scholarly journals Study on a Horizontal Axial Flow Pump during Runaway Process with Bidirectional Operating Conditions

2021 ◽  
Author(s):  
Kan Kan ◽  
Qingying Zhang ◽  
Zhe Xu ◽  
Huixiang Chen ◽  
Yuan Zheng ◽  
...  
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
Vof Model ◽  
Torque Curve ◽  
The Difference ◽  
Axial Flow Pump ◽  
Pump Stations ◽  
Short Time ◽  
Flow Pump ◽  
Runaway Process

Abstract The ultra-low head pump stations often have bidirectional demand of water delivery, so there is a risk of runaway accident occurring in both conditions. To analyze the difference of the runaway process under forward runaway condition (FRC) and backward runaway condition (BRC), the whole flow system of a horizontal axial flow pump is considered. The Shear-Stress Transport (SST) k-ω model is adopted and the volume of fluid (VOF) model is applied to simulate the water surface in the reservoirs. Meanwhile, the torque balance equation is introduced to obtain the real time rotational speed, then the bidirectional runaway process of the pump with the same head is simulated. Additionally, the vortex transport equation is proposed to compare the contribution of vortex stretching and vortex dilatation terms. According to the changing law of the impeller torque, the torque curve can be divided into five stages: the drop, braking, rising, convergence and runaway stages. By comparison, the rising peak value of torque under FRC is significantly higher than that under BRC in the rising stage. Simultaneously, through the short time Fourier transform (STFT) method, the amplitude of torque pulsation is obviously different between FRC and BRC. The analysis reveals that the flow impact on blade surface increases the pressure difference between the two sides of the blade in braking condition, which leads to the torque increase in the rising stage. Moreover, the pulsation amplitude of torque is mainly affected by the integrity of the vortex rope.

scholarly journals Study on a horizontal axial flow pump during runaway process with bidirectional operating conditions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kan Kan ◽  
Qingying Zhang ◽  
Zhe Xu ◽  
Huixiang Chen ◽  
Yuan Zheng ◽  
...  
Keyword(s):  
Axial Flow ◽  
Rotation Frequency ◽  
Operating Conditions ◽  
Suction Surface ◽  
Pulsation Amplitude ◽  
Vof Model ◽  
Axial Flow Pump ◽  
Pump Stations ◽  
Flow Pump ◽  
Runaway Process

AbstractThe ultra-low head pump stations often have bidirectional demand of water delivery, so there is a risk of runaway accident occurring in both conditions. To analyze the difference of the runaway process under forward runaway condition (FRC) and backward runaway condition (BRC), the whole flow system of a horizontal axial flow pump is considered. The Shear-Stress Transport (SST) k–ω model is adopted and the volume of fluid (VOF) model is applied to simulate the water surface in the reservoirs. Meanwhile, the torque balance equation is introduced to obtain the real time rotational speed, then the bidirectional runaway process of the pump with the same head is simulated. In addition, the vortex transport equation and swirl number are proposed to reveal the flow characteristics during the runaway process. The results show that the runaway process can be divided into five stages: the drop, braking, rising, convergence and runaway stages, according to the changing law of torque curve. In the rising stage, the pressure difference on the blade surface continues to increase, which contributes to the abnormal torque increase. In this stage, the flow hits the pressure surface (PS) at a faster speed enlarging the pressure on PS, and the flow separation takes place on the suction surface (SS) weakening the pressure on SS. During the convergence and runaway stage, the pulsation amplitude of torque and axial force under FRC is obviously larger than those under BRC. This is because the rotation frequency of the vortex rope is the same as main pressure fluctuation frequency in impeller under FRC, which enhances the pulsation amplitude. Whereas the vortices are broken due to the inhibitive effect from guide vanes under BRC.

scholarly journals Investigation into the Influence of Division Pier on the Internal Flow and Pulsation in the Outlet Conduit of an Axial-Flow Pump

2021 ◽  
Vol 11 (15) ◽  
pp. 6774
Author(s):  
Fan Yang ◽  
Dongjin Jiang ◽  
Tieli Wang ◽  
Pengcheng Chang ◽  
Chao Liu ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Pressure Pulsation ◽  
Axial Flow ◽  
Hydraulic Loss ◽  
Main Frequency ◽  
Starting Position ◽  
The Difference ◽  
Axial Flow Pump ◽  
Outlet Conduit ◽  
Flow Pump

