• 한국초전도ㆍ저온공학회논문지
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• 제19권4호
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• pp.45-50
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• 2017

This paper presents a conceptual design and analysis for a 1-kW-class high-temperature superconducting rotating machine (HTSRM) rotor. The designed prototype is a small-scale integration system of a HTSRM and a HTS contactless rotary excitation device (CRED). Technically, CRED and HTSRM are connected in the same shaft, and it effectively charges the HTS coils of the rotor field winding by pumping fluxes via a non-contact method. HTS coils in rotor pole body and toroidal HTS wire in CRED rotor are cooled and operated by liquid nitrogen in cryogen tank located in inner-most of rotor. Therefore, it is crucial to securely maintain the thermal stability of cryogenic environment inside rotor. Especially, we critically consider not only on mechanical characteristics of the rotor but also on cryogenic thermal characteristics. In this paper, we conduct two main tasks covering optimizing a conceptual design and performing operational characteristics. First, rotor parameters are conceptually designed by analytical design codes. These parameters consider to mechanical and thermal performances such as mechanical strength, mechanical rigidity, and thermal heat losses of the rotor. Second, mechanical and thermal characteristics of rotor for 1-kW-class HTSRM are analyzed to verify the feasible operation conditions. Hence, three-dimensional finite element analysis (3D-FEA) method is used to perform these analyses in ANSYS-Workbench platform.

• Journal of Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.750-757
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• 2005

The objective of this study is an understanding of the effect of inlet flow angle on the output power performance of a Francis hydraulic turbine, An optimum induced angle at the inlet of the turbine is one of the most important design parameters to have the best performance of the turbine at a given operating condition, In general. rotating speed of the turbine is varied with the change of water mass flowrate in a volute, The induced angle of the inlet water should be properly adjusted to the operating condition to have maximum energy conversion efficiency of the turbine, In this study. a numerical simulation was conducted to have detail understanding of the flow phenomenon in the flow path and output power of the model Francis turbine. The indicated power produced by the model turbine at a given operating condition was found numerically and compared to the brake power of the turbine measured by experiment at KIER. From comparison of two results, turbine efficiency or energy conversion efficiency of the model turbine was estimated. From the study, it was found that the rotating power of the turbine linearly increased with the rotating speed. It means that the higher volume flow rate supplied. the bigger torque on the turbine shaft generated. The maximum brake efficiency of the turbine is around 46$\%$ at 35 degree of induced angle. The difference between numerical and experimental output of the model turbine is defined as mechanical efficiency. The maximum mechanical efficiency of the turbine is around 93$\%$ at 25$\∼$30 degree of induced angle.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.788-792
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• 2003

Rotating machines are widely used in industrial world and especially motor and generator take up much part of it. As for this kind of motor and generator, electrical loss due to eddy current is the very important factor and that is also a primary factor causes heat generation. To solve this kind of problem like the above. insulated laminating silicon steel sheet is used to prevent eddy current effect. Laminated rotor is widely used as rotating shaft of motor and generator. Due to that, electrical loss and heat problem can be solved but designer meets another problem. In general. most of the motor and generator can be normally operated under 3,600 rpm because they are designed to have the first critical speed more than that speed. But nowadays, they should be operated more than the first critical speed as usual with the trend of high speed, large scale and high precision in industrial world. The critical speed can be determined from the inertia and stillness for the rotor and bearing of rotating systems. The laminated rotor stiffness can be hardly determined because it can be derived a lot factors for instance rotor material and shape, lamination material and shape, insulation material. lamination force and so on. In this paper, the change of the natural frequency of the motor was examined with the change of the lamination force as an experimental method and design criteria will be presented for motor & generator designer, who can apply the result of numerical analysis with equivalent diameter scheme with ease.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.197-202
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• 1999

A mechanical face seal is a tribe-element intended to control the leakage of working fluid at the interface of a rotating shaft and its housing. The leakage of working fluid decreases as the seal surfaces get closer each other. But a very small seal clearance results in a drastic reduction of seal life because of high wear and heat generation. Therefore, in the design of mechanical face seals the compromise between low leakage and acceptable life is important and presents a difficult design problem. And the gap geometry of seal clearance affects seal performance very much and becomes an important design variable. In this study the Reynolds equation for the sealing dam of mechanical face seals is numerically analyzed using the Galerkin Finite Element Method, which can be readily applied to various seal geometries. The film pressures of the sealing dam are analyzed, including the effects of the seal face coning and tilt. Then, opening forces, restoring moments, leakages, and dynamic coefficients are calculated.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.41-46
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• 2003

