scholarly journals Investigation on the Transient Characteristics of Self-Priming Pumps with Different Hub Radii

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 311
Author(s):  
Hao Chang ◽  
Shiming Hong ◽  
Chuan Wang ◽  
Guangjie Peng ◽  
Fengyi Fan ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Radial Force ◽  
Force Distribution ◽  
Surface Load ◽  
Blade Surface ◽  
Load Pressure ◽  
Transient Characteristics ◽  
Power Capability

Self-priming pumps, important fluid equipment, are widely used in the disaster relief and emergency fields. Meanwhile, the impeller is the only rotational unit of the self-priming pump, which plays an essential part in the power capability of the pump. In this paper, impellers with different hub radii are proposed; by comparing the internal flow characteristics, blade surface load, pressure pulsation characteristics, and radial force distribution of each scheme, the relationship between transient characteristics and hub radius is obtained. The results present that the impeller with a large hub radius can not only weaken the pressure pulsation, blade surface load, and radial force distribution, but also improve the ability of the blade to work on the internal flow field. Finally, the relevant hydraulic experiment is conducted, with the difference between the experiment and calculation below 3%, which ensures the accuracy of the calculation results.

scholarly journals Analysis of Internal Flow Characteristics of a Startup Pump Turbine at the Lowest Head under No-Load Conditions

2021 ◽  
Vol 9 (12) ◽  
pp. 1360
Author(s):  
Wei Wang ◽  
Xi Wang ◽  
Zhengwei Wang ◽  
Mabing Ni ◽  
Chunan Yang
Keyword(s):  
High Speed ◽  
Pressure Pulsation ◽  
Working Condition ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Operating Conditions ◽  
Small Range ◽  
Pressure Balance ◽  
Pump Turbine

The instability of the no-load working condition of the pump turbine directly affects the grid connection of the unit, and will cause vibration and damage to the components of the unit in severe cases. In this paper, a three-dimensional full flow numerical model including the runner gap and the pressure-balance pipe was established. The method SST k-ω model was used to predict the internal flow characteristics of the pump turbine. The pressure pulsation of the runner under different operating conditions during the no-load process was compared. Because the rotation speed, flow rate, and guide vane opening of the unit change in a small range during the no-load process, the pressure pulsation characteristics of the runner are basically the same. Therefore, a working condition was selected to analyze the transient characteristics of the flow field, and it was found that there was a high-speed ring in the vaneless zone, and a stable channel vortex was generated in the runner flow passage. Analyzing the axial water thrust of each part of the runner, it was found that the axial water thrust of the runner gap was much larger than the axial water thrust of the runner blades, and it changed with time periodically. It was affected by rotor stator interaction. The main frequency was expressed as a multiple of the number of guide vanes, that is, vanes passing frequency, 22fn. During the entire no-load process, the axial water thrust of the runner changed slowly with time and fluctuated slightly.

Influence of non-uniform inflow on unsteady internal flow characteristics of waterjet pump

2021 ◽  
Author(s):  
Chao Liu ◽  
Hongxun Chen ◽  
Zheng Ma
Keyword(s):  
High Speed ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Energy Performance ◽  
Hydrodynamic Characteristics ◽  
Area Formula ◽  
Low Speed ◽  
Waterjet Pump

Waterjet propulsion has many advantages when operating at high-speed conditions. As a special way of navigation, it is mostly used in high-speed ships and shallow draft ships. In this paper, a mixed-flow waterjet pump was taken as the research object. For the two cases of non-uniform inflow and uniform inflow, a modified RANS/LES method was adopted for unsteady calculation of the whole channel, aiming at investigating the influence mechanism of the non-uniform inflow on the energy performance and pressure pulsation characteristics of the waterjet pump. The hydrodynamic characteristics of the waterjet pump were comprehensively analyzed such as head, efficiency, axial-force, internal flow and pressure pulsation. It is found that the non-uniform inflow will reduce the external characteristics of the waterjet pump and lead to the huge fluctuation of energy performance with time. Low-speed swirls occur locally in the intake duct for non-uniform inflow, in which condition the vorticity is much higher than that for uniform inflow. In terms of the low-speed area, [Formula: see text] and [Formula: see text], the values under non-uniform inflow condition are generally larger than those under uniform flow condition when in the impeller and guide vane zone. The dominant frequencies of pressure pulsation are, respectively, [Formula: see text], 7[Formula: see text] and 4[Formula: see text] in the intake duct, impeller and diffuser, which are almost consitent for the two cases. However, the frequency features are more diverse, and the amplitudes corresponding to the same frequencies are more intense for non-uniform inflow.

scholarly journals A Comparative Study on Centrifugal Pump Designs and Two-Phase Flow Characteristic under Inlet Gas Entrainment Conditions