The outlet conduit is an important construction connecting the outlet of the pump guide vane and the outlet pool; in order to study the hydraulic performance of the straight outlet conduit of the axial-flow pump device, this paper adopts the method of numerical simulation and analyzes the influence of the division pier on the pressure and velocity distribution inside and near the wall of the straight outlet conduit based on three design schemes. Four pressure pulsation measuring points were arranged in the straight outlet conduit, and the low-frequency pulsation characteristic information inside the straight outlet conduit with and without the division pier was extracted by wavelet packet reconstruction. The results show that the addition of a division pier has an effect on the hydraulic loss, near-wall pressure and velocity distribution in the straight outlet conduit. A small high-pressure zone is formed near the wall at the starting position of the division pier, and a large high-speed zone is formed on the left side at the starting position of the division pier. The length of the division pier has no significant effect on the flow distribution of the straight outlet conduit and the pressure and velocity distribution near the wall. Under different working conditions, each monitoring point has the maximum energy in the sub-band (0~31.25 Hz). With the increase of the flow rate, the total pressure energy of the straight outlet conduit decreases gradually. Under each condition, the difference of the energy proportion of the horizontal monitoring points of the straight outlet conduit is small, and the difference of the energy proportion of the two monitoring points at the top and bottom of the outlet channel is relatively large. The energy of the two monitoring points in the straight outlet conduit with a division pier is smaller than that of the two monitoring points in the straight outlet conduit without a division pier. There are differences in the main frequency and the power spectrum corresponding to the main frequency of the monitoring points in the straight outlet conduit, and the reasonable setting of the division pier is conducive to reducing the pressure pulsation of the flow in the straight outlet conduit and is beneficial to the safe and stable operation of the pump device.

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.

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.

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.

Flow Characteristics of High-Efficient Axial Flow Pump System

2015 ◽  
Author(s):  
Chao Liu ◽  
Fan Yang ◽  
Yan Jin ◽  
Hua Yang
Keyword(s):  
Flow Characteristics ◽  
Axial Flow ◽  
Internal Flow ◽  
Operating Conditions ◽  
Optimum Operating ◽  
Hydraulic Loss ◽  
Pump System ◽  
High Efficient ◽  
Axial Flow Pump ◽  
Flow Pump

Three-dimensional flow-fields in a high-efficient axial flow pump system were simulated by CFD to further study the internal flow characteristics. The internal flow patterns of the pump system were obtained at large, small and optimum operating conditions. The highest efficiency of pump system measured and calculated are 82.57% and 81% respectively at blade angle 0°. For the suction passage, the axial velocity distribution uniformity reach 97.51%, and the hydraulic loss is 0.039m, the pipe efficiency calculated is 98.5% at the optimum operating conditions. The maximum velocity is 1.429 m/s in the range of operating conditions, which meet the requirement of National standard. The performances predicted were compared with measurement results. It was found that the calculated results agree well with the measured results. The overall flow pattern of the pump system is uniform and smooth, and the hydraulic loss is very small which gives the excellent hydraulic performances of pump system.

Unsteady Three-Dimensional Flow Phenomena in an Axial Flow Pump at Different Operating Points

2008 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Flow Fields ◽  
Operating Conditions ◽  
Three Dimensional Flow ◽  
Design Point ◽  
Part Load ◽  
Dimensional Flow ◽  
Axial Flow Pump ◽  
Flow Pump

In highly loaded axial flow pumps considerable changes of the flow behavior are known when altering the flow rate from design point operation to part load operation. The flow structure which is changing from stable operating conditions to stalled flow conditions has been investigated experimental by Kosyna and Stark. The measured results are compared to results obtained by numerical simulations in a previous paper of the authors. Time dependent three dimensional flow fields in this axial flow pump have been investigated by unsteady Reynolds averaged Navier-Stokes simulations. The time resolved flow fields are compared to the time averaged results of the measurements for the design point and also for part load operating conditions. The change in the vortex structure induced by the tip leakage flow is investigated in detail for different conditions of operation. Also the part load recirculation vortex dominating the rotor tip flow at deep stall conditions as well as the cross passage vortex is visualized by evaluating the numerical results.

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.

scholarly journals Numerical Simulation and Experiment of the Effects of Blade Angle Deviation on the Hydraulic Characteristics and Pressure Pulsation of an Axial-Flow Pump

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Lijian Shi ◽  
Jun Zhu ◽  
Yao Yuan ◽  
Fangping Tang ◽  
Penglan Huang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Pulsation ◽  
Low Frequency ◽  
Axial Flow ◽  
Stable Operation ◽  
Blade Angle ◽  
Angle Deviation ◽  
Axial Flow Pump ◽  
Pump Stations ◽  
Flow Pump

Inadequate blade angle adjustment or manufacturing errors will cause inconsistencies in the blade angle of an axial-flow pump. In this study, the hydrodynamic characteristics of an axial-flow pump with inconsistent blade angle are investigated by analyzing hydraulic performance and pressure pulsation. The analysis is conducted by performing a numerical simulation combined with a model test. Results show that, relative to the case without blade angle deviation, the case with blade angle deviation exhibits changes in the periodicity of the flow field in the impeller. Such changes result in uneven pressure changes in the impeller passage. The pressure pulsation induced by the blade angle deviation is mainly low-frequency pulsation; that is, it is twice the rotation frequency. The amplitude of the main frequency pulsation is 1.5–3 times that of the blade without angle deviation. This low frequency that dominates the whole pump device easily causes the vibration and weakens the safety and stability of the pump. The blade angle deviation exerts great influence on the unsteady characteristics. Hence, blade angle deviation seriously affects the safe and stable operation of axial-flow pumps and pump stations.

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