scholarly journals Analysis of Flow Field Characteristics and Pressure Pulsation in Horizontal Axis Double-Runner Francis Turbine

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2671
Author(s):  
Chunxia Yang ◽  
Jiawei Wu ◽  
Dinge Xu ◽  
Yuan Zheng ◽  
Xueyuan Hu ◽  
...  
Keyword(s):  
Flow Field ◽  
Working Conditions ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Horizontal Axis ◽  
Francis Turbine ◽  
Back Surface ◽  
Average Efficiency ◽  
Flow Field Characteristics ◽  
The Relationship

Horizontal axis double-runner Francis turbines have great advantages in the development of small hydropower plants, but the arrangement of double runners aggravates the complexity of the water flow between runners, and the mutual influence of the two runners cannot be ignored. In order to explore the relationship between the performance and the internal flow field and investigate the pressure pulsation characteristics of the double-runner Francis turbine, the steady and unsteady numerical analysis of the full flow channel of a prototype turbine was carried out based on the Realizable k-epsilon model and the polyhedral mesh method. The results show that the relationship between the average efficiency of the two runners and the flow difference between the runners is negatively correlated. As the flow rate difference between the runners on both sides increases, the average efficiency of the runners decreases. The draft tube flow of a horizontal-axis turbine has a profound effect on the flow field characteristics in the runner. When the working conditions change, the turning and converging timing of the mainstream at the outlet of the two runners will change. The movement of the mainstream promotes the change in location of the dead water zone. The existence of the vortex zone makes the pressure distribution at the outlet of the runner uneven, which is an important reason for the asymmetry of the flow in the runner. The analysis of pressure pulsation and its frequency spectrum shows that when the working conditions change, the low-frequency, strong pressure pulsation area on the surface of the guide vane will regularly migrate between the two runners, while the high-frequency pressure pulsation that occurs in the bladeless zone will dissipate in the runner. The doubling of the blade frequency on the pressure surface and back surface of the blades gradually attenuates with the increase of frequency. The pressure pulsation attenuation on the surface of the high-position blade conforms to the linear law, and the attenuation of the pressure pulsation on the surface of the low-position blade conforms to the exponential law. The research in this paper provides a certain reference value for revealing the flow field mechanism and pressure pulsation characteristics of the double-runner Francis turbine.

scholarly journals Hydrodynamic Interactions between Bracket and Propeller of Podded Propulsor Based on Particle Image Velocimetry Test

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1142
Author(s):  
Dagang Zhao ◽  
Chunyu Guo ◽  
Tiecheng Wu ◽  
Wei Wang ◽  
Xunbin Yin
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Working Conditions ◽  
Cross Sections ◽  
Particle Image ◽  
Podded Propulsor ◽  
Image Velocimetry ◽  
Theoretical Significance ◽  
Practical Engineering ◽  
Flow Field Characteristics

In this study, particle image velocimetry was used to measure the fine flow-field characteristics of an L-type podded propulsor in various working conditions. The flow-field details at different cross-sections between the propeller and the inclined bracket were compared and analyzed, allowing for more intuitive comparison of the flow-field characteristics of L-type podded propulsors. The interference mechanisms among the propeller, pod, and bracket of the L-type podded propulsors at different advance coefficients, deflection angles, and deflection directions were investigated in depth. The results of this study can serve as reference material and provide technical support for the design and practical shipbuilding application of L-type podded propulsors. Therefore, the results have theoretical significance and practical engineering value.

Analysis of Off-Design Flow Field and Prediction of Performance in Hydraulic Turbine

2014 ◽  
Vol 496-500 ◽  
pp. 877-880
Author(s):  
Feng Xia Shi ◽  
Jun Hu Yang ◽  
Xiao Hui Wang
Keyword(s):  
Flow Field ◽  
Pressure Distribution ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Hydraulic Turbine ◽  
Design Flow ◽  
External Characteristic ◽  
Distribution Of Flow

