• 한국자동차공학회논문집
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• 제22권2호
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• pp.123-133
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• 2014

Minimizing the cylinder wear and the consumption rate of cylinder oil in a large two-stroke diesel engine is of great economic importance. A motor-driven cylinder lubricator for Sulzer RT-flex large two-stroke diesel engines developed by authors is in need of improving the lubricating system to lubricate cylinder parts optimally by an electronically controlled quill device according to changes of engine load and revolution speed. In order to apply the developed accumulating distributor to an integrated cylinder lubricator by the electronically controlled system as the third research stage, the lubricating system is improved in the electronically controlled quill device with a solenoid valve. In this study, the effects of lubricator revolution speed, driving pressure(or plunger stroke) and cylinder back pressure on oil feed rate and lubrication inequality rate are investigated by using the integrated cylinder lubricator system with an accumulated distribution by the electronic control(I.C.S.), and the oil feed rate and lubrication inequality rate of I.C.S. are compared with those of the motor-driven cylinder lubricator by the electronically controlled quill system equipped with an accumulating distributor(E.D.S.). It is found that the oil feed rate of I.C.S. is smaller than that of E.D.S. due to the reduction of delivery velocity by the higher delivery pressure, and the variances of lubrication inequality rate for I.C.S. have become smaller than those of E.D.S. as the driving pressure in all experimental conditions increases, except for the driving pressure of 26 bar(plunger stroke 2 mm) at the cylinder lubricator speed of 120 rpm.

• 한국자동차공학회논문집
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• 제8권2호
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• pp.64-71
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• 2000

In order to clarify the characteristics of soot formation and oxidation in-cylinder of a diesel engine, it is necessary to diagnose accurately for combustion of in-cylinder. The past techniques for soot measurement have limitations in providing the characteristics of soot in a diesel engine, whereas, laser-based 2D imaging diagnostics have the potential to provide better temporally and spatially resolved measurements of the soot distribution. We rebuilt an optically accessible diesel engine which is similar to the conditions of a conventional engine and tried to measure soot distribution in a cylinder of the diesel engine using laser induced scattering(LIS) and laser induced incandescence(LII). Some results were acquired in this study. LIS and LII signal that show soot distribution of a in-cylinder were taken by ICCD properly. The signal of LIS was intenser than that of LII. Although they have some differences of signal intensity in early combusion period, both of signals show that they are generally similar in late combustion period, after ATDC 50 degree.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.656-661
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• 2003

Modem reciprocating air compressors have tendency to a multi-stage W-type or V-type cylinder arrangement for the purpose of high outlet pressure, compactness and low vibration and noise. A valid counter weight calculation method using the complex expression is proposed for reducing the inertia forces of the compressor. Counter weight removes only 1st forward whirl component. Counter weight formulations are applied to the six various compressor structures which are (a) 1 cylinder single-throw crank shaft, (b) 2 cylinder single-throw crank shaft (c) 2 cylinder double-throw clank shaft, (d) 3 cylinder single-throw crank shaft, (e) 4 cylinder single-throw crank shaft and (f) 4 cylinder double-throw crank shaft. The improvement of performance is verified through available vibration test.

• 한국전산유체공학회지
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• 제9권4호
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• pp.48-54
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• 2004

Vortex-shedding flows past a circular cylinder for 200≤ Re ≤ 5000 are numerically simulated with the PowerCFD code, using a finite volume method and an unstructured grid system, developed by the author. The simulation is peformed by solving the unsteady 2-D Wavier-Stokes equations with both no model and turbulence model. The resulting Reynolds number dependence of the Strouhal number and of the drag and lift coefficients is compared with both experiments and previous numerical results. It is found that, in the range of 200≤ Re ≤ 5000 the calculation method with a turbulence model is capable of producing reasonably more accurate results than that with no model for the main practically relevant parameters such as Strouhal number, drag and lift coefficients.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.185-206
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• 2018

This paper studies the non-axisymmetric 3D problem on the dynamics of the moving load acting in the interior of the hollow cylinder surrounded with elastic medium and this study is made by utilizing the exact equations of elastodynamics. It is assumed that in the interior of the cylinder the point located with respect to the cylinder axis moving forces act and the distribution of these forces is non-axisymmetric and is located within a certain central angle. The solution to the problem is based on employing the moving coordinate method, on the Fourier transform with respect to the spatial coordinate indicated by the distance of the point on the cylinder axis from the point at which the moving load acts, and on the Fourier series presentation of the Fourier transforms of the sought values. Numerical results on the critical moving velocity and on the distribution of the interface normal and shear stresses are presented and discussed. In particular, it is established that the non-axisymmetricity of the moving load can decrease significantly the values of the critical velocity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.555-559
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• 2001

