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.

Numerical investigation of tip flow dynamics and main flow characteristics with varying tip clearance widths for an axial-flow pump

2018 ◽  
Vol 233 (4) ◽  
pp. 476-488 ◽  
Author(s):  
Simin Shen ◽  
Zhongdong Qian ◽  
Bin Ji ◽  
Ramesh K Agarwal
Keyword(s):  
Flow Rate ◽  
Axial Flow ◽  
Tip Clearance ◽  
Main Stream ◽  
Specific Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Tip Separation Vortex ◽  
Flow Pump

The effects of varying tip clearance widths on tip flows dynamics and main flows characteristics for an axial-flow pump are studied employing computational fluid dynamics method. An analysis is presented for the distributions of turbulent kinetic energy, mean axial velocity, and mean vorticity magnitude at the specific flow rate of 0.7 Q BEP , focusing on flow patterns in the tip region with different tip clearance widths and associated flows. From the simulation results we find that the flow structure of tip vortex and its transportation strongly depend on the tip clearance width, especially for the extension of tip leakage vortex, appearance of induced vortex and the area of tip separation vortex. For a small clearance of 0.15 mm at 0.7 Q BEP, there is no tip separation vortex at the tip. When tip clearance width becomes larger, a tip separation vortex attaches more on the surface of blade tip as well as vortex intensity of tip flows increases. For tip clearances of 0.9 and 1.2 mm, there is a small part of induced vortex near the blade leading edge. Meanwhile, no induced vortex can be captured for tip clearances of 0.15 and 0.45 mm. The relative angle between the blade chord and tip leakage vortex trajectory reduces gradually when tip clearance width increases from 0.45 to 1.2 mm. Additionally, the radial position of tip leakage vortex core moves inwards as tip clearance width increases. Furthermore, a larger tip clearance width has greater effects on the main-stream characteristics especially near the shroud, which is due to more energy being exchanged between tip flows and main flows. At the flow rate 0.7 Q BEP, both the efficiency and head of the pump reduce with an increasing tip clearance because of greater energy loss.

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.

scholarly journals Study on tip leakage vortex in an axial flow pump based on modified shear stress transport k-ω turbulence model

2013 ◽  
Vol 17 (5) ◽  
pp. 1551-1555 ◽  
Author(s):  
Desheng Zhang ◽  
Dazhi Pan ◽  
Weidong Shi ◽  
Suqing Wu ◽  
Peipei Shao
Keyword(s):  
Shear Stress ◽  
Turbulence Model ◽  
Flow Rate ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Starting Point ◽  
Axial Flow Pump ◽  
Flow Pump

The tip leakage vortex structure and trajectory in an axial flow pump were investigated numerically and experimentally based on the modified shear stress transport k-? turbulence model. Numerical results were compared with the experimental leakage vortex trajectories, and a good agreement was presented. The detailed trajectories of tip leakage vortex show that the starting point of tip leakage vortex occurs near the leading edge at small flow rate, and it moves from leading edge to about 30% chord length at design flow rate. At larger flow rate condition, the starting point of tip leakage vortex shifts to the middle of chord.

Experimental Investigation of the Transient Patterns and Pressure Evolution of Tip Leakage Vortex and Induced-Vortices Cavitation in an Axial Flow Pump

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Shen Xi ◽  
Zhang Desheng ◽  
Xu Bin ◽  
Jin Yongxin ◽  
Shi Weidong ◽  
...  
Keyword(s):  
High Speed ◽  
Axial Flow ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Transient Pressure ◽  
Suction Surface ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

Abstract Cavitating flow is extremely complex in axial and mixed flow pumps, resulting in several adverse effects on pump performance. In this paper, the tip leakage vortex (TLV) cavitation patterns in an axial flow pump model were studied based on high-speed photography and transient pressure measurements. The TLV cavitation morphology and transient development of the induced suction-side-perpendicular cavitating vortices (SSPCVs) were investigated at multi-operating conditions. The time-domain of the transient pressure was employed to clarify the relationship between the tip cavitation and the pressure field. The results showed that cavitation inception occurred earlier with an unstable TLV cavitation shape at part-load conditions. Cavitation was more intense with a decrease of the cavitation number, presenting a larger area of triangular cavitation with the shedding of SSPCV. The inception of SSPCV was attributed to the tail of the shedding cavitation cloud originally attached to the suction surface (SS) of the blade, moving in the direction of the adjacent blade perpendicular to the SS, resulting in a flow blockage. With a further decrease in pressure, the SSPCVs grew in size and strength, accompanied by a rapid degradation in performance of the pump. The cavitation images and the corresponding circumferential pressure distributions showed that the lowest pressure point coincided with the SS corner. After this position, the pressure fluctuated as the cavitation intensity changed. The transient characteristics of SSPCV are a basis for revealing the instability mechanism of its evolution in the axial flow pump.

