• 오토저널
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• 제10권6호
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• pp.39-47
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• 1988

A disk photo sensor system was constructed and installed on engine for the crank angle measurement. Statically measured TDC crank angle data were compared with those obtained from engine motoring. Two groups of cylinder pressure data were compared each other, one measured by pressure transducer mounted flush on the combustion chamber and the other obtained with the help of spark plug type adaptor. A simple analysis on the gas flow in the spark plug type pressure transducer displayed reasonably good agreement with those from engine motoring tests. In various firing tests, the IMERs obtained from the spark plug type pressure transducer turned out to be higher than those from the flush mounted one at low engine speed while those two were nearly the same at high engine speed. As the engine load decreased the relative difference in IMEP measurement between the two types tended to be enlarged.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.742-747
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• 2004

Hard disk drives (HDD) in computer are used extensively as data storage capacity. PIV measurement system was used fur 2-dimensional visualization of the unsteady flow between co-rotating disks in air both with a shroud and both with a actual-like case. Geometric parameters are gap height (H) between disks in the case of shroud. The lobe- structured boundary between inner region and outer region was visualized, and the number of dominant vertices was determined clearly. It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as R $e_{H}$ =ΩRH/v ranging from 7.96$\times$10$^2$ to 1.43$\times$10$^4$, and decreases as the disk speed increases. In the case of a actual-like case, the boundary between inner region and outer region appears cleary when head position located at outer diameter with no damper. It is detected with a case of head position middle diameter that the tip wake is generated behind HGA using PIV measurement and calculation.n.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.65-68
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• 2006

Experiments were performed to investigate the effects of mud-flap width on the aeroacoustic noise generation inside high-speed trains. The open-circuit type wind tunnel was used. The measurement setup was custom-built to simulate intercoach spacing. From the measurements, the characteristics of the turbulent flow after the intercoach spacing and consequent generation of aeroacoustic noise inside the cabin was investigated. Especially the effects of mud flap length on the characteristics of the characteristics of the turbulent flow were identified. The mechanism of noise generation by analyzed interactions with structure vibration characteristics and generation characteristics of blocked pressure was investigated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.150-157
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• 1999

As the customer demands thickness quality stricter, new techniques of automatic thickness control(AGC), is adopted to continuous cold rolling mills. The cold rolling mills of Pohang Works have revamped the existing conventional AGC system that control the thickness at all-stands automatically by the mass flow AGC based on the measurement of strip-speed and thickness between mill stands. The No. 2 Cold Rolling Mill be has adopted the New AGC system since Oct. 1995, and The No.1 Cold Rolling Mill since June. 1999. Thanks to the New AGC system, precise control of thickness is possible not only at constant rolling speed region, but also during line speed up and down. This report describes application techniques of the New AGC system and performance of the system.

• Journal of Mechanical Science and Technology
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• 제14권12호
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• pp.1412-1420
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• 2000

The objectives of the study are to investigate the effect of swirl on the flame propagation and to propose a flame propagation model that predicts the behavior of the flame front in the presence of significant swirl flow field by analyzing flame images pictured with a high speed digital video at idle. The velocity distribution of the charge in the cylinder was measured using an LDV measurement system. From the experimental results and analyses, a new flame propagation model is proposed in which flame frontal locations can be traced by superposing the convective flow field and the uniform expansion speed of the burned gas, and the proposed model reveals that the increase of the flame propagation speed on the presence of swirl motion within 1 ms after ignition is mainly due to the flame stretch, and mainly due to increased turbulence intensity later than 1 ms after ignition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.676-681
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• 2003

In this paper, we investigated the disc warping in high-speed slim-type optical disc drive. Recently, the information storage devices are increasing track density and higher rotation speed to enhance their recording capacity and their data transfer rate. Generally, ODD used in the Lap-top Computer has small inner space. So, the flow instability of inner space is rapidly increased as its higher rotation speed. An extreme case, the flow instability causes the malfunction of readout at pick-up of drives. The experiments and numerical analysis were carried out for several cases, the result shows the influence of airflow to the disc warping.

• 정보저장시스템학회논문집
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• 제2권2호
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• pp.156-162
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• 2006

In this paper, we have investigated the disc warping in high-speed slim-type optical disc drive. The track density as well as high rotational speed of the information storage devices must be increased to enhance their recording capacity and data transfer rate. Generally, ODD used in the Lap-top computer has small inner space. So, the flow instability of the inner space is increased rapidly with its rotational speed. In extreme case, the flow instability may cause the malfunction of the read/write pick-up of drives. The experiments and numerical analysis were carried out for several cases and the result shows the influence of airflow to the disc warping.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.36-39
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• 2005

Information on temporal evolution of whole velocity fields is essential for physical understanding of a complicated turbulent flow and was obtainable using dynamic PIV because of advances of high-speed imaging technique, laser and electronics. A dynamic PIV systme consists of a high-speed CMOS camera having $1K\times1K$ pixels resolution at 1 KHz and a high-repetition Nd:Yag pulse laser. In order to validate its performance, the dynamic PIV system was applied to a turbulent jet whose Reynolds number is about 3000. The particle images of $1024\times512$ pixels were captured at a sampling rate of 4 KHz. The dynamic PIV system measured successfully the temporal evolution of instantaneous velocity fields of the turbulent jet, from which spectral analysis of turbulent structure was also feasible.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• 한국유체기계학회 논문집
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• 제14권4호
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• pp.5-11
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• 2011

This study investigated on details of flow characteristics in a vaneless diffuser of a compressor with 2-dimensional impeller at various flow rates. Experiment for a low speed compressor model in a water reservoir was performed to analyze the flow field in the vaneless diffuser and volute casing, which was done by PIV measurement. It was also focused on the periodic flow patterns occurring at low flow rate near unstable operating region of the compressor. At low flow rate condition, the flow visualization clearly shows that the flow energy from impeller is highly accumulated at the compressor exit by the blockage effect of a flow damper and consequently the reverse flow occurs in the diffuser.