Experimental and Numerical Investigation on Pressure Fluctuation of the Impeller in an Axial Flow Pump

2019 ◽  
Author(s):  
Xi Shen ◽  
Desheng Zhang ◽  
Bin Xu ◽  
Yongxin Jin ◽  
Xiongfa Gao
Keyword(s):  
Pressure Fluctuation ◽  
High Speed ◽  
Axial Flow ◽  
Suction Side ◽  
High Speed Photography ◽  
Detached Eddy Simulation ◽  
Transient Pressure ◽  
Unstable Flow ◽  
Axial Flow Pump ◽  
Flow Pump

Abstract The Detached Eddy Simulation (DES) has been used to simulate the pressure fluctuation of the impeller in an axial flow pump. The results were combined with experiments including high-speed photography and transient pressure measurements to investigate the unstable flow induced by tip leakage vortex (TLV). Numerical results show that maximum predictive error values of head is 2.9%, compared with experimental results. The pressure fluctuation at different monitoring points present a certain regularity, with 3 peaks and 3 troughs in a period, corresponding to the number of blades. The amplitude of pressure fluctuation at P1 (impeller inlet) is the highest among those monitoring points, where the amplitude decreases with the flow rates. The dominant frequency of pressure fluctuation at impeller under cavitation condition is the blade passing frequency (BPF). Besides, there are also N* = 6, 9, 12 and other more harmonic frequencies. The cavitation flow was analyzed with the pressure fluctuation of the blade tip. For the existence of the pressure difference between pressure side and suction side, the pressure at monitoring points change alternately. The amplitude of the fluctuation near tip is affected seriously by the cavitation bubbles, as the cavitation could is a low pressure region with unstable fluctuation.

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.

scholarly journals Analysis of the Formation Mechanism and Evolution of the Perpendicular Cavitation Vortex of Tip Leakage Flow in an Axial-Flow Pump for Off-Design Conditions

2021 ◽  
Vol 9 (10) ◽  
pp. 1045
Author(s):  
Hu Zhang ◽  
Jianbo Zang ◽  
Weidong Shi ◽  
Desheng Zhang
Keyword(s):  
Formation Mechanism ◽  
High Speed ◽  
Axial Flow ◽  
Axial Direction ◽  
High Speed Photography ◽  
Tip Leakage Flow ◽  
Origin And Evolution ◽  
Tip Leakage ◽  
Axial Flow Pump ◽  
Flow Pump

To understand the formation mechanism and evolution process of the perpendicular cavitation vortex (PCV) of an axial flow pump for off-design conditions, turbulent cavitating flows were numerically investigated using the rotation curvature-corrected shear stress transport (SST-CC) turbulence model and the Zwart–Gerber–Belamri cavitation model. In this work, the origin and evolution of a PCV were analyzed through a high-speed photography experiment and numerical simulation. The results showed that the PCV came from a secondary tip leakage vortex (S-TLV) and was aggregated by the action of the re-entrant jet, combined with the cavitation bubbles driven by the radial flow to form the cavitation vortex (CV). With the joint action of leakage jet lifting and TLV entrainment, the PCV was reoriented and gradually became perpendicular to the chord direction. Then, the PCV and TLV collided, mixed, and entrained, which formed a strong pressure pulsation. The PCV was gradually divided into upper and lower parts. One part was combined with the residual part of the TLV and flowed to the next blade, and the other part flowed out of the impeller area along the axial direction. At the same time, the generation, evolution, and dissipation of the PCV formed high pulsation amplitudes and frequencies in the middle and rear above the blade suction.

