Research on the clearance flow between stator and rotor cans in canned motor RCP

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.

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

Volume 2: Plant Systems, Structures, Components, and Materials; Risk Assessments and Management ◽

10.1115/icone26-82296 ◽

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.

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Research on the flywheel clearance flow in canned motor RCP

Annals of Nuclear Energy ◽

10.1016/j.anucene.2020.107816 ◽

2021 ◽

Vol 150 ◽

pp. 107816

Author(s):

Rui Xu ◽

Yuchen Song ◽

Xiyao Gu ◽

Yujin Wang ◽

Dezhong Wang

Keyword(s):

Clearance Flow ◽

Canned Motor

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Lock-in phenomenon of tip clearance flow and its influence on aerodynamic damping under specified vibration on an axial transonic compressor rotor

Chinese Journal of Aeronautics ◽

10.1016/j.cja.2021.02.016 ◽

2021 ◽

Author(s):

Le Han ◽

Dasheng Wei ◽

Yanrong Wang ◽

Mingchang Fang

Keyword(s):

Tip Clearance ◽

Tip Clearance Flow ◽

Aerodynamic Damping ◽

Transonic Compressor ◽

Compressor Rotor ◽

Clearance Flow ◽

Lock In

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Effect of the Reynolds Number and Clearance Flow on the Aerodynamic Characteristics of a New Variable Inlet Guide Vane

Aerospace ◽

10.3390/aerospace8070172 ◽

2021 ◽

Vol 8 (7) ◽

pp. 172

Author(s):

Hengtao Shi

Keyword(s):

Reynolds Number ◽

Guide Vane ◽

Three Dimensional ◽

High Growth ◽

Aerodynamic Characteristics ◽

Inlet Guide Vane ◽

Separation Region ◽

Clearance Flow ◽

New Type ◽

Variable Inlet Guide Vane

Recently, a new type of low-loss variable inlet guide vane (VIGV) was proposed for improving a compressor’s performance under off-design conditions. To provide more information for applications, this work investigated the effect of the Reynolds number and clearance flow on the aerodynamic characteristics of this new type of VIGV. The performance and flow field of two representative airfoils with different chord Reynolds numbers were studied with the widely used commercial software ANSYS CFX after validation was completed. Calculations indicate that, with the decrease in the Reynolds number Rec, the airfoil loss coefficient ω and deviation δ first increase slightly and then entered a high growth rate in a low range of Rec. Afterwards, a detailed boundary-layer analysis was conducted to reveal the flow mechanism for the airfoil performance degradation with a low Reynolds number. For the design point, it is the appearance and extension of the separation region on the rear portion; for the maximum incidence point, it is the increase in the length and height of the separation region on the former portion. The three-dimensional VIGV research confirms the Reynolds number effect on airfoils. Furthermore, the clearance leakage flow forms a strong stream-wise vortex by injection into the mainflow, resulting in a high total-pressure loss and under-turning in the endwall region, which shows the potential benefits of seal treatment.

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Investigation of a Tip Clearance Cascade in a Water Analogy Rig

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3239883 ◽

1986 ◽

Vol 108 (1) ◽

pp. 38-46 ◽

Cited By ~ 11

Author(s):

J. A. H. Graham

Keyword(s):

Turbine Blades ◽

Flow Region ◽

Tip Clearance ◽

Turbine Engines ◽

Gas Turbine Engines ◽

Tip Clearance Flow ◽

Pressure Profiles ◽

Clearance Flow ◽

Hot Film ◽

Model Features

The tip clearance flow region of high-pressure axial turbine blades for small gas turbine engines has been investigated in a water flow cascade. The blade model features variable clearance and variable endwall speeds. The cascade is scaled for Reynolds number and sized to give velocities suitable for visualization. Pressure profiles were measured on one blade, and correlated with the visualization. Unloading is found to be a major feature of the pressure field at both tip and midspan, and is intimately connected with scraping effects and the behavior of the clearance vortex. Some initial hot-film velocity measurements are also presented.

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Endwall Blockage in Axial Compressors

Journal of Turbomachinery ◽

10.1115/1.2841344 ◽

1999 ◽

Vol 121 (3) ◽

pp. 499-509 ◽

Cited By ~ 97

Author(s):

S. A. Khalid ◽

A. S. Khalsa ◽

I. A. Waitz ◽

C. S. Tan ◽

E. M. Greitzer ◽

...

Keyword(s):

Tip Clearance ◽

Design Parameters ◽

Tip Clearance Flow ◽

Axial Compressors ◽

Clearance Flow ◽

Flow Features ◽

Physical Insight ◽

Level Loading ◽

Stagger Angle ◽

Insight Into

This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.

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