Two models of hydraulic turbine based on pump in reversal were simulated. Pressure distribution of flow field in Variable conditions was analysed and external characteristic was forecasted for hydraulic turbine. It was shown: the head increased with flow increased, with increasing of flow rate, efficiency first increased and then decreased. Compared with the turbine with a guide vane, the head of two models was almost equal, but the disparity of efficiency was large, and the efficiency of hydraulic turbine with a guide vane above on the efficiency of hydraulic turbine without guide vane. Pressure pulsation was existent in runner inlet. From runner inlet to runner outlet, the pressure distributed evenly from high to low. Added with a guide vane, the pressure distribution was more evenly than before and the Amplitude of pressure fluctuation decreased.

scholarly journals Research on Unsteady Hydraulic Features of a Francis Turbine and a Novel Method for Identifying Pressure Pulsation Transmission Path

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1216 ◽  
Author(s):  
Shuo Wang ◽  
Liaojun Zhang ◽  
Guojiang Yin ◽  
Chaonian Guan
Keyword(s):  
Pressure Pulsation ◽  
Guide Vane ◽  
Fluid Pressure ◽  
Flow Channel ◽  
Transfer Entropy ◽  
Francis Turbine ◽  
Transmission Path ◽  
Hydropower House ◽  
Entire Flow ◽  
Novel Method

It is of significant value to understand the unsteady hydraulic features and pressure pulsation transmission path in the flow channel through a turbine for providing technical support for turbine design and optimization, as well as laying a foundation for analysis of the stability and the coupled vibration of the hydropower house. In this paper, a three-dimensional mechanics–hydraulics–concrete structure coupled numerical model was established to accurately simulate Francis hydraulic machinery, including the high-rotating turbine runner and fixed guide vane, the unsteady flowing water, the structure of the entire flow channel, as well as the dynamic interaction between them. Turbulent hydraulic features of flow condition and pressure pulsation in design operation were explored using the detached eddy simulation (DES) turbulence model. Then, a novel method was proposed to identify the fluid pressure pulsation transmission path based on the time-delayed transfer entropy method and wavelet theory. On basis of time and frequency analysis of pressure calculation results, investigation into identification of pressure pulsation transmission path was performed using the method of traditional transfer entropy and the method adopted in this paper. The pressure pulsation transmission features in the entire flow channel were revealed during operation of the large-scale Francis turbine. The research method and results could not only lay a basis for exploring the structural vibration regularity of the hydropower house but also provide a scientific reference for vibration reduction design of the hydropower house.

Computational fluid dynamics study on the drag and flow field differences between the single and coupled bends

2016 ◽  
Vol 38 (2) ◽  
pp. 163-175 ◽  
Author(s):  
Ran Gao ◽  
Shikuo Chen ◽  
Angui Li ◽  
Zhigang Yang ◽  
Beihua Cong
Keyword(s):  
Flow Field ◽  
Coupling Effect ◽  
Guide Vane ◽  
Reynolds Stress Model ◽  
Installation Space ◽  
Centerline Velocity ◽  
Practical Application ◽  
Coupling Conditions ◽  
Fluid Resistance ◽  
Flow Field Characteristics

Owing to the limited installation space and duct size, coupled fittings are common in the duct systems of buildings. The coupling effect leads to changes in drag and fan energy consumption. This study investigates duct drag and flow field characteristics under coupling conditions. Experiments and numerical simulations with the Reynolds stress model are conducted. Flow field changes, flow field deformation, and drag changes in the duct are analyzed. Regardless of the coupling form, the velocity near the inner arc is fast, whereas that near the outer arc is slow. Under three different coupling connection conditions (S-shaped, L-shaped, and U-shaped), the outlet velocity gradient of the U-shaped coupling connection is the least obvious. After the fluid flows through the bend, a significant centerline velocity reduction can be observed, even greater than that in the bend. The lowest centerline velocity lies within the range of 2.5 D to 4.5 D after the bend. Coupling connection has an insignificant effect on upstream duct resistance. The resistance of single bend is less than that of the downstream bend for the coupled bend and greater than that of the upstream bend under coupling conditions. Practical application: Coupling effect is common in practical application of ventilation engineering. This effect leads to the change of fluid resistance loss of ducts and pipes. However, few researchers focus on this effect. This study finds that regardless of the coupling form, the velocity near the inner arc is fast, whereas that near the outer arc is slow. It means the guide vane should be set near inner arc. L-shaped coupling connection has the largest downstream piping resistance. The resistance of the downstream piping under S-shaped coupling is the least, thus L-shaped coupling connection should be avoided as far as possible in practical application.