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 Evolution Characteristics of Suction-Side-Perpendicular Cavitating Vortex in Axial Flow Pump under Low Flow Condition

2021 ◽  
Vol 9 (10) ◽  
pp. 1058
Author(s):  
Lin Wang ◽  
Fangping Tang ◽  
Ye Chen ◽  
Haiyu Liu
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
High Speed ◽  
Axial Flow ◽  
Suction Side ◽  
Low Flow ◽  
Stage Of Development ◽  
Evolution Characteristics ◽  
Axial Flow Pump ◽  
Flow Pump

In order to study the evolution characteristics of suction-side-perpendicular cavitating vortex in an axial-flow pump under low flow conditions, model tests, high-speed imaging, and an SST-CC turbulence model were used to simulate the external characteristics and cavitation morphology of the pump. The evolution law of suction-side-perpendicular cavitating vortex (SSPCV) was revealed by turbulent kinetic energy, liutex vortex identification, and vorticity transport equation. The results show that the evolution of suction-side-perpendicular cavitating vortex at low cavitation number can be divided into three stages: generation, development, and breaking stage. In the generation stage, the turbulent kinetic energy, velocity gradient and vortex kinetic energy continue to increase, reaching the maximum at the early stage of development. Afterwards, due to the viscosity of the water, the vortex slowly dissipates and enters the stage of development. Finally, it is affected by the next blade and enters the breaking stage, which accelerates the dissipation of the vortex. The vortex stretching term and vortex expansion term are the main contributors to the vorticity. During the development of the vortex, the vorticity is mainly caused by the deformation of the fluid micelle. The breaking stage mainly affects the stretching term, and the Coriolis force term cannot be ignored in the rotating coordinates.

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.

Experimental Investigation of Blade Rows Interactions in Contra-Rotating Axial Flow Pump

2014 ◽  
Author(s):  
Linlin Cao ◽  
Hironori Honda ◽  
Hiroaki Yoshimura ◽  
Satoshi Watanabe ◽  
Akinori Furukawa
Keyword(s):  
Pressure Fluctuation ◽  
Axial Flow ◽  
Potential Interaction ◽  
Experimental Investigations ◽  
Cavitation Performance ◽  
Rotor Stator Interaction ◽  
Frequency Components ◽  
Axial Flow Pump ◽  
Theoretical Analyses ◽  
Flow Pump

As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, our prototype rotors designed with equal rotational speeds for both the front and the rear rotors was also confirmed with the strong potential interaction between two blade rows. In the present study, the experimental investigations were focused on the rotor-rotor interactions in the contra-rotating rotors under two rotational speed combinations, an equal speed and a different speed ones with the lower speed of rear rotor; the latter is determined aiming at relieved rotor-rotor interaction. As the major experimental approach, casing wall static pressure measurements were conducted at pressure taps covering from upstream to downstream of the both rotors, and the pressure fluctuation modes were investigated by the FFT analyses. By series of pressure taps with different peripheral locations prepared at several axial locations, the pressure fluctuation modes with frequencies non-synchronous to the BPF (blade passing frequency) components were recognized, and confirmed to be related to the rotor-rotor interaction on the basis of theoretical analyses on the rotor-stator interaction in conventional rotor-stator types.

An Investigation of the Vortex in a Submersible Axial Flow Pump Impeller

2015 ◽  
Vol 741 ◽  
pp. 481-485
Author(s):  
Hong Ming Zhang ◽  
Li Xiang Zhang
Keyword(s):  
Pressure Pulsation ◽  
Axial Flow ◽  
Suction Side ◽  
Transfer Model ◽  
Mass Transfer Model ◽  
Governing Equations ◽  
Pump Impeller ◽  
Axial Flow Pump ◽  
Volume Method ◽  
Flow Pump

The paper presents numerical simulation of the vortex in a submersible axial flow pump impeller using OpenFoam code. A mixture assumption and a finite rate mass transfer model were introduced to analyze vortex. The finite volume method is used to solve the governing equations of the mixture model and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the cavitation may occur on the lower portion of impeller suction side. And the blade channel vortex will be formed in the impeller. It can induce the pressure pulsation in the impeller and can result in reduced efficiency of the submersible axial flow pump.

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