Numerical analysis of unsteady tip leakage vortex cavitation cloud and unstable suction-side-perpendicular cavitating vortices in an axial flow pump

2015 ◽  
Vol 77 ◽  
pp. 244-259 ◽  
Author(s):  
Desheng Zhang ◽  
Lei Shi ◽  
Weidong Shi ◽  
Ruijie Zhao ◽  
Haiyu Wang ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Axial Flow ◽  
Suction Side ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

Experiments of Tip Leakage Vortex Cavitation Cloud and Suction-Side-Perpendicular Cavitating Vortices in an Axial Flow Pump

2018 ◽  
Author(s):  
Xi Shen ◽  
Desheng Zhang
Keyword(s):  
Pressure Pulsation ◽  
Axial Flow ◽  
Suction Side ◽  
High Speed Photography ◽  
Suction Surface ◽  
Rate Condition ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

The tip leakage vortex (TLV) cavitation mechanism of axial flow pump was investigated with the results of high speed photography and pressure pulsation measurement. The tip leakage vortex cavitation morphology and the transient characteristics of the TLV-induced suction-side-perpendicular cavitating vortices (SSPCV) were analyzed under different flow rates and different cavitation numbers which were combined with the time domain spectrum of pressure fluctuation to elucidate the relationship between the tip cavitation and pressure pulsation. The results showed that cavitation inception occurs earlier with more unstable tip leakage vortex cavitation shape under part-load flow rate condition, and the cavitation is more intense with the decrease of the cavitation number. The inception of SSPCV is attributed to the tail of the shedding cavitation cloud originally attached on the suction side (SS) surface of blade, moving toward the adjacent blade perpendicular to the suction surface, resulting in a flow blockage. With further decrease of pressure, the SSPCVs grow in size and strength, accompanied with a rapid degradation in performance of the pump. The cavitation images and the corresponding circumferential pressure distribution with the same phase showed that the lowest pressure coincides with the suction surface (SS) corner, The pressure was found to decrease along with the occurrence of the cavitation structure.

Numerical and Experimental Investigation of Tip Leakage Vortex Trajectory in an Axial Flow Pump

2013 ◽  
Author(s):  
Desheng Zhang ◽  
Weidong Shi ◽  
Suqing Wu ◽  
Dazhi Pan ◽  
Peipei Shao ◽  
...  
Keyword(s):  
Flow Rate ◽  
Axial Flow ◽  
Tip Clearance ◽  
High Speed Photography ◽  
Rate Condition ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Starting Point ◽  
Axial Flow Pump ◽  
Flow Pump

In this paper, the tip leakage vortex (TLV) structures in an axial flow pump were investigated by numerical and experimental methods. Based on the comparisons of different blade tip clearance size (i.e., 0.5 mm, 1mm and 1.5mm) and different flow rate conditions, TLV trajectories were obtained by Swirling Strength method, and simulated by modified SST k-ω turbulence model with refined high-quality structured grids. A high-speed photography test was carried out to capture the tip leakage vortex cavitation in an axial flow pump with transparent casing. Numerical results were compared with the experimental leakage vortex trajectories, and a good agreement is presented. The detailed trajectories show that the start point of tip leakage vortex appears near the leading edge at small flow rate, and it moves from trailing edge to about 30% chord span at rated flow rate. At the larger flow rate condition, the starting point of TLV shifts to the middle of chord, and the direction of TLV moves parallel to the blade hydrofoil. As the increasing of the tip size, the start point of TLV trajectories moves to the central of chord and the minimum pressure in vortex core is gradually reduced.

A study on tip leakage vortex dynamics and cavitation in axial-flow pump

2017 ◽  
Vol 49 (3) ◽  
pp. 035504 ◽  
Author(s):  
Lei Shi ◽  
Desheng Zhang ◽  
Yongxin Jin ◽  
Weidong Shi ◽  
B P M (Bart) van Esch
Keyword(s):  
Vortex Dynamics ◽  
Axial Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

Numerical and experimental investigation of tip leakage vortex trajectory and dynamics in an axial flow pump

2015 ◽  
Vol 112 ◽  
pp. 61-71 ◽  
Author(s):  
Desheng Zhang ◽  
Weidong Shi ◽  
B.P.M. (Bart) van Esch ◽  
Lei Shi ◽  
Michel Dubuisson
Keyword(s):  
Experimental Investigation ◽  
Axial Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

Numerical simulation on hydraulic performance and tip leakage vortex of a slanted axial-flow pump with different blade angles

2021 ◽  
pp. 095440622110329
Author(s):  
Zhaodan Fei ◽  
Hui Xu ◽  
Rui Zhang ◽  
Yuan Zheng ◽  
Tong Mu ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Strain Tensor ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Tip Leakage Flow ◽  
Blade Angle ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

