Numerical Simulation of the Transient Flow in a Centrifugal Pump during Regulating Period

2011 ◽  
Vol 268-270 ◽  
pp. 1407-1410
Author(s):  
Yue Tang ◽  
Er Hui Liu ◽  
Ling Di Tang ◽  
Wang Hui
Keyword(s):  
Fluid Flow ◽  
Centrifugal Pump ◽  
Moving Boundary ◽  
Transient Flow ◽  
Pressure Fluctuations ◽  
Angular Acceleration ◽  
Internal Flow ◽  
Dynamic Mesh ◽  
Hydrodynamic Performance ◽  
State Process

Centrifugal pump performance has transient effect obviously during rapid changing period and the pump hydrodynamic performance of transient is different from steady-state process. In order to research the speed regulation characteristics and the inner flow mechanism of the centrifugal pump, numerical method of solving the unsteady fluid flow around the accelerating blade was established. The dynamical changes of the pressure and velocity were simulated by Fluent6.2, using standard k-epsilon turbulence model, PISO algorithm. The dynamic mesh technology and UDF were used to deal with the moving boundary caused by changing speed. Simulation results shown that faster angular acceleration made larger pressure fluctuations. Different regulated time had different influence in the system transient characteristics. And the evolution of the internal flow rate present strong transient performance in the regulating process. The study confirmed the feasibility of dynamic mesh method in solving the transient fluid flow during pump regulating period.

Compendious Review on “Internal Flow Physics and Minimization of Flow Instabilities Through Design Modifications in a Centrifugal Pump”

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Neeta A. Mandhare ◽  
K. Karunamurthy ◽  
Saleel Ismail
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuations ◽  
Internal Flow ◽  
Boundary Layer Separation ◽  
Industrial Applications ◽  
Centrifugal Pumps ◽  
Pump Impeller ◽  
Design Modification ◽  
Flow Physics ◽  
And Performance

Centrifugal pumps are one of the significant consumers of electricity and are one of the most commonly encountered rotodynamic machines in domestic and industrial applications. Centrifugal pumps operating at off-design conditions are often subject to different periodic flow randomness, which in turn hampers functionality and performance of the pump. These limitations can be overcome by modification in the conventional design of different components of a centrifugal pump, which can assuage flow randomness and instabilities, reconstitute flow pattern and minimize hydraulic flow losses. In this article, flow vulnerabilities like pressure and flow inconsistency, recirculation, boundary layer separation, adverse rotor–stator interaction, and the effects on operation and performance of a centrifugal pump are reviewed. This article also aims to review design modification attempts made by different researchers such as impeller trimming, rounding, geometry modification of different components, providing microgrooves on the impeller and others. Based on the findings of this study, it is concluded that some design modifications of the impeller, diffuser, and casing result in improvement of functionality, efficiency, and reduction in pressure fluctuations, flow recirculation, and vibrations. Design modifications should improve the performance without hampering functionality and useful operational range of the pump. Considerable research is still necessary to continue understanding and correlating flow physics and design modifications for the pump impeller, diffuser, and casing.

Numerical Study on Transient Dynamics in a Centrifugal Pump Considering Clearance Flow

2018 ◽  
Author(s):  
Chen-Xing Jiang ◽  
Xi Wang ◽  
Na-Xin Kang ◽  
Xiang-Yuan Zhang ◽  
Zhi-Jun Shuai ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Transient Flow ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Structure Design ◽  
Hydraulic Loss ◽  
Flow State ◽  
Axial Forces ◽  
Clearance Flow

This paper investigates the transient flow characteristics and the forces on the impeller in a single-stage centrifugal pump considering the clearance flow. The finite volume method is employed to simulate the dynamics process. First, Numerical simulation is carried out in a commercial code CFX. The external performance characteristics, internal flow structure and pressure fluctuation in the two different models, with clearance and without clearance, are compared. It is found that the existence of the clearance flow can generate more vortex and hydraulic loss, which makes the flow state more complicated. Besides, the transient radial and axial forces on the impeller are analyzed. And an optimized model with modified chamber flow field is proposed, which can provide a theoretical foundation on the structure design of the centrifugal pump.

Numerical Simulation of the Transient Flow in a Centrifugal Pump During Starting Period

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Zhifeng Li ◽  
Dazhuan Wu ◽  
Leqin Wang ◽  
Bin Huang
Keyword(s):  
Centrifugal Pump ◽  
Transient Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Published Data ◽  
Pipe System ◽  
Mesh Method ◽  
Slip Region ◽  
Transient Operations ◽  
Dynamic Slip

Computational fluid dynamics were used to study the three-dimensional unsteady incompressible viscous flows in a centrifugal pump during rapid starting period (≈0.12 s). The rotational speed variation of the field around the impeller was realized by a dynamic slip region method, which combines the dynamic mesh method with nonconformal grid boundaries. In order to avoid introducing errors brought by the externally specified unsteady inlet and outlet boundary conditions, a physical model composed of a pipe system and pump was developed for numerical self-coupling computation. The proposed method makes the computation processes more close to the real conditions. Relations between the instantaneous flow evolutions and the corresponding transient flow-rate, head, efficiency and power were analyzed. Relative velocity comparisons between the transient and the corresponding quasisteady results were discussed. Observations of the formations and evolutions of the primary vortices filled between the startup blades illustrate the features of the transient internal flow. The computational transient performances qualitatively agree with published data, indicating that the present method is capable of solving unsteady flow in a centrifugal pump under transient operations.

