraulic Vibration and Possible Exciting Sources Analysis in a Hydropower System

Mittag–Leffler stability and finite-time control for a fractional-order hydraulic turbine governing system with mechanical time delay: An linear matrix inequalitie approach

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