• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.1-8
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• 2013

Surface permanent magnet-type vernier motors with three magnet array-type rotors (parallel magnetized type, repulsion type, and Halbach type) are compared based on the pull-out torque. It was clarified that increasing the rotor radius increases the pull-out torque at a fixed three-phase alternating voltage. The mechanism for the pull-out torque increase on each magnet array type was different, when the effects of the increase were analyzed based on an induced electromotive force and a synchronous reactance. As a result, the design of the Halbach-type rotor was found to be especially effective for achieving high pull-out torque, because this array type achieves a large induced electromotive force $E_0$ and a small synchronous reactance $x_s$.

• 한국정밀공학회지
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• 제19권4호
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• pp.140-146
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• 2002

High speed rotating machines can be very sensitive to rotating mass unbalance that is a major source of harmful vibration for many types of rotating machinery. So, the balancing procedure is needed for all high-speed rotating system. To save the time and cost of off-line balancing, many researchers have developed the on-line balancing devices and methods. In this paper, an active balancing device, which is an electro-magnetic type, is developed and the active balancing algorithm using influence coefficient method is also proposed. The active balancing experiment for flexible rotors during operation is performed by an active balancing device. As a result, controlled unbalance responses are below the vibration limit at all rotating speed ranges with critical speed.

• 한국안전학회지
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• 제10권1호
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• pp.3-8
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• 1995

The anemometer measurements were obtained from stationary hot-film probe mounted between the forward and rear rotors of a model CRP which rotated the forward and different directions. Data collection was done at several locations between rotors. To establish rotor-rotor interaction flow mechanism that contributes noise increasement of the CRP, methods of simple and the double condition-at sampling have been developed. The former uses to find similarity of the wake the later fixes the forward rotor position in time or space and permits averaging the mean wake at any fixed rotor angular location. The variation of the forward wake Is strongly depending upon the rear rotor location.

• Journal of Advanced Marine Engineering and Technology
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• 제30권8호
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• pp.843-852
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• 2006

Vibration/noise analysis as well as strength of planetary gear train are considered in order to develop a transmission for a high-speed ship. The vibration model of a gear pair is developed with considering the elastic deformation of the active teeth and the body to be a rigid. Excitation forces of the transmission system are considered as the mass unbalance of the rotors. misalignment and a function of gear transmission error which comes from the modified tooth surface. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors. misalignment and the transmitted errors of the gearing are considered shows that, at the operating speed, there are not the critical speed.

• 한국정밀공학회지
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• 제25권11호
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• pp.73-82
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• 2008

A dynamic model of reducer for generating facility of electric pourer having bevel gear pair and planetary gear train is developed by lumped method. The model accounts for the shaft and bearing flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Vibration/noise analysis as well as strength of bevel gear pair and planetary gear train are considered. Exciting forces of high reducer for generating facility of electric power areconsidered as the mass unbalance of the rotors, misalignment and a function of gear transmission error. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors, misalignment and the transmitted errors of the gearing are considered, shows that, at the operating speed, there are not critical speed.

• 동력기계공학회지
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• 제9권1호
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• pp.23-29
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• 2005

Numerical analysis of three-dimensional viscous flow-fields in the turbine rotor passages was carried out to investigate flow physics including the interaction between secondary vortices, tip leakage vortex, and the rotor wake. The blade tip geometry was accurately modeled adopting the embedded H grid system. An explicit four-stage Runge-Kutta scheme was used for the time integration of both the mean flow and turbulence equations. The computational results for the entire turbine rotor flows, particularly the tip clearance flow and the secondary flows, were interpreted and compared with the experimental data from the Penn State turbine stage. The predictions for major features of the flow field have been found to be in good agreement with the experimental data.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.889-898
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• 2002

This part of ISO 1940 gives recommendations for determining unbalance and for specifying related quality requirements of rigid rotors; it specifies a) a representation of unbalance in one or two planes; b) methods for determining permissible residual unbalance; c) methods for allocating it to the correction planes; d) methods for identifying he residual unbalance state of a rotor by measurement; e) a summary of errors associated with the residual unbalance identification. This part of ISO 1940 is also intended to facilitate the relations between manufacturer and user of machines. Detailed consideration of errors associated with the determination of residual unbalance is covered in the 2nd part of ISO 1940 (ISO 1940-2 will deal with these errors).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.306-310
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• 2014

The purpose of this study is the stability evaluation of a vacuum pump through modal test and rotor dynamics. Eigenvalue was solved by the finite-element method(FEM) using 2D and 3D models, then the modal test result was compared with the FEM result. According to the comparison, the analysis result using the 2D was more accurate than the 3D model. Therefore, rotor dynamics was performed by the 2D model. Campbell diagram and root-locus maps, which were calculated by complex-eigenvalue analysis, were used to evaluate the stability of the rotors of the vacuum pump. And displacement solved by unbalance response analysis was compared with the minimum clearance between two rotors of the vacuum pump. Thus, the vacuum pump is assumed operated under steady state through the evaluation of the rotor dynamics.

• International Journal of Aeronautical and Space Sciences
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• 제5권1호
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• pp.39-45
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• 2004

The vibration characteristics of rotating machinery are directly related withits condition such as rotor types, thereby it should be acquired the information fromthe vibration signal so that operating conditions may be rationally decided.Accordingly, the study is to focus on developing the analysis for identifying theoperational feature of rotor systems. For this purpose the complex frequencyanalysis for identification, which utilizes the directionaI spectrum for effectiveidentification of rotor systems, is introduced. From this proposed method, theanalysis of dynamic model of the rotors is performed including the stabilitybehavior of the general rotor by Ftoquet theory. Through this process theexcitation methodology to identify the types of rotors is investigated and theeffective way to identification is also suggested.

• International Journal of Aeronautical and Space Sciences
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• 제6권1호
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• pp.89-96
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• 2005

Ducted fans have advantages in noise as well as operational safety aspects compared to conventional tail rotors and are used as an anti-torque system for various classes of helicopters. The final goal of this study is to develop a ducted fan anti-torque system which can replace conventional tail rotors of existing helicopters to achieve safety enhancement and low noise level. In this paper, a conceptual design process and the results are described. Initially, the design requirement and the design parameter characteristics are analysed, and then initial sizing and configuration design are performed. There are several configuration changes due to specific technical reasons in each case. Finally, the required power and the pitch link load are predicted as an initial estimation. The conceptual design technique for the ducted fan in this study can be easily applied to the design of other ducted fans such as the lift fan for unmanned aerial vehicle.