Analysis of the Energy Loss Mechanism of Pump-Turbines with Splitter Blades under Different Characteristic Heads

Gui, Zhonghua; Xu, Zhe; Li, Dongkuo; Zhang, Fei; Zhao, Yifeng; Xu, Lianchen; Zheng, Yuan; Kan, Kan

doi:10.3390/w15152776

Cited by 3 publications

(2 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The convergence criterion was set to 10 −5 . The residual value reached 10 −5 ; it was considered as convergence [28,29].…”

Section: Boundary Conditions and Calculation Methodsmentioning

confidence: 99%

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

Xu,

Cheng,

Lin

et al. 2023

Water

View full text Add to dashboard Cite

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.

show abstract

“…The convergence criterion was set to 10 −5 . The residual value reached 10 −5 ; it was considered as convergence [28,29].…”

Section: Boundary Conditions and Calculation Methodsmentioning

confidence: 99%

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

Xu,

Cheng,

Lin

et al. 2023

Water

View full text Add to dashboard Cite

show abstract

“…Finally, they used the entropy generation theory to analyze the source of the loss, and pointed out that the hydraulic loss in the flow channel was mainly affected by the velocity gradient, not by the vortex structure. Many scholars [25][26][27] have studied the S-characteristic region through numerical calculations or PIV tests, obtained the flow and pressure-pulsation conditions at different working points, analyzed the positions of and reasons for vortex generation, and found that the flow under pump-braking conditions was the most unstable.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Flow Behavior and Pressure Fluctuation of a Pump Turbine with Splitter Blades in Part-Load Pump Mode

Xiao,

Ren,

Chen

et al. 2024

Energies

View full text Add to dashboard Cite

The internal flow of a pump turbine is unstable in part-load pump mode for small guide-vane openings, and the strong vibration caused by pressure pulsation is related to the safe and stable operation of the unit. A pump turbine with a six-splitter-blade runner was chosen for unsteady simulation analyses. A standard k-epsilon turbulence model was adopted to study the unsteady flow and pressure pulsation in part-load pump mode. The predicted results show that the flow in the draft tube and the runner with splitter blades was relatively stable and the flow of the blade-to-blade channel was symmetrical. When the inlet and outlet velocity distribution of the vanes was not uniform, a vortex began to form in the stay-vane domain. The reason for this vortex formation is explained, and it is pointed out that the existence of the vortex and backflow leads to uneven velocity distribution. The unsteady calculation results showed that the pressure-pulsation peak-to-peak amplitudes in the vaneless area and guide vanes were much higher than those of other monitor points because of rotor–stator interference between the rotating runner and the vanes. In addition, the pulsation characteristics of the monitor points at different circumferential positions in the vaneless region were quite different. In the vaneless area, the velocity gradient along the circumferential direction was very large, and there was a phenomenon of backflow. Also, the pressure pulsation was 0.2 times that of the runner rotational frequency, and the blade-passing frequency was a third-order frequency. At the outlet of the guide vane, the pressure pulsation was mainly of a low frequency with a complex vortex flow. Finally, the pressure pulsation began to decrease rapidly in the stay-vane region.

show abstract