Experimental investigation on the effect of axial gap on performance and unsteady pressure pulsations of low head axial flow hydraulic turbine

Ohiemi, Israel Enema; Sheng, Yang Sun; Singh, Punit; Li, Yanjun

doi:10.1016/j.flowmeasinst.2022.102255

Cited by 8 publications

(3 citation statements)

References 22 publications

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“…The results verified that unsteady flow field simulation was able to significantly improve the accuracy of flow simulation in the cone region, but no turbulence model could accurately predict the complex phenomena in the experiment. Ohiemi et al [23] measured dynamic pressure pulsation under different base gap and different flow conditions through pressure sensors installed in axial flow turbines, and the experimental results confirmed that the reduction in the base gap would increase the pressure pulsation.…”

Section: Introductionmentioning

confidence: 91%

Inner Flow Analysis of Kaplan Turbine under Off-Cam Conditions

Yan,

Luo,

Zhao

et al. 2024

Energies

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Kaplan turbines are widely utilized in low-head and large flow power stations. This paper employs Computational Fluid Dynamics (CFD) to complete numerical calculations of the full flow channel under different blade angles and various guide vane openings, based on 25 off-cam experimental working conditions. The internal flow characteristics of the runner blade and draft tube are analyzed, and a discriminant number for quantitatively assessing the flow uniformity of the draft tube is proposed. The results indicate that low-frequency and high-amplitude pressure pulsations occur on the high- and low-pressure edge of the blade when the opening is small, with pulsations decreasing as the opening increases. The inner flow line of the draft tube is disturbed when both the blade angle and opening are small. Additionally, the secondary frequency of the draft tube inlet is double that of the vane passing frequency. The discriminant number of the flow inhomogeneity approaches 0 under optimal flow conditions. The number increases continuously with the decrease in efficiency, and the flow in the three piers of draft tube becomes more nonuniform. The research results provide a reference for enhancing performance and ensuring the operational stability of Kaplan turbines.

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Section: Introductionmentioning

confidence: 91%

Inner Flow Analysis of Kaplan Turbine under Off-Cam Conditions

Yan,

Luo,

Zhao

et al. 2024

Energies

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“…9 The uneven distribution of clearance width will reduce the stability of flow field in the blade top area, cause the leakage flow at the blade top to show obvious unsteady characteristics, induce high amplitude pressure pulsation, lead to the increase of runner radial force, and even lead to the rubbing or seizure between the impeller and the housing in serious cases. 10,11 At present, the calculation of runner eccentricity is mainly achieved through direct measurement, and it is very difficult to monitor the changes in runner eccentricity in real time during the operation of hydraulic turbines. Because the eccentric operation of the runner inevitably leads to changes in the internal pressure pulsation of the hydraulic turbine, it is possible to predict the degree of eccentricity of the runner through changes in the pressure pulsation signal.…”

Section: Introductionmentioning

confidence: 99%

“…During the operation of the hydraulic turbine, due to factors such as runner wear, cavitation, and unit vibration, the runner will form a certain degree of eccentricity, resulting in uneven circumferential distribution of blade tip clearance 9 . The uneven distribution of clearance width will reduce the stability of flow field in the blade top area, cause the leakage flow at the blade top to show obvious unsteady characteristics, induce high amplitude pressure pulsation, lead to the increase of runner radial force, and even lead to the rubbing or seizure between the impeller and the housing in serious cases 10,11 . At present, the calculation of runner eccentricity is mainly achieved through direct measurement, and it is very difficult to monitor the changes in runner eccentricity in real time during the operation of hydraulic turbines.…”

Section: Introductionmentioning

confidence: 99%

Prediction of runner eccentricity and Alford force of a Kaplan turbine based on variational mode decomposition

Hu,

Liu,

Wang

et al. 2024

Energy Science & Engineering

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The rotor blades of an axial‐flow turbine are cantilever structures, and there is inevitably a gap between them and the casing. Due to factors such as rotor wear and unit vibration, the eccentricity of the impeller will change during the operation of the turbine, resulting in the impeller being affected by additional radial forces, which can even lead to rubbing or biting between the impeller and the casing. To monitor the eccentricity of the impeller and the additional radial forces in real time during the operation of the turbine, this study conducted numerical simulations of the internal flow of the turbine under different eccentricities of the impeller, and analyzed the characteristics of pressure pulsation and impeller radial force in the turbine using the variational mode decomposition method. The results showed that there was a good linear relationship between the eccentricity of the impeller and the amplitude of the frequency corresponding to the rotor in pressure pulsation at the monitoring point and the Alford force acting on the impeller. Based on this finding, we established mathematical formulas for the relationship between the pressure pulsation at the monitoring point and the eccentricity of the impeller, as well as the eccentricity of the impeller and the Alford force acting on it. According to these formulas, we only need to monitor the pressure pulsation during the operation of the turbine to realize the real‐time monitoring of the eccentricity of the impeller and the Alford force, which is of great significance for ensuring the safe and stable operation of the turbine.

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