Research on the Influence of Tip Clearance of Axial-Flow Pump on Energy Characteristics under Pump and Turbine Conditions

In order to study the influence of tip clearance on the performance and energy dissipation of the axial-flow pump and the axial-flow pump as a turbine, and find the location of high dissipation rate, this study took an axial-flow pump model as its research object and designed four tip radial clearance schemes (0, 0.2, 1 and 2 mm). The unsteady calculation simulation of each tip clearance scheme was carried out based on CFD technology. The calculated results were compared with the experimental results, and the simulation results were analyzed using entropy production analysis theory. The results showed that, under both an axial-flow pump and axial-flow pump as turbine operating conditions, increasing the blade tip clearance led to a decrease in hydraulic performance. Compared with the 0 mm clearance, the maximum decreases in pump efficiency, head and shaft power under 2 mm tip clearance were 15.3%, 25.7% and 12.3% under the pump condition, and 12.7%, 18.5% and 28.8% under the turbine condition, respectively. Under the axial-flow pump operating condition, the change in blade tip clearance had a great influence on the total dissipation of the impeller, guide vane and outlet passage, and the maximum variation under the flow rate of 1.0 was 53.9%, 32.1% and 54.2%, respectively. Under the axial-flow pump as a turbine operating condition, the change in blade tip clearance had a great influence on the total dissipation of the impeller and outlet passage, the maximum variation under the flow rate of 1.0 was 22.7% and 17.4%, respectively. Under the design flow rate condition, with the increase in tip clearance, the dissipation rate of the blade surface showed an increasing trend under both the axial-flow pump and axial-flow pump as turbine operating conditions, and areas of high dissipation rate were generated at the rim and clearance.

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

Volume 1B, Symposia: Fluid Machinery; Fluid Power; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Flow Manipulation and Active Control: Theory, Experiments and Implementation; Fundamental Issues and Perspectives in Fluid Mechanics ◽

10.1115/fedsm2013-16058 ◽

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.

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

Mathematical Problems in Engineering ◽

10.1155/2016/6375314 ◽

2016 ◽

Vol 2016 ◽

pp. 1-10 ◽

Cited By ~ 2

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.

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PIV Measurements and CFD Analysis in an Axial-Flow Pump

Volume 2: Fora, Parts A and B ◽

10.1115/fedsm2007-37527 ◽

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.

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Tip Clearance and Tip Vortex Cavitation in an Axial Flow Pump

Journal of Fluids Engineering ◽

10.1115/1.2819298 ◽

1997 ◽

Vol 119 (3) ◽

pp. 680-685 ◽

Cited By ~ 45

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.

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

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650918812541 ◽

2018 ◽

Vol 233 (4) ◽

pp. 476-488 ◽

Cited By ~ 4

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.

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Stall inception phenomena in a single-stage axial-flow pump

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1243/095765003322315531 ◽

2003 ◽

Vol 217 (4) ◽

pp. 471-479 ◽

Cited By ~ 17

Author(s):

I Goltz ◽

G Kosyna ◽

U Stark ◽

H Saathoff ◽

S Bross

Keyword(s):

Axial Flow ◽

Wall Pressure ◽

Operating Conditions ◽

Single Stage ◽

Rotor Blades ◽

Tip Clearance ◽

Stall Inception ◽

Oil Flow ◽

Axial Flow Pump ◽

Flow Pump

The paper describes an experimental investigation on stall inception phenomena in a single-stage axial-flow pump, utilizing an oil flow technique and two different photo techniques. Moreover, the unsteady casing wall pressure was measured. Representative results are shown and discussed: the pump characteristic for two different NPSH values, selected oil flow pictures of the casing wall and the rotor blades, the wall pressure distribution at design, selected pictures of the cavitating core of the tip clearance vortex at stable and unstable operating conditions and the visualization of a cross-passage vortex as a deep stall phenomenon. These results allow a number of key features of the stall inception process to be identified and to be followed along the unstable part of the pump characteristic.

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

Processes ◽

10.3390/pr9091653 ◽

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.

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Interrelationship Between the Efficiency Characteristics and the Pressure Head Gradients Among Axial Flow Pumps

Volume 2: Design, Construction, and Operation Innovations; Compression and Pump Technology; SCADA, Automation, and Measurement; System Simulation; Geotechnical and Environmental ◽

10.1115/ipc1996-1892 ◽

1996 ◽

Author(s):

Takaharu Tanaka

Keyword(s):

Cross Section ◽

Flow Rate ◽

Axial Flow ◽

Internal Flow ◽

Pressure Head ◽

Design Flow ◽

Discharge Valve ◽

Head Gradient ◽

Axial Flow Pump ◽

Flow Pump

There is a correlation between the efficiency of the pump to the head produced. On the axial flow pump, whose efficiency characteristic is favorable, the pressure head gradient between the impeller inlet and the outlet sections, at an equivalent flow rate, may become larger than that for the less favorable axial flow pump. This fundamental interrelation may be held in the flow passage regardless to the flow rate whichever they are operated at design or off design flow rate. There may be a direct correlation between the efficiency of an axial flow pump and the ratio of the discharge valve cross section divided by the pipeline cross section. The smaller this ratio is the better the pressure head gradient is for the same flow rates. This ratio may be useful to estimate relative grade of heads, pressure head gradients, internal flow conditions, and efficiency characteristics among axial flow pumps.

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

Water ◽

10.3390/w12051493 ◽

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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