Numerical and Experimental Investigation of Tip Leakage Vortex Cavitation Patterns and Mechanisms in an Axial Flow Pump

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Desheng Zhang ◽  
Weidong Shi ◽  
Dazhi Pan ◽  
Michel Dubuisson
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Axial Flow ◽  
Tip Clearance ◽  
Cloud Cavitation ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump ◽  
Corner Vortex

The tip leakage vortex (TLV) cavitating flow in an axial flow pump was simulated based on an improved shear stress transport (SST) k-ω turbulence model and the homogeneous cavitation model. The generation and dynamics of the TLV cavitation throughout the blade cascades at different cavitation numbers were investigated by the numerical and experimental visualizations. The investigation results show that the corner vortex cavitation in the tip clearance is correlated with the reversed flow at the pressure side (PS) corner of blade, and TLV shear layer cavitation is caused by the interaction between the wall jet flow in the tip and the main flow in the impeller. The TLV cavitation patterns including TLV cavitation, tip corner vortex cavitation, shear layer cavitation, and blowing cavitation are merged into the unstable large-scale TLV cloud cavitation at critical cavitation conditions, which grows and collapses periodically near trailing edge (TE).

scholarly journals Experimental and Numerical Investigation on the Tip Leakage Vortex Cavitation in an Axial Flow Pump with Different Tip Clearances

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 935 ◽  
Author(s):  
Bin Xu ◽  
Xi Shen ◽  
Desheng Zhang ◽  
Weibin Zhang
Keyword(s):  
Axial Flow ◽  
Tip Clearance ◽  
Water Diversion ◽  
Tip Leakage Flow ◽  
Unstable Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Viscous Loss ◽  
Axial Flow Pump ◽  
Flow Pump

The tip gap existing between the blade tip and casing can give rise to tip leakage flow and interfere with the main flow, which causes unstable flow characteristics and intricate vortex in the passage. Investigation on the tip clearance effect is of great important due to its extensive applications in the rotating component of pumps. In this study, a scaling axial flow pump used in a south-north water diversion project with different sizes of tip clearances was employed to study the tip clearance effect on tip leakage vortex (TLV) characteristics. This analysis is based on a modified turbulence model. Validations were carried out using a high-speed photography technique. The tip clearance effect on the generation and evolution of TLV was investigated through the mean velocity, pressure, and vorticity fields. Results show that there are two kinds of TLV structures in the tip region. Accompanied by tip clearance increasing, the viscous loss in the tip area of the axial flow pump increases. Furthermore, the tip clearance effect on pressure distribution in the blade passage is discussed. Beyond that, the tip clearance effect on vortex core pressure and cavitation is studied.

scholarly journals Effect of Tip Clearance on Helico-Axial Flow Pump Performance at Off-Design Case

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1653
Author(s):  
Nengqi Kan ◽  
Zongku Liu ◽  
Guangtai Shi ◽  
Xiaobing Liu
Keyword(s):  
Optimization Design ◽  
Flow Characteristics ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
Hydraulic Loss ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

To reveal the effect of tip clearance on the flow behaviors and pressurization performance of a helico-axial flow pump, the standard k-ε turbulence model is employed to simulate the flow characteristics in the self-developed helico-axial flow pump. The pressure, streamlines and turbulent kinetic energy in a helico-axial flow pump are analyzed. Results show that the tip leakage flow (TLF) forms a tip-separation vortex (TSV) when it enters the tip clearance and forms a tip-leakage vortex (TLV) when it leaves the tip clearance. As the blade tip clearance increases, the TLV moves along the blade from the leading edge (LE) to trailing edge (TE). At the same time, the entrainment between the TLV and the main flow deteriorates the flow pattern in the pump and causes great hydraulic loss. In addition, the existence of tip clearance also increases the possibility of TLV cavitation and has a great effect on the pressurization performance of the helico-axial flow pump. The research results provide the theoretical basis for the structural optimization design of the helico-axial flow pump.

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

scholarly journals Study on the Performance Improvement of Axial Flow Pump’s Saddle Zone by Using a Double Inlet Nozzle

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1493
Author(s):  
Weidong Cao ◽  
Wei Li
Keyword(s):  
Flow Rate ◽  
Three Dimensional ◽  
Axial Flow ◽  
Rotating Stall ◽  
Stable Operation ◽  
Inlet Section ◽  
Pump Impeller ◽  
Rate Condition ◽  
Axial Flow Pump ◽  
Flow Pump

The operating range of axial flow pumps is often constrained by the onset of rotating stall. An improved method using a double inlet nozzle to stabilize the performance curve is presented in the current study; a single inlet nozzle and three kinds of double inlet nozzle with different rib gap widths at the inlet of axial flow pump impeller were designed. Three dimensional (3D) incompressible flow fields were simulated, and the distributions of turbulence kinetic energy and velocity at different flow rates located at the inlet section, as well as the pressure and streamline in the impeller, were obtained at the same time. The single inlet nozzle scheme and a double inlet nozzle scheme were studied; the experimental and numerical performance results show that although the cross section is partly blocked in the double inlet nozzle, the head and efficiency do not decline at stable operation flow rate. On small flow rate condition, the double inlet nozzle scheme effectively stabilized the head-flow performance, whereby the block induced by the backflow before the impeller was markedly improved by using a double inlet nozzle. It has also been found that the rib gap width impacts the efficiency curve of the axial flow pump.

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