Unsteady pressure measurements on the runner of a Kaplan turbine during load acceptance and load rejection

Amiri, Kaveh; Mulu, Berhanu; Raisee, Mehrdad; Cervantes, Michel

doi:10.1080/00221686.2015.1110626

Cited by 54 publications

(52 citation statements)

References 10 publications

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“…The transition between the two operating points happens without occurrence of any special phenomenon; i.e., there is not any frequency appearing or mitigating during the load variation. The acquired results during the load variation from the high load to the BEP were similar; see Amiri et al, [15]. …”

Section: 1mentioning

confidence: 53%

“…5 due to the small time difference). After the RVR formation, frequency of the plunging mode increases with the guide vanes closure; see Amiri et al, [15]. The RVR amplitude in both the rotating and plunging modes increases as well.…”

Section: 2mentioning

confidence: 98%

“…Window size of 2.05 s with a 96% overlap was selected after sensitivity analysis. For detailed data analysis procedure refer to [14,15]. Experimental investigation of the model performed by Amiri et al [13] showed that RVR formation in the draft tube cone of the water turbine results in pressure oscillations with rotating and plunging modes.…”

Section: Discussionmentioning

confidence: 99%

“…Whereas, the rotating mode results in oscillation of the pressures with f RVR,st but with 180º phase difference. The pressure signals acquired at the draft tube cone were filtered with a narrow band pass filter around f RVR,st to isolate the effect of the RVR and then subtracted from the average of the signals as proposed by Amiri et al [15]. The resulting signals can be written as the superposition of the plunging and rotating modes:…”

Section: Discussionmentioning

confidence: 99%

“…The turbine was investigated during load variations between the three operating points. Similar operating conditions were selected by Amiri et al [15] to investigate transitions from one operating point to the other, but with different load variation scenarios.…”

Section: 1mentioning

confidence: 99%

See 4 more Smart Citations

Effects of load variation on a Kaplan turbine runner

Amiri¹,

Mulu

Cervantes

et al. 2016

International Journal of Fluid Machinery and Systems

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Introduction of intermittent electricity production systems like wind and solar power to electricity market together with the deregulation of electricity markets resulted in numerous start/stops, load variations and off-design operation of water turbines. Hydraulic turbines suffer from the varying loads exerted on their stationary and rotating parts during load variations since they are not designed for such operating conditions. Investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of a rotating vortex rope (RVR) in the draft tube. The RVR induces pressure pulsations in the axial and rotating directions called plunging and rotating modes, respectively. This results in oscillating forces with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. This study investigates the effect of transient operations on the pressure fluctuations exerted on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors for this purpose. The model was run in off-cam mode during different load variations. The results showed that the transients between the best efficiency point and the high load occurs in a smooth way. However, during transitions to the part load a RVR forms in the draft tube which induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode. Formation of the RVR during the load rejections coincides with sudden pressure change on the runner while its mitigation occurs in a smooth way.

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Section: 1mentioning

confidence: 53%

Section: 2mentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: 1mentioning

confidence: 99%

See 3 more Smart Citations

Effects of load variation on a Kaplan turbine runner

Amiri¹,

Mulu

Cervantes

et al. 2016

International Journal of Fluid Machinery and Systems

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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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Analysis of transient flow in a pump-turbine during the load rejection process

Wang

et al. 2018

J Mech Sci Technol

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Unsteady pressure measurements on the runner of a Kaplan turbine during load acceptance and load rejection

Cited by 54 publications

References 10 publications

Effects of load variation on a Kaplan turbine runner

Effects of load variation on a Kaplan turbine runner

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

Analysis of transient flow in a pump-turbine during the load rejection process

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