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 65 ◽  
Author(s):  
Qiaorui Si ◽  
Gérard Bois ◽  
Minquan Liao ◽  
Haoyang Zhang ◽  
Qianglei Cui ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Phase Flow ◽  
Water Mixture ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Void Fractions

Capability for handling entrained gas is an important design consideration for centrifugal pumps used in petroleum, chemistry, nuclear applications. An experimental evaluation on their two phase performance is presented for two centrifugal pumps working under air-water mixture fluid conditions. The geometries of the two pumps are designed for the same flow rate and shut off head coefficient with the same impeller rotational speed. Overal pump performance and unsteady pressure pulsation information are obtained at different rotational speeds combined with various inlet air void fractions (α0) up to pump stop condition. As seen from the test results, pump 2 is able to deliver up to 10% two-phase mixtures before pump shut-off, whereas pump 1 is limited to 8%. In order to understand the physics of this flow phenomenon, a full three-dimensional unsteady Reynolds Average Navier-Stokes (3D-URANS) calculation using the Euler–Euler inhomogeneous method are carried out to study the two phase flow characteristics of the model pump after corresponding experimental verification. The internal flow characteristics inside the impeller and volute are physically described using the obtained air distribution, velocity streamline, vortex pattern and pressure pulsation results under different flow rates and inlet void fractions. Pump performances would deteriorate during pumping two-phase mixture fluid compared with single flow conditions due to the phase separating effect. Some physical explanation about performance improvements on handing maximum acceptable inlet two phase void fractions capability of centrifugal pumps are given.

Investigation on performance of a centrifugal pump with multi-malfunction

2020 ◽  
pp. 146134842094234
Author(s):  
Minggao Tan ◽  
Youdong Lu ◽  
Xianfang Wu ◽  
Houlin Liu ◽  
Xiao Tian
Keyword(s):  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Radial Force ◽  
Design Flow ◽  
Vibration Level ◽  
Measuring Point ◽  
Flow Pressure ◽  
Simulation Results ◽  
Peak Value

Herein, the performance and inner flow characteristics of a single-stage single-suction centrifugal pump with multi-malfunctions (broken blade and seal ring abrasion) were determined through tests and numerical simulation. The vibration, inner flow, pressure, and radial force of the centrifugal pump were analyzed in detail. Compared with those of a normal pump, the head and efficiency of the pump with multi-malfunctions decreased by 10.56 and 10.09%, respectively, under the design flow rate. The general vibration level most significantly increased at the foot of the pump. The axial passing frequency of each measuring point increased in varying degrees, and new characteristic frequencies appeared at 5, 2, and 3 axial passing frequencies. The simulation results showed that in the pump with multi-functions, the pressure gradient near the broken blade was distinctly reduced, and the periodicity of the impeller radial force became weaker and more concentrated, thus exhibiting different performance than the normal pump. The peak-to-peak value of the pressure pulsation near the tongue increased by 8.5%, whereas that at the pump outlet decreased by 6.8%. Moreover, a vortex appeared at the inlet and another at the middle of the impeller, and the low-pressure zone near the impeller inlet expanded to the middle of the impeller. The results of this work can be used as reference for pump fault diagnosis.

scholarly journals Effects of Impeller Diameter on High-Speed Rescue Pump

2017 ◽  
Vol 2017 ◽  
pp. 1-15
Author(s):  
Yuxing Bai ◽  
Fanyu Kong ◽  
Bin Xia ◽  
Fei Zhao ◽  
Yingying Liu
Keyword(s):  
High Speed ◽  
Performance Test ◽  
Pressure Pulsation ◽  
Rate Increase ◽  
Flow Characteristics ◽  
Radial Force ◽  
Hydraulic Loss ◽  
Ansys Software ◽  
Acceptable Error ◽  
Flow Rate Increase

Impeller diameter is a crucial design parameter of high-speed rescue pumps because it affects the performance and inner flow characteristics of these pumps. In this study, a pump with an impeller diameter of 248 mm was modeled and its performance was tested. Numerical simulations were conducted under steady and unsteady states, in which the sizes of the impeller diameters were designated as 248 mm (original), 235.6 mm (5% trimmed), 223.2 mm (10% trimmed), and 210.8 mm (15% trimmed). ANSYS software was used to test the shear stress transport (SST k-ω) of the four models, and results agreed well with experimental data. Diameter size affected impeller characteristics in both steady and unsteady states. Subsequently, the differences in performance, hydraulic loss, pressure pulsation, and radial force of the impellers were evaluated. In the performance test, the head and efficiency of the pump decreased as impeller diameter was reduced. The result trends are in accordance with the trim law within the acceptable error range. In terms of hydraulic loss, the impeller and diffuser vane components presented opposite trends with flow rate increase. Finally, in terms of pressure pulsation and radial force, the amplitude diminished while periodicity improved as impeller diameter decreased.

