Dynamic Stability Analysis of Cans in Reactor Coolant Pump Subjected to Axial Flow

2014 ◽  
Author(s):  
Wenbo Ning ◽  
Dezhong Wang
Keyword(s):  
Dynamic Stability ◽  
Cylindrical Shells ◽  
Axial Flow ◽  
Geometrical Parameters ◽  
Coolant Pump ◽  
Critical Flow Velocity ◽  
Reactor Coolant ◽  
Annular Gap ◽  
The Stability ◽  
Canned Motor

The stator and rotor cans in canned motor reactor coolant pump are assumed to be elastic coaxial cylindrical shells due to their particular geometric structures in present study. Thin shell structures such as cans are prone to buckling instabilities. Furthermore, a lot of accidents were caused by losing stability. The dynamic behavior of coaxial circular cylindrical shells subjected to axial fluid flow in the annular gap between two shells is investigated in this paper. The outer shell is stiffened by ring-ribs because of its instability easily. The shell is modeled based on Donnell’s shallow theory. The “smeared stiffeners” approach is used for ring-stiffeners. The fluid is assumed to be an incompressible ideal fluid and the potential flow theory is employed to describe shell-fluid interaction. Numerical analyses are conducted by means of energy variation to obtain the critical flow velocity of losing stability with aid of Hamilton principle. This study shows effects of geometrical parameters on stability of shells. The size and number of ring-stiffeners on dynamic stability are examined. It is found that stiffeners can vary modes instability and enhance the stability of shells. The flow velocities of losing stability with different boundary conductions can be calculated and compared. The results show clamped shells are more stable than simply supported shells. The results presented are in reasonable agreement with those available in the literature.

Numerical and Experimental Research on the Fluid-Induced Forces of Clearance Flow in Canned Motor Reactor Coolant Pump

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Rui Xu ◽  
Yun Long ◽  
Yaoyu Hu ◽  
Junlian Yin ◽  
Dezhong Wang
Keyword(s):  
Large Mass ◽  
Stiffness Coefficient ◽  
Pressurized Water ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Various Boundary Conditions ◽  
Clearance Flow ◽  
Mass Coefficient ◽  
Cfd Method ◽  
Canned Motor

Reactor coolant pump (RCP) is one of the most important equipment of the coolant loop in a pressurized water reactor system. Its safety relies on the characteristics of the rotordynamic system. For a canned motor RCP, the liquid coolant fills up the clearance between the metal shields of the rotor and stator inside the canned motor, forming a long clearance flow. The fluid-induced forces of the clearance flow in canned motor RCP and their effects on the rotordynamic characteristics of the pump are numerically and experimentally analyzed in this work. A transient computational fluid dynamics (CFD) method has been used to investigate the fluid-induced force of the clearance. A vertical experiment rig has also been established for the purpose of measuring the fluid-induced forces. Fluid-induced forces of clearance flow with various whirl frequencies and various boundary conditions are obtained through the CFD method and the experiment. Results show that clearance flow brings large mass coefficient into the rotordynamic system and the direct stiffness coefficient is negative under the normal operating condition. The rotordynamic stability of canned motor RCP does not deteriorate despite the existence of significant cross-coupled stiffness coefficient from the fluid-induced forces of the clearance flow.

scholarly journals Effect of Suction and Discharge Conditions on the Unsteady Flow Phenomena of Axial-Flow Reactor Coolant Pump

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1592
Author(s):  
Xin Chen ◽  
Shiyang Li ◽  
Dazhuan Wu ◽  
Shuai Yang ◽  
Peng Wu
Keyword(s):  
Unsteady Flow ◽  
Pressure Pulsation ◽  
Flow Reactor ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Uniform Flow ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Flow Phenomena ◽  
Rotating Impeller

In order to study the effects of the suction and discharge conditions on the hydraulic performance and unsteady flow phenomena of an axial-flow reactor coolant pump (RCP), three RCP models with different suction and discharge configurations are analyzed by computational fluid dynamics (CFD) method. The CFD results are validated by experimental data. The hydraulic performance of the three RCP models shows little difference. However, the unsteady flow phenomena of RCP are significantly affected by the variation of suction and discharge conditions. Compared with that of Model E-S (baseline, elbow-single nozzle), the pressure pulsation in rotating frame of Model S-S (straight pipe-single nozzle) and Model E-D (elbow-double nozzles) is weakened in different degrees and forms, due to the more uniform flow fields upstream and downstream of the impeller, respectively. It indicates that the generalized rotor-stator interaction (RSI) actually exists between the rotating impeller and all stationary components causing the circumferentially non-uniform flow. Furthermore, improving the circumferential uniformity of the flow upstream and downstream of impeller (suction and discharge flow) also contributes to reducing the radial dynamic fluid force acting on the impeller. Compared with those of Model E-S, the dynamic FX and FY of Model S-S are severely weakened, and those of Model E-D also gain a minor amplitude decrease at fBPF. In contrast, the general pressure pulsation in fixed frame is mainly related to the rotating impeller and barely affected by the suction and discharge conditions.

