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박경택(K. T. Park),박태조(T. J. Park) 유공압건설기계학회 2008 드라이브·컨트롤 Vol.5 No.1
Various types of hydraulic shock absorbers are widely used in many fields because of its numerous advantages. However, in order to design adequate damping characteristics, accurate flow data near the orifices are required essentially. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is adopted to investigate the flow characteristics near orifices of a shock absorber. Static pressure and velocity vector distributions, fluid path lines are presented for compression/tension strokes and various piston speeds. In order to validate the result of analysis, the numerically obtained damping forces are compared with those of analytical estimations obtained by modified Bernoulli equation. The results reported herein will provide better understanding of the detailed flow fields within shock absorber, and the CFD analysis method proposed in this paper can be used in the design of other types of hydraulic shock absorber.
박경택(K. T. Park),신영재(Y. J. Shin),강병수(B. S. Kang) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
Recently the monitoring system of tool setup in high speed precision machining tool is required for manufacturing products that have highly complex and small shape, high precision and high function. It is very important to reduce time to setup tool in order to improve the machining precision and productivity and to protect the breakage of cutting tool as the shape of product is smaller and more complex. Generally, the combination of errors that geometrical clamping error of fixing tool at the spindle of machining center and the asynchronized error of driving mechanism causes that the run-out of tool reaches to 3∼20 times of the thickness of cutting chip. And also the run-out is occurred by the misalignment between axis of tool shank and axis of spindle and spindle bearing in high speed rotation. Generally, high speed machining is considered when the rotating speed is more than 8,000 rpm. At that time, the life time of tool is reduced to about 50% and the roughness of machining surface is worse as the run-out is increased to 10 micron. The life time of tool could be increased by making monitoring of tool-setting easy, quick and precise in high speed machining center. This means the consumption of tool is much more reduced. And also it reduces the manufacturing cost and increases the productivity by reducing the tool-setup time of operator. In this study, in order to establish the concept of tool-setting monitoring the measuring method of the geometrical error of tool system is studied when the spindle is stopped. And also the measuring method of run-out, dynamic error of tool system, is studied when the spindle is rotated in 8,000 ~ 60,000 rpm. The dynamic phenomena of tool-setup is analyzed by implementing the monitoring system of rotating tool system and the noncontact measuring system of micro displacement in high speed.
디젤자동차 Brake Booster용 분리형 Vacuum Pump 개발
박경택(K. T. Park),박태조(T. J. Park),박춘욱(C. W. Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
In this paper, a separate type vacuum pump with single vane was designed and manufactured for brake booster of diesel vehicles. The CATIA software was applied in modeling of vacuum pump components and the elastohydrodynamic lubrication analysis was carried out to predict the lubrication conditions between the vane tip and inner surface of casing. The results showed that fully hydrodynamic lubrication condition can be sustained even at lower speeds, and high vacuum performance was obtained. Therefore the results obtained can be used in improvement of all types of vacuum pump.
박경택(K. T. Park),박태조(T. J. Park),강병루(B. R. Kang) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
A highly sensitive pressure regulator is required in natural gas vehicle(NGV), which are widely provided throughout the land, to maintain a constant outlet pressure regardless of inlet pressure. Successful operation and higher performances of a high pressure gas fuel management system requires complete understanding of the flow and temperature characteristics inside the regulator. In this paper, the computational fluid dynamics(CFD) code, FLUENT is adopted to investigate gas flow characteristics to design a new high performance regulator. Detailed pressure, velocity vector and temperature distributions are obtained for various inlet supply pressures and valve opening ratios. Small valve opening for high inlet pressure results in higher pressure and temperature drops under Joule-Thomson effects. Therefore the results of present study can be used in designing of a new CNG regulator.