scholarly journals Dynamic simulation of inner flow in a photovoltaic pump based on Simulink and CFD

2021 ◽  
Author(s):  
Xianfang Wu ◽  
Heyu Ye ◽  
Minggao Tan ◽  
Houlin Liu
Keyword(s):  
Solar Radiation ◽  
Pressure Pulsation ◽  
Transient Flow ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Maximum Error ◽  
Pump System ◽  
Impeller Outlet ◽  
Pump Flow Rate

Abstract To study the internal flow characteristics of the photovoltaic pump under the transient change of the solar radiation, the simulation algorithm of the photovoltaic pump system was established by MATLAB/Simulink and CFD for the first time and the results were validated by the test. Firstly, the change rule of pump flow rate and rotation speed under transient solar radiation was obtained by Simulink. Then the results of the change rule were transformed into the boundary condition of CFD by CEL function and the transient flow field in the photovoltaic pump was obtained. The internal flow characteristics and pressure pulsation in the pump were analyzed when the solar radiation increases or decreases transiently. The results demonstrate that the numerical calculation can provide accurate prediction for the characteristics of internal flow in the pump. The numerical results are closed to experimental results, the minimum error of pressure is 0.93% and the maximum error is 1.78%. When the solar radiation increases transiently, the low pressure area at the impeller inlet gets larger obviously and the jet-wake at the impeller outlet becomes more obvious. The pressure pulsation in impeller gradually increases and becomes stable after 0.6 s. The pressure from the impeller outlet to guide vane outlet is stable at 123 kPa. When the solar radiation decreases transiently, the pressure in the impeller takes 1.6 s to be stable. Larger pressure pulsation occurs from the impeller outlet to the guide vane inlet and the maximum differential pressure is 10 kPa. Compared with the transient increase of solar radiation, the pressure in the impeller takes more 0.2 s to stabilize when the solar radiation transient decreases. Meanwhile, the results in this paper can provide references for other transient characteristics research.

scholarly journals Effect of eccentricity on radial force and cavitation characteristics in the reactor coolant pump

2020 ◽  
pp. 312-312
Author(s):  
Yuanyuan Zhao ◽  
Xiuli Wang ◽  
Rongsheng Zhu
Keyword(s):  
Nuclear Power ◽  
Nuclear Reactor ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Radial Force ◽  
Asymmetric Structure ◽  
Two Phase ◽  
Coolant Pump ◽  
Cavitation Inception ◽  
Reactor Coolant

Nuclear reactor coolant pump as one of the most critical equipment is the only one rotating equipment in first loop system of nuclear power plant. Due to the asymmetric structure of the pump body, especially the existence of outlet segment lead to a certain of radial force, the magnitude of radial force directly affects the work stability of the reactor coolant pump. The nuclear reactor coolant pump could stability work under those transient complex conditions is an important index of its performance. To study the cavitation characteristics and radial force of reactor coolant pump on transient cavitation, a prototype pump and those exhibiting different gravity center offsets are analyzed numerically with CFD software ANSYS CFX by employing RNG k-? model and two-fluid two-phase flow model. Through the experiment-combined simulation, the variations of cavitation characteristics and radial force of the reactor coolant pump under different eccentricities are characterized. As revealed from the results, the flow characteristics of the internal flow field of the nuclear main pump change after the axis is offset by different distance. The influence of eccentricity on the cavitation of the nuclear main pump is mainly manifested at the impeller inlet from cavitation inception to severe cavitation. When the eccentricity is 5mm, the cavitation performance is improved. The effect of eccentricity on the radial force of impeller is reflected in the variation of force direction. Compared with other plans, the radial force is superior in transient cavitation under the eccentricity of 5mm.

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

scholarly journals Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1182
Author(s):  
Seung-Jun Kim ◽  
Yong Cho ◽  
Jin-Hyuk Kim
Keyword(s):  
Flow Rate ◽  
Draft Tube ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Air Injection ◽  
Low Flow ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Vortex Rope

Under low flow-rate conditions, a Francis turbine exhibits precession of a vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration of the turbine performance as manifested by torque and power output fluctuations. In order to suppress the rope with precession and a swirl component in the tube, the use of anti-swirl fins was investigated in a previous study. However, vortex rope generation still occurred near the cone of the tube. In this study, unsteady-state Reynolds-averaged Navier–Stokes analyses were conducted with a scale-adaptive simulation shear stress transport turbulence model. This model was used to observe the effects of the injection in the draft tube on the unsteady internal flow and pressure phenomena considering both active and passive suppression methods. The air injection affected the generation and suppression of the vortex rope and swirl component depending on the flow rate of the air. In addition, an injection level of 0.5%Q led to a reduction in the maximum unsteady pressure characteristics.

Sign in / Sign up

Export Citation Format

Share Document