Experimental Research on the Fluid Induced Forces of Clearance Flow in Canned Motor Reactor Coolant Pump

2018 ◽  
Author(s):  
Rui Xu ◽  
Yaoyu Hu ◽  
Yun Long ◽  
Junlian Yin ◽  
Dezhong Wang
Keyword(s):  
Large Mass ◽  
Stiffness Coefficient ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Coolant Pump ◽  
Reactor Coolant ◽  
Various Boundary Conditions ◽  
Clearance Flow ◽  
Mass Coefficient ◽  
Canned Motor

Reactor coolant pump is one of the key equipment of the coolant loop in a pressurized water reactor system. Its safety relies on the characteristics of the rotordynamic system. For a canned motor reactor coolant pump, the liquid coolant fills up the clearance between the metal shields of the rotor and stator inside the canned motor, forming a clearance flow. The fluid induced forces of the clearance flow in canned motor reactor coolant pump and their effects on the rotordynamic characteristics of the pump are experimentally analyzed in this work. A vertical experiment rig has been established for the purpose of measuring the fluid induced forces of the clearance. Fluid induced forces of clearance flow with various whirl frequencies and various boundary conditions are obtained through the experiment. Results show that clearance flow brings large mass coefficient into the rotordynamic system and the direct stiffness coefficient is negative under the normal operating condition. The rotordynamic stability of canned motor reactor coolant pump does not deteriorate despite the existence of significant cross-coupled stiffness coefficient from the fluid induced forces of the clearance flow.

An Experimental Investigation of the Stability of Spiral Vortex Flow

1979 ◽  
Vol 21 (6) ◽  
pp. 397-402 ◽  
Author(s):  
M. M. Sorour ◽  
J. E. R. Coney
Keyword(s):  
Vortex Flow ◽  
Outer Cylinder ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Taylor Vortex ◽  
Vortex Cell ◽  
Annular Gap ◽  
Spiral Vortex ◽  
Axial Pressure Gradient ◽  
The Stability

The hydrodynamic stability of the flow in an annular gap, formed by a stationary outer cylinder and a rotatable inner cylinder, through which an axial flow of air can be imposed, is studied experimentally. Two annulus radius ratios of 0.8 and 0.955 are considered, representing wide- and narrow-gap conditions, respectively. It is shown that, when a large, axial pressure gradient is superimposed on the tangential flow induced by the rotation of the inner cylinder, the characteristics of the flow at criticality change significantly from those at zero and low axial flows, the axial length and width of the resultant spiral vortex departing greatly from the known dimensions of a Taylor vortex cell at zero axial flow. Also, the drift velocity of the spiral vortex is found to vary with the axial flow. Axial Reynolds numbers, Rea, of up to 700 are considered.

Non-Linear Fluid-Structure Interaction in Cylindrical Shells

2002 ◽  
Author(s):  
M. H. Toorani ◽  
A. A. Lakis
Keyword(s):  
Natural Frequencies ◽  
Cylindrical Shells ◽  
Axial Flow ◽  
Present Theory ◽  
Nuclear Plant ◽  
Nuclear Industry ◽  
Linear Potential ◽  
Critical Flow Velocity ◽  
Fluid Structure ◽  
Non Linear

Nuclear plant reliability depends directly on its component performance. The higher heat transfer performance of nuclear plant components often requires higher flow velocities through the shell and tube heat exchangers. So, these cylindrical structures are subjected to either axial or cross flow, while the excessive flow-induced vibrations, (which are a major cause of machinery downtime; fatigue failure and high noise), limit the performance of these structures. On the other hand, these shell components often experience large amplitude vibrations that are greater than the shell thickness. Therefore, the evaluation of complex vibrational behavior of these structures is highly desirable in the nuclear industry. A semi-analytical approach has been developed in the present theory to predict the geometrical non-linearity influence on the natural frequencies of anisotropic cylindrical shells conveying axial flow. Particular important in this study is to obtain the natural frequencies of the coupled system of the fluid-structure, taking into account the geometrical non-linearity of the structure, and also estimating the critical flow velocity at which the structure loses its stability. The displacement functions, mass and stiffness matrices, linear and non-linear ones, of the structure are obtained by exact analytical integration over a hybrid element developed in this work. Linear potential flow theory is applied to describe the fluid effect that leads to the inertial, centrifugal and Coriolis forces. Numerical results are given and compared with those of experiment and other theories to demonstrate the practical application of the present method.