In this paper, two different methods are developed to be used for the design of noncontact dry gas seal which is used to prevent gas leakage of high speed rotating shaft-housing machineries. First method is using FEA to compute the deformation of seal face and the other is using Influence Coefficient Method in order to save computation of FEA. In both cases, heat load and mechanical loads are applied such as heat generation, bulk temperature and nodal force, bulk pressure, centrifugal force, respectively. ICM method is verified correct and effective and both methods give reliable and useful deformation results for the design of mechanical seals.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.749-754
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• 2004

Up to now, non-explosive demining system adaptable to a mobile robot has been developed. This system has much smaller platform and consists of non-explosive mechanism. Brief experiment indoors showed thai developed demining system can remove landmines well. But, out of doors, some problems are detected i.e. Inclination of overall system causes a suspension of rake rotation. In this research, a study on performance improvement of developed non-explosive demining system is mainly discussed. To compensate the inclination of the system, mechanical sensor composed of shaft and spring is used. This sensor gives a signal to a leadscrew motor and controls a rotating direction. From an experiment, it is confirmed that the mechanical sensor as stated is a good solution of the inclination of the system.

• 한국소음진동공학회논문집
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• 제13권11호
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• pp.852-859
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• 2003

In order to meet the growing demands for higher storage density as well as lower noise level, the spindles in hard disk drives are to be supported by hydrodynamic bearings in place of conventional ball-type ones. However, the existing models are inappropriate to apply to accurate prediction of vibration characteristics because the HDD spindle tends to take quite a complex shape to secure its performance and cost-effectiveness. In this context, this paper treats analysis of free and forced vibrations of such-designed HDD spindles based on more sophisticated models and validations via experiments. Remarkably, to this end all the components in the system are modeled as elastic adopting the finite element method.

• Tribology and Lubricants
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• 제12권4호
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• pp.43-51
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• 1996

Rapid increase of refrigeration & air-conditioning system (r & a system) in modem industries brings attention to the urgency of research & development as a core technology in the area. And it is required to the compatibility problem of r & a system to alternative refrigerant for the protection of environment. Then, it is requested to study the lubrication characteristics of refrigerant compressor which is the core technology in the r & a system. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressor. Therefore, theoretical investigation of the lubrication characteristics of rotary compressor for r & a system is studied. The Runge-Kutta method is used for the analysis of the behavior of rolling piston in the rotary compressor. The results show that the rotating speed of shaft and the discharge pressure have an important effect upon the angular velocity of the rolling piston. This results give important basic data for the further lubrication analysis and design of the rotary compressor.

• 대한기계학회논문집
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• 제7권2호
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• pp.186-192
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• 1983

The purpose of this study is to determine the general frequency expression for a rotating shaft of uniform cross section, supported by two bearings, and carrying flywheel at the free end. The bearing spacing and the ratio of the weight of flywheel to the total distributed weight are used as parameters. The data have thus been reduced to dimensionless form so that the results are generally applicable for this type of rotor. Frequencies for the first three modes of vibration are determined. Experimental investigation with rotor/flywheel model confirmed the critical speed frequencies lie between analytical models with simply supported-simply supported boundary conditions and spring supported-spring supported boundary conditions.

• 한국정밀공학회지
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• 제12권3호
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• pp.23-31
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• 1995

The sending characteristics of the non-contact type displacement transducers can affect the performances of the magnetic bearing systems when they support the rotating shaft. The probe type displacement sensor detects not only the displacement of the rotor at the sensing position but also the surface irregularitis of the rotor such as surface roughnessand roundness errors. If there exist such measuring errors, the magnetic bearing can not apply proper force against the rotor displacements for the detected signal is the input to the magnetic bearing controllers. The cylindrical shape capacitive transducer can detect the rotor displacement by the integral sum of the charges which are formed between the sensor plates and rotor so that it can reduce the detecting errors induced by the surface irregularities of the rotor. By theore- tical analysis, we compared the sensing characteristics of the cylindrical shape capacitive transducers for the rotors that have some sinusoidal irregularities with that of the ideal probe type displacement transducers.