The blade angle has a great effect on hydraulic performance and internal flow field for axial-flow pumps. This research investigated the effect of the blade angle on hydraulic performance and tip leakage vortex (TLV) of a slanted axial-flow pump. The hydraulic performance and the TLV are compared with different setting angles. The dimensionless turbulence kinetic energy (TKE) is used to investigate the TLV. A novel variable fv is utilized to analyze the relation among the TLV, strain tensor and vorticity tensor. The proper orthogonal decomposition (POD) method is used to analyze TLV structure. The results show that with the increase of the blade angle, the pump head is getting larger, the flow rate of the best efficiency moves to be larger, and both the primary TLV (P-TLV) and the secondary TLV (S-TLV) are getting stronger. The P-TLV often exists in the outer edge of TKE distribution and S-TLVs often exist in the largest value area of TKE. This phenomenon is more evident with blade angle increasing. Through POD method, it shows that the first six modes contain more than 90% of TKE. The reason why the TKE value near the region of S-TLV is high is that the tip leakage flow is a kind of jet-like flow with high kinetic energy. The main structure of the P-TLV is shown in modes 4−6, resulting in a reflux zone but not with the highest TKE.

Study on unsteady tip leakage vortex cavitation in an axial-flow pump using an improved filter-based model

2017 ◽  
Vol 31 (2) ◽  
pp. 659-667 ◽  
Author(s):  
Desheng Zhang ◽  
Lei Shi ◽  
Ruijie Zhao ◽  
Weidong Shi ◽  
Qiang Pan ◽  
...  
Keyword(s):  
Axial Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

scholarly journals Numerical Analysis of the Effect of Cavitation on the Tip Leakage Vortex in an Axial-Flow Pump

2021 ◽  
Vol 9 (7) ◽  
pp. 775
Author(s):  
Hu Zhang ◽  
Jun Wang ◽  
Desheng Zhang ◽  
Weidong Shi ◽  
Jianbo Zang
Keyword(s):  
Axial Flow ◽  
Strength Distribution ◽  
Cavitating Flows ◽  
Suction Surface ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Clearance Flow ◽  
Axial Flow Pump ◽  
Vorticity Transport ◽  
Flow Pump

To understand the effect of cavitation on the tip leakage vortex (TLV), turbulent cavitating flows were numerically investigated using the shear-stress transport (SST) k–ω turbulence model and the Zwart–Gerber–Belamri cavitation model. In this work, two computations were performed—one without cavitation and the other with cavitation—by changing the inlet pressure of the pump. The results showed that cavitation had little effect on the pressure difference between the blade surfaces for a certain cavitation number. Instead, it changed the clearance flow and TLV vortex structure. Cavitation caused the TLV core trajectory to be farther from the suction surface and closer to the endwall upstream of the blade. Cavitation also changed the vortex strength distribution, making the vortex more dispersed. The vortex flow velocity and turbulent kinetic energy were lower, and the pressure pulsation was more intense in the cavitating case. The vorticity transport equation was used to further analyze the influence of cavitation on the evolution of vortices. Cavitation could change the vortex stretching term and delay the vortex bending term. In addition, the vortex dilation term was drastically changed at the vapor–liquid interface.

Experimental and numerical investigation of tip leakage vortex cavitation in an axial flow pump under design and off-design conditions

2020 ◽  
pp. 095765092090629
Author(s):  
Xi Shen ◽  
Desheng Zhang ◽  
Bin Xu ◽  
Changliang Ye ◽  
Weidong Shi
Keyword(s):  
Shear Stress ◽  
Turbulence Model ◽  
Axial Velocity ◽  
Axial Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Sheet Cavitation ◽  
Shear Stress Transport ◽  
Axial Flow Pump ◽  
Flow Pump

The interaction of tip leakage flow and main flow in an axial flow pump can induce the tip leakage vortex, which causes the unstable flow and complex cavitation structures. In the present research, the modified shear stress transport k–ω turbulence model was utilized to predict the cavitating flow of the model pump under design and off-design conditions. Validations were carried out using high-speed photography techniques. Results show that the simulation results about cavitation performance based on the modified shear stress transport k–ω turbulence model agree well with the experimental results. Cavitation inception occurs more possible at part-load conditions, and with the increase of the flow rate, the starting point of tip leakage vortex gradually moves to the back edge of the blade chord. Both the sheet cavitation and the triangular cavitation cloud that formed in the blade tip grow in size and intensity gradually with the decrease of cavitation number. Distributions of the cavity area fraction and axial velocity show that the tip leakage vortex cavitation locates at the radial coefficient r* = 0.95–1.0 with peaks at about r* = 0.97, while the sheet cavitation is found at r* = 0.5–0.9 on the suction side (SS). The cavitation structures lead to a significant decrease in the axial velocity, especially in the tip region of the blade.

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