Experimental Investigation of Tip Cavitating Vortices in Axial-Flow Pump

2017 ◽  
Author(s):  
Desheng Zhang
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Axial Flow ◽  
Operating Conditions ◽  
High Speed Imaging ◽  
Cavitation Performance ◽  
Stable Operating ◽  
Wide Range ◽  
Axial Flow Pump ◽  
Flow Pump

The primary goal of this work focuses on the cavitating vortices in the tip region of an axial-flow pump with 3 and 4 blades mainly based on the high-speed imaging experiments, with special attention on the trajectory and dynamics of a large-scale cavitation structure. The hydraulic and cavitation performance between two impellers were compared, and it can be found that the model with 4 blades has a relative wide range of stable operating conditions as well as the better anti-cavitation ability. By the analysis of the cavitation curves, it confirms that the highly unsteady tip cavitation cloud near the blade trailing edge should be responsible for the severe degradation of the performance. According to the detailed study on the cavitation evolution in the two impellers, it is observed that the trajectory of tip cavitating vortices for different flow rates seems very similar determined by the operating conditions. However, the dynamics varies significantly, which is associated with the blade loading and flow passage width.

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.

Performance Study of a Mixed Flow Impeller Covering an Unsteady Flow Field

1992 ◽  
Vol 206 (2) ◽  
pp. 83-93 ◽  
Author(s):  
S Sarkar
Keyword(s):  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Performance Study ◽  
Mixed Flow ◽  
Pump Impeller ◽  
Wide Range ◽  
Reversal Flow ◽  
Flow Through ◽  
Flow Pump

The results presented here are part of a detailed programme measuring the aerodynamics of a high specific speed mixed flow pump impeller over a wide range of operating conditions, including its behaviour in the unsteady stalled regime. The aim is to elucidate the physics of the flow through such an impeller. The noticeable features are the formation of part-span rotating stall cells having no periodicity and organized structure at reduced flow and also the shifting positions of reversal flow pockets as the flowrate changes. Measurements of loss and its variation with span-wise positions and flowrates enable the variation of local efficiency to be determined. The overall flow picture is similar to that expected in an axial flow impeller, though the present impeller displays a narrow stall hysteresis loop almost right through its operating range.

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.

scholarly journals Improvement of the Efficiency of the Axial-Flow Pump at Part Loads due to Installing Outlet Guide Vanes Mechanism

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Fan Yang ◽  
Hao-ru Zhao ◽  
Chao Liu
Keyword(s):  
Prediction Model ◽  
Flow Rate ◽  
High Efficiency ◽  
Guide Vane ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Ann Model ◽  
Axial Flow Pump ◽  
Flow Pump

In order to investigate the influence of adjustable outlet guide vane on the hydraulic performance of axial-flow pump at part loads, the axial-flow pump with 7 different outlet guide vane adjustable angles was simulated based on the RNG k-ε turbulent model and Reynolds time-averaged equations. The Vector graphs of airfoil flow were analyzed in the different operating conditions for different adjustable angles of guide vane. BP-ANN prediction model was established about the effect of adjustable outlet guide vane on the hydraulic performance of axial-flow pump based on the numerical results. The effectiveness of prediction model was verified by theoretical analysis and numerical simulation. The results show that, with the adjustable angle of guide vane increasing along clockwise, the high efficiency area moves to the large flow rate direction; otherwise, that moves to the small flow rate direction. The internal flow field of guide vane is improved by adjusting angle, and the flow separation of tail and guide vane inlet ledge are decreased or eliminated, so that the hydraulic efficiency of pumping system will be improved. The prediction accuracy of BP-ANN model is 1%, which can meet the requirement of practical engineering.

scholarly journals Simulation of cavitation performance of an axial flow pump with inlet guide vanes

2016 ◽  
Vol 8 (6) ◽  
pp. 168781401665158 ◽  
Author(s):  
Weimin Feng ◽  
Qian Cheng ◽  
Zhiwei Guo ◽  
Zhongdong Qian
Keyword(s):  
Axial Flow ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Cavitation Performance ◽  
Axial Flow Pump ◽  
Flow Pump

PIV Measurements and CFD Analysis in an Axial-Flow Pump

2007 ◽  
Author(s):  
Fang-Ping Tang ◽  
Chao Liu ◽  
Ji-Ren Zhou ◽  
Hua Yang ◽  
Li Cheng
Keyword(s):  
Flow Rate ◽  
Outer Part ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Separation Flow ◽  
Mean Velocity ◽  
Piv Measurements ◽  
Axial Flow Pump ◽  
Flow Pump

