• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.56-63
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• 1997

Sealing of lubricant-air mixture in the high performance machining center is one of most the important characteristics to carry out enhanced lubrication. High speed spindle requires non-contact type of sealing mechanism. Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Effect of geometry and leakage path are evaluated according to variation of sealing geometry. Velocity, pressure, turbulence intensity of profile is calculated to find more efficient geometry and variables. This offers a methodological way of enhancement seal design for high speed spindle. The working fluid is regarded as two phases that are mixed flow of oil phase and air phase. It is more reasonable to simulate an oil jet or oil mist type high speed spindle lubrication. Turbulence and compressible flow model are used to evaluate a flow characteristic. This paper considers a design effect of sealing capability of non- contact type seals for high speed spindle and analyzes leakage characteristics to minimize a leakage 7 on the same sealing area.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1807-1811
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• 2008

In this paper, the meniscus formation/deformation processes and conduction characteristics of the needle-centered ceramic nozzle electrode as an effective electrohydrodynamic (EHD) flow driving mechanisms for de-ionized water and silicone oil have been investigated. Results showed that the applied high voltage affected significantly on the processes, such as the drop formation mode, the deformation mode, the dripping mode, the jet mode, and the atomization mode. There was the EHD atomization mode for the de-ionized water while it was not occurred for the silicone oil, which, however, might be due to the lower electric conductivity and dielectric property of the oil than that of the water.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.176-180
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• 1997

Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Flow is characterized into five categories according to its leakage path. Effect of geometry and leakage path are evaluated according to variation of sealing geometry. To simulate an oil jet or oil mist type high speed spindle lubrication, the working fluid is regarded as two phases that are mixed flow of oil phase and air phase. Both of the turbulence and the compressible flow model were introduced in CFD(Computational Fluid Dynamics) analysis. This offers a methodological way of enhancement seal design for high speed spindle.

• Tribology and Lubricants
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• v.11 no.5
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• pp.122-127
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• 1995

The heat generations of angular contact ball bearings are studied experimentally with numerical simulations. The temperature variations of inner and outer races and the temperature increase distributions are measured by using thermocouples for the spindle rotational speeds, preloads, viscosity of oils, and lubrication methods. The measured values from experiments are used to estimate the heat generation rates. The heat generation is focused mainly on the dominant sources which are robbings due to spin and gyro-moments of bearing balls, applied load and viscous friction. Oil-jet and oil-air lubrication methods are adopted using oils with different viscosities.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.147-153
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• 2014

The centrifugal oil purifier is used in an engine for lubrication and to remove impurities. The momentum needed for the rotation of the cylindrical chamber is obtained by jet injections. An impure particle in the oil is separated by the centrifugal forces moving to the inner wall of the rotating cylindrical chamber body. The dust particles are eliminated when the particles are absorbed onto the surface of the inner wall of the chamber body. The flow characteristics and the physical behaviors of particles in this centrifugal oil purifier were investigated numerically and the filtration efficiencies was evaluated. For calculations, a commercial code is used and the SST (Shear Stress Transport) turbulence model has been adopted. The MFR (Multi Frames of Reference) method is introduced to consider the rotating effect of the flows. Under various variables, such as particle size, particle density and rotating speed, the filtration efficiencies are evaluated. It has been verified that the filtration efficiency is increased with the increments in the particle size, the particle density and the rotating speed of the cylindrical chamber.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1616-1623
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• 2001

A basic experimental study has been carried out to find out the design parameters of fuel 2-staging atomizers in order to reduce nitrogen oxides(NOx) rate emitted from the steam boilers used the liquid fuel. The heavy fuel oil(B-Coil) and fuel 2-staging Y-jet twin-fluid atomizers were adopted in this study. The results of this paper were obtained from the real as well as the model scale atomizers. In the case of model atomizers test, NOx reduction rate was strongly dependent on the staged fuel rate, but it was weakly dependent on the injection hole arrangement and air swirl conditions. The real scale atomizers was designed and manufactured on the base of these test results, and those was mounted and operated in the real boiler generates 185 ton steam per an hour. The reduction rate of the model and real plant was reached 10∼30% of base NOx by atomizers. but dust was sharply increased in the low O$_2$combustion region of the real plant.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1571-1581
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• 1998

A flow visualization study was carried out for the branch pipe mixing flow in which a jet was issued normally to the fully developed pipe flow. An instantaneous laser tomographic method was used for cross flow Reynolds numbers based on the cross flow diameter D ranged $Re_{cf}=5.26{\times}10^3{\sim}1.13{\times}10^4$, diameter ratios d/D = 0.1 ~ 0.2 and velocity ratios R = 0.5 ~ 10. Oil mist with the size of about $10{\mu}m$ diameter was used for the scattering particle. The main purpose of this study was to reveal the physical mechanism and the structure of vortices formation with varying the velocity ratios and diameter ratios in the branch pipe flow. It was found that the physical mechanism and the structures of vortices formation were quite different depending on the velocity ratios. Particularly in the case of R < 1, the typical vortex shows single loop shape and that for the case of R > 1 depicts mushroom-like structure in the cross flow jet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1578-1584
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• 2002

Combustion stability is one of the most important factors that must be considered in burning of heavy fuel oil, especially low-grade oil. This paper describes the combustion characteristics of petrochemical process by- product in the combustion furnace of heavy fuel oil. Main experimental parameters were combustion load, excess 02, fuel preheating temperature and air/fuel ratio. The capacity of CRF(combustion research facility) used in this study was 1.0 ton/hr and the burner is steam jet type suitable far heavy oil combustion and manufactured by UNIGAS in Italy. The fuel used in this experiment were 0.5 B-C, petrochemical process by-product and 3 kinds of 0.5 B-C/process by-product mixtures. The combustion stability was monitored and exhaust gases such as CO, NOx, SOx and particulates were measured with the excess $O_2$ and combustion load. The main purpose of this study is to clarify whether process by-product can be used as a boiler fuel or not in consideration of flame stability and emission properties.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.221-226
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• 2002

This paper presents the thermal characteristics analysis of a high-speed HMC(horizontal machining center) with spindle speed of 30,000rpm and fried rate of 40m/min. The spindle speed is achieved by introducing angular contact ball bearings, oil-jet lubrication method, oil jacket cooling method, and so on. The spindle system is a motor-separated type composed of the main spindle and sub-spindle which are mechanically connected by the flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front to and rear bearings of the sub-spindle. The thermal analysis model of HMC is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution and heat flow under the various testing conditions related to spindle speed and feed rate.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.237-242
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• 2001

This paper presents the thermal characteristics analysis of a high-speed HMC spindle system with angular contact ball bearings, built-in motor, oil-jet lubrication method, oil jacket cooling method, and so on. The spindle system is composed of the main spindle and sub-spindle which are mechanically connected by a flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front and rear bearings of the sub-spindle. The thermal analysis model of spindle system is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution, heat flow and thermal deformation under the various testing conditions related to material of bearing ball, spindle speed and coolant temperature.