Numerical and Experimental Analysis of Flow Phenomena in a Centrifugal Pump Operating Under Low Flow Rates

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Yanxia Fu ◽  
Jianping Yuan ◽  
Shouqi Yuan ◽  
Giovanni Pace ◽  
Luca d'Agostino ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Internal Flow ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Low Flow ◽  
Flow Rates ◽  
Wide Range

The characteristics of flow instabilities as well as the cavitation phenomenon in a centrifugal pump operating at low flow rates were studied by experimental and numerical means, respectively. Specially, a three-dimensional (3D) numerical model of cavitation was applied to simulate the internal flow through the pump and suitably long portions of the inlet and outlet ducts. As expected, cavitation proved to occur over a wide range of low flow rates, producing a characteristic creeping shape of the head-drop curve and developing in the form of nonaxisymmetric cavities. As expected, the occurrence of these cavities, attached to the blade suction sides, was found to depend on the pump's flow coefficient and cavitation number. The experiments focused on the flow visualization of the internal flow patterns by means of high-speed digital movies and in the analysis of the inlet pressure pulsations near the impeller eye by means of fast response pressure transducers. The experimental results showed that the unsteady behavior of the internal flow in the centrifugal pump operating at low flow rates has the characteristics of a peculiar low-frequency oscillation. Meanwhile, under certain conditions, the low-frequency pressure fluctuations were closely correlated to the flow instabilities induced by the occurrence of cavitation phenomena at low flow rates. Finally, the hydraulic performances of the centrifugal pump predicted by numerical simulations were in good agreement with the corresponding experimental data.

Effects of Splitter Blades on the Unsteady Flow of a Centrifugal Pump

2012 ◽  
Author(s):  
Liting Ye ◽  
Shouqi Yuan ◽  
Jinfeng Zhang ◽  
Ye Yuan
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Simulations ◽  
Centrifugal Pump ◽  
Pressure Fluctuations ◽  
Internal Flow ◽  
Suction Side ◽  
Boundary Function ◽  
Wake Flow ◽  
Design Parameters

Numerical simulations and performance tests were conducted to analyze the effects of splitter blades on the performance and whole unsteady flow field of a centrifugal pump. The studied pump is a single stage pump with a shrouded impeller (diameter = 160mm, 4 blades, specific speed = 47). Based on the original impeller, we designed 5 impellers with different splitter blades parameters. All the numerical simulations were carried out by using the commercial software ANSYS CFX 12.1 based on standard k-ε turbulence model and standard boundary function. The results showed that, the head of the impellers with splitter blades was approximately 2%∼12% higher than that without splitter blades. When adding splitter blades, the pressure fluctuations at the impeller inlet, volute outlet and the interface of impeller and volute are reduced, this can improve the “jet-wake” flow structure. Different design parameters of splitter blades have a certain effect on the pressure fluctuations at the interface of impeller and volute. When the splitter blades deviated 5° to the suction side of the long blade and the splitter blade inlet diameter is 106 mm, the head is highest and the pressure fluctuations are lowest. The work will provide a basis for the further study on the internal flow field, reducing vibration and noise of a centrifugal pump.

Axisymmetric flow near the critical point on the moving boundary

2010 ◽  
Vol 7 ◽  
pp. 182-190
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh. Nasibullaeva
Keyword(s):  
Fluid Flow ◽  
Finite Difference ◽  
Boundary Conditions ◽  
Numerical Solution ◽  
Axial Velocity ◽  
Moving Boundary ◽  
Axisymmetric Flow ◽  
Boundary Motion ◽  
Newton Raphson ◽  
Raphson Method

In this paper the investigation of the axisymmetric flow of a liquid with a boundary perpendicular to the flow is considered. Analytical equations are derived for the radial and axial velocity and pressure components of fluid flow in a pipe of finite length with a movable right boundary, and boundary conditions on the moving boundary are also defined. A numerical solution of the problem on a finite-difference grid by the iterative Newton-Raphson method for various velocities of the boundary motion is obtained.

Numerical Investigation of the Transient Flow and Frequency Characteristic in a Centrifugal Pump with Splitter Blades

2020 ◽  
Author(s):  
Guidong Li ◽  
Jinfeng Zhang ◽  
Jieyun Mao ◽  
Shouqi Yuan ◽  
Jing Jia
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Pump ◽  
Frequency Characteristic ◽  
Transient Flow

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 The effect of solid particle size and concentrations on internal flow and external characteristics of the dense fine particles solid–liquid two-phase centrifugal pump under low flow condition

AIP Advances ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 085309
Author(s):  
Yanping Wang ◽  
Weiqin Li ◽  
Tielin He ◽  
Chuanfeng Han ◽  
Zuchao Zhu ◽  
...  
Keyword(s):  
Particle Size ◽  
Centrifugal Pump ◽  
Solid Particle ◽  
Flow Condition ◽  
Fine Particles ◽  
Internal Flow ◽  
Low Flow ◽  
Two Phase ◽  
Solid Liquid ◽  
External Characteristics

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.

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