The Effect of Temperature Gradient on the Stability of Flow between Vertical, Concentric, Rotating Cylinders

1979 ◽  
Vol 21 (6) ◽  
pp. 403-409 ◽  
Author(s):  
M. M. Sorour ◽  
J. E. R. Coney
Keyword(s):  
Temperature Gradient ◽  
Velocity Ratio ◽  
Axial Flow ◽  
Wave Number ◽  
Taylor Vortex ◽  
Effect Of Temperature ◽  
Neutral Stability ◽  
Radial Temperature ◽  
Annular Gap ◽  
The Stability

The effect of a radial temperature gradient on the hydrodynamic stability in the annular gap formed by two, vertical, concentric cylinders, the inner being rotatable and the outer both stationary and isothermally heated, was studied for the cases of zero and imposed axial fluid flow in the annular gap. For zero axial flow, it was found that the temperature gradient destabilizes the flow while not affecting the form of the secondary flow, viz. the classic Taylor vortex. For imposed axial flow, the point of neutral stability was modified only when natural convection was strong enough to affect the parabolic velocity profile associated with that flow; the extent of this modification was shown to depend on the direction of the axial flow. Also, the longitudinal temperature gradients within the gap were found to influence the axial wave number and the drift-velocity ratio.

Modeling and Analysis of Canned Motor of the Nuclear Reactor Coolant Pump

2013 ◽  
Vol 328 ◽  
pp. 955-959
Author(s):  
Yu Shi Wang ◽  
Zhen Qiang Yao ◽  
Hong Shen ◽  
Ya Bo Xue ◽  
De Cheng
Keyword(s):  
Electromagnetic Field ◽  
Nuclear Reactor ◽  
Magnetic Flux Density ◽  
Two Dimensional ◽  
Coolant Pump ◽  
Modeling And Analysis ◽  
Reactor Coolant ◽  
Transient Electromagnetic ◽  
Flux Density Distribution ◽  
Canned Motor

This paper presents three important electromagnetic parameters design principles in modeling a large canned motor such as the canned motor inside the nuclear reactor coolant pump. The performances of the canned motor within the nuclear reactor coolant pump are also analyzed by establishing the two-dimensional transient electromagnetic field model. The simulation result of magnetic flux density distribution of canned motor is very close to practical situation. Simultaneously the efficiency, power factor and break-down torque of canned motor are analyzed through two-dimensional electromagnetic field finite element method.

Stability of Rotating Coaxial Cylindrical Shells Interacting with a Flowing and Rotating Fluid

2015 ◽  
Vol 15 (05) ◽  
pp. 1450071 ◽  
Author(s):  
Sergey A. Bochkarev ◽  
Valery P. Matveenko
Keyword(s):  
Compressible Fluid ◽  
Cylindrical Shells ◽  
Tangential Velocity ◽  
Fluid Flows ◽  
The Finite Element Method ◽  
Annular Gap ◽  
Classical Shell Theory ◽  
The Stability ◽  
Compressible Fluid Flows ◽  
Geometrical Dimensions

This paper is concerned with the numerical investigation of hydroelastic stability of stationary or rotating coaxial cylindrical shells, interacting with compressible fluid flows having the axial and tangential velocity components. The behavior of a flowing and rotating compressible fluid is considered in the framework of the potential theory. Elastic shells are described using the model of the classical shell theory. Numerical implementation was accomplished based on the semi-analytical variant of the finite element method. The paper presents the results of numerical experiments on the stability of shells interacting with different flow patterns for a variety of boundary conditions, geometrical dimensions, width of the annular gap between the outer and inner shell under the constraint of the outer shell rigidity. It has been shown that the elasticity of the outer shells has the greatest effect on the dynamic behavior of coaxial shells interacting with fluid flows having different combinations of velocity components.

Flutter of a Rectangular Cantilevered Plate

2006 ◽  
Author(s):  
Christophe Eloy ◽  
Claire Souilliez ◽  
Lionel Schouveiler
Keyword(s):  
Fourier Transforms ◽  
Flexural Rigidity ◽  
Fluid Pressure ◽  
Axial Flow ◽  
Three Dimensions ◽  
Fluid Viscosity ◽  
Mass Ratio ◽  
Critical Flow Velocity ◽  
Plate Aspect Ratio ◽  
The Stability

We address theoretically the stability of a cantilevered rectangular plate in an uniform and incompressible axial flow. We assume that the fluid viscosity and the plate viscoelastic damping are negligible. In this limit, a flutter instability arises from a competition between the destabilising fluid pressure and the stabilising flexural rigidity of the plate. The flutter modes are assumed to be two-dimensional but the potential flow is calculated in three dimensions in the asymptotic limit of large plate span. Using a Galerkin method and Fourier transforms, we are able to predict the flutter modes, their frequencies and growth rates. The critical flow velocity is calculated as a function of the mass ratio and the plate aspect ratio. We demonstrate a new result: a plate of finite span is more stable than a plate of infinite span.

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