Numerical Analysis on the Internal Flow Field and Adsorption Performance of a Non-Contact Vortex Gripper

2013 ◽  
Vol 433-435 ◽  
pp. 1959-1964 ◽  
Author(s):  
Zhi Jian Zheng ◽  
Dong Tai Liang ◽  
Bo Lu ◽  
Jun Hui Huang
Keyword(s):  
Numerical Analysis ◽  
Flow Field ◽  
Working Conditions ◽  
Negative Pressure ◽  
Swirling Flow ◽  
Internal Flow ◽  
Pressure Center ◽  
Adsorption Performance ◽  
Maximum Value ◽  
Flow Field Characteristics

Based on the establishment of the geometry and equations of non-contact vortex gripper, the numerical analysis of the internal flow field characteristics and the key parameters affecting the adsorption performance was carried out. The results showed that: for the single air-entrance gripper, the negative pressure center not coincides at the geometric center of the gripper. Besides, with the movement of swirling flow, the position of the negative pressure center transformed; When the geometric parameters and working conditions are fixed, there is the most suitable air gap making the maximum value of negative pressure and adsorption force; Compared to single air-entrance gripper, double air-entrance gripper have better adsorption stability.

scholarly journals Analysis of Timing Effect on Flow Field and Pulsation in Vertical Axial Flow Pump

2021 ◽  
Vol 9 (12) ◽  
pp. 1429
Author(s):  
Fan Yang ◽  
Pengcheng Chang ◽  
Yao Yuan ◽  
Na Li ◽  
Rongsheng Xie ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Flow Condition ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Low Frequency ◽  
Axial Flow ◽  
Outlet Flow ◽  
Axial Flow Pump ◽  
Flow Pump

Vertical axial flow pump device has the characteristics of large flow and low head, which is widely used in pumping station projects with head of 3–9 m. In order to study the influence of the timing effect of the impeller relative flow channel and guide vane on the flow field and pulsation in the axial flow pump device, the whole flow channel of the vertical axial flow pump device was taken as the research object. The reliability of the numerical simulation was verified by physical model test. The flow field characteristics and pressure pulsation characteristics of the inlet and outlet regions of the impeller, the guide vane and the campaniform inlet conduit at different timing positions of the impeller under different flow rates were analyzed. The results show that the pressure coefficient distribution of the impeller inlet of the vertical axial flow pump device presents four high-pressure areas and four low-pressure areas with the rotation of the impeller. The pressure pulsation at the inlet and outlet of the impeller is mainly affected by the rotation of the impeller, and the main frequency is 4 times the rotation frequency amplitude of pressure pulsation decreases with the increase of flow rate. When the flow rate increased from 0.8 Qbep to 1.2 Qbep, the average velocity circulation at the guide vane outlet decreased by 12%; there is an obvious negative value region of the internal regularized helicity of the guide vane. When the flow rate increases from 0.8 Qbep to 1.2 Qbep, the amplitude of the pressure pulsation coefficient at the outlet of the guide vane decreases gradually, with a decrease of 94%. When the flow rate is 1.2 Qbep, the main frequency and the secondary frequency of the pressure pulsation are both low-frequency, with obvious low-frequency pulsation characteristics. Under the small flow condition of 0.8 Qbep, the outlet flow fluctuation of seven guide vane was 18.9% on average, and the flow variation of each guide vane was large. Under the optimal flow condition of 1.0 Qbep and large flow condition of 1.2 Qbep, the outlet flow fluctuation of 7 guide vane is 4.7% and 0.56% on average, and the flow change of each guide vane is stable. The outlet flow of the guide vane is mainly concentrated in two guide vane slots of the guide vane, and the flow ratios are 30.56%, 30.14% and 29.16% under three flow conditions, respectively. The research results provide a scientific basis for the optimization design and stable operation of vertical axial flow pump device.

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