A new stereoscopic PIV is developed using two CCD cameras, stereoscopic photogrammetry, and a 3D-PTV principle. The wake of a circular cylinder is measured by the developed stereoscopic PIV technique. The B mode vortical structure of the wake over the Reynolds number 300 is clearly seen by the developed technique. The arrangement of the two cameras is based on angular position. The calibration of cameras and the pair-matching of the three-dimensional velocity vectors are based on 3D-PTV technique.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.471-474
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• 2002

A new stereoscopic PIV has been constructed using two CCD cameras, stereoscopic photogrammetry, and 3D-PTV principle. The capability of the developed stereoscopic PIV was verified through a test on the Standard Images which are provided on the website of VSJ. The arrangement of the two cameras was based on angular position For the acquisition of 3D velocity vectors, 2D velocity vectors were obtained using the gray-level cross-correlation method from the two camera images and they were matched stereoscopically. The wake of a circular cylinder was measured and turbulent properties were presented.

• 대한기관식도과학회지
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• 제16권2호
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• pp.131-137
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• 2010

Background: Montgomery T-tube is widely used to maintain airway in many cases. Market-available tubes are not always fit to the trachea of each patient and need some modification such as trimming. Complications do happen in prolonged use like tracheostomy tubes. To overcome above limitations, we designed custom-made T-tube using CT data with the aid of 3D reconstruction software. Material and Method: Boundaries were extracted from neck CT data of normal person and processed by surface rendering methods. Real laryngotracheal model and tracheal inner surface-mimicking tube model were made with plaster and rubber. The main tube was designed by accumulation of circles or simple closed curves made from boundaries. Stomal tube was made by accumulation of squares due to limitation of software. Measurement data of tracheal lumen were used to custom-made T-tubes. Tracheal lumen residing portion (vertical limb) was made like circular cylinder or simple closed curved cylinder. Stomal portion (horizontal limb) was designed like square cylinder. Results: Custom made T-tube with cylindric vertical limb and horizontal limb of square cylinder was designed. Conclusion: CT data was helpful in making custom made T-tube with 3D reconstruction technique. If suitable materials are available, commercial T-tube can be printed out from 3D printers.

• Wind and Structures
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• 제30권5호
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• pp.533-546
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• 2020

Large Eddy Simulation (LES) is used to study the effects of steady slot suction on the aerodynamic forces of and flow around a wall-mounted finite-length square cylinder. The aspect ratio H/d of the tested cylinder is 5, where H and d are the cylinder height and width, respectively. The Reynolds number based on free-stream oncoming flow velocity U_∞ and d is 2.78×10⁴. The suction slot locates near the leading edge of the free end, with a width of 0.025d and a length of 0.9d. The suction coefficient Q (= U_s/U_∞) is varied as Q = 0, 1 and 3, where U_s is the velocity at the entrance of the suction slot. It is found that the free-end steady slot suction can effectively suppress the aerodynamic forces of the model. The maximum reduction of aerodynamic forces occurs at Q = 1, with the time-mean drag, fluctuating drag, and fluctuating lift reduced by 3.75%, 19.08%, 40.91%, respectively. For Q = 3, all aerodynamic forces are still smaller than those for Q = 0 (uncontrolled case), but obviously higher than those for Q = 1. The involved control mechanism is successfully revealed, based on the comparison of the flow around cylinder free end and the near wake for the three tested Q values.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1984년도 하계학술회의논문집
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• pp.226-229
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• 1984

A novel high intensity charging device has been developed for the control of the submicron particles, such as the diesel soot particulates, which are very hard to charge highly by any means of the conventional charging device. Having new corona electrodes of a multineedle disk with the corona field-control electrodes in the outer-cylinder electrode, extremely intense and stable coronas on there sharp points expanding both radially and axially are established in the corona charging region between the multi-corona -needles and an outer-cylinder electrode. As a result, the maximum corona field intensity and current density of the charging device of the standard one on soot load in laboratory tests have been 8.5KV/cm(E=$2V_m$/D(1nD/d)) and $6.5{\mu}A/cm^2$ which enhance greatly the charging of soot particles about several 100 times higher than those obtained in conventional cylinder precipitators.