In this study, an axial flow pump impeller without guide vanes is experimentally investigated. The impeller used in the experiments consists of four blades. The particle image velocimetry technique and a five-hole probe have been used. Measurements of flow velocities in the outer part of the impeller have been made. PIV measurements have been realized in 12 meridian planes between blade-to-blade for design and off-design operating conditions. The meridian velocity is obtained with phase averaged method and the total circumferential mean velocity is obtained with an arithmetical average over the 12 circumferential data. The calculation is based on the CFX-TASC flow CFD code solving the three-dimensional Reynolds-averaged Navier-Stokes equation with RNG k–ε model of turbulence. The paper focuses on the comparisons of the results. Difference for the flow field between numerical and experimental results is small at large and design flow rate, while big difference occurs at small flow rate. It indicates that the numerical model is not suitable for separation flow.

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.

Rotor/Stator Interactions Study under Different Operating Condition in Axial Flow Pump

2013 ◽  
Vol 456 ◽  
pp. 168-172 ◽  
Author(s):  
Wei Dong Shi ◽  
Su Qing Wu ◽  
Jie Yao
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
Operating Condition ◽  
Simulation Based ◽  
Rotor Stator Interaction ◽  
Unsteady Simulation ◽  
Fluctuation Amplitude ◽  
Axial Flow Pump ◽  
Flow Pump ◽  
Interaction Phenomenon

Rotor/Stator interaction in axial-flow pump is the main reason for pressure fluctuates, which impacts on operating security of axial flow pump. In order to study Rotor/Stator interaction phenomenon in axial flow pump, TJ04-ZL-02 hydraulic axial flow pump model is investigated under different operating condition by unsteady simulation based on k-ω turbulence model. Numerical results show that: different flow operating conditions will lead to different Rotor/Stator interaction phenomenon, and also different pressure fluctuation. Fluctuation amplitude in design operating condition is smaller than off design operating condition. So the study proves that pump running in the design operating conditions has important beneficial to the pump operational stability.

Tip Clearance and Tip Vortex Cavitation in an Axial Flow Pump

1997 ◽  
Vol 119 (3) ◽  
pp. 680-685 ◽  
Author(s):  
R. Laborde ◽  
P. Chantrel ◽  
M. Mory
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception ◽  
Rotating Machine ◽  
Axial Flow Pump ◽  
Gap Height ◽  
Flow Pump

A combined study of tip clearance and tip vortex cavitations in a pump-type rotating machine is presented. Cavitation patterns are observed and cavitation inception is determined for various gap heights, clearance and blade geometries, and rotor operating conditions. An optimum clearance geometry is seen to eliminate clearance cavitation when the clearance edge is rounded on the blade pressure side. The gap height has a strong effect on clearance cavitation inception, but the trends vary considerably when other parameters are also modified. The gap height and clearance geometry have less influence on tip vortex cavitation but forward and backward blade skew is observed to reduce and increase tip vortex cavitation, respectively, as compared to a blade with no skew.

scholarly journals CFD numerical simulation of sand-contained cavitation characteristics of axial-flow pump

2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110327
Author(s):  
Peng Lin ◽  
Dong Hu ◽  
Jing-Man Lu ◽  
Shu Wang
Keyword(s):  
Particle Size ◽  
Flow Pattern ◽  
Great Influence ◽  
Axial Flow ◽  
Internal Flow ◽  
Sediment Concentration ◽  
Clean Water ◽  
Cavitation Performance ◽  
Axial Flow Pump ◽  
Flow Pump

To study the effect of sediment on the cavitation in the axial-flow pump, the method of CFD is employed to experiment on the internal flow field of the pump in the case of cavitation in clean water and sandy water separately. The calculation is done with different particle sizes and sediment concentrations. The results show that as the sediment concentration increases, the vortex range and cavitation area of the blade will further increase, and the flow pattern in the impeller becomes more disordered. The mechanism of action of particle size on cavitation is similar to that of sediment concentration. However, cavitation in clean water is quite different from that in sandy water in that the cavitation value and range in sandy water are significantly larger than that in clean water. By contrast, the particle size has little effect on the cavitation value and range. It proves that particle size does not have a great influence on cavitation distribution, but sediment concentration is the main factor affecting the cavitation performance of the pump. Moreover, sediment will disrupt the internal flow pattern of the pump, promote the development of cavitation and further reduce the cavitation performance of the pump.

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