• 대한기계학회논문집B
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• 제20권9호
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• pp.2909-2915
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• 1996

Precise and accurate pressure measurements are obtained using deadweight piston gauges. Pressure distribution and elastic distortion in the piston-cylinder unit are the leading factors in determination of effective area. The distortion depends upon the pressure distribution in the clearance between piston and cylinder and those are coupled each other. Considering the viscosity pressure relation of oil and governing flow equation in the clearance, a new numerical iterative algorithm is developed. The disagreement between the monotonous and sharp pressure profiles is an indication that the pressure profile will be different for each piston and cylinder unit due to material variances.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.655-663
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• 2005

Tribological characteristics in the sliding parts of oil hydraulic piston pumps are very important in increasing overall efficiency. In this study, the fluid film between the valve plate and the cylinder block was measured by using a gap sensor and the mercury-cell slip ring unit under real working conditions. To investigate the effect of the valve shape, we designed three valve plates each having a different shape. One of the valve plates was without bearing pad, another valve plate had bearing pad and the last valve plate was a spherical valve plate. It was noted that these three valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rates and the shaft torque were also investigated in order to clarify the performance difference between these three types of valve plates. From the results of this study, we found that the spherical valve plate estimated good fluid film patterns and good performance more than the other valve plates in oil hydraulic axial piston pumps.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.381-382
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• 2002

The Fluid film between the valve plate and the cylinder block was measured by use of a gap sensor and the mercury-cell slip ring unit under real working conditions. During the operating periods, experiments with discharge pressure, revolution speed, and valve geometry was carried out for the fluid film on the valve plate. To investigate the effect of the valve shape, we designed two valve plates each having a different shape; the first valve plate was a plane valve plate. while the second valve plate was a spherical valve plate. It was noted that these two valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rate and the shan torque were also investigated in order to clarify the difference between these two types of valve plates. From the results of this study. we found that the spherical valve plate estimated good fluid film patterns and performance more than the other valve plate in oil hydraulic axial piston pumps.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.697-702
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• 2004

LG Electronics developed linear compressors for a household refrigerator which can reduce energy consumption up to $24\%$ by only Drop-ln instead of a conventional reciprocating compressor. The linear compressor is composed of a linear oscillating motor, a piston directly coupled with the linear motor, a cylinder and the specific discharge system of LG. Because of this free-piston structure, the position of the piston can be changeable according to the voltage variation, load variation and so on. By this reason, LG linear compressor has been in need of an additional unit to control the position of the free-piston stably. In this paper we will introduce the innovative technology which is able to operate the linear compressor without controlling the piston position like a conventional reciprocating compressor.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.255-260
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• 2004

Recently, the technologies related to the swash plate type oil hydraulic piston pump are requiring extreme technologies to overcome the limit of high efficiency in cope with high speed and pressure, and are devoted to compact the unit, to gain low noise level, and to adopt electronic technologies, and the question regarding to maximize the mechanical efficiency, that is, to minimize the torque loss by minimizing the leakage loss in the relative sliding region but these are in trade-off relation that tribological responding is very difficult. Cylinder block-valve pate in high speed relative sliding motion has the characteristics that should be extremely controlled for the optimization of these leakage loss and mechanical efficiency, and pressure resistance designing of them is important for high pressure performance. But, studies on the stress analysis of these parts have not been performed briskly, so in this paper the stress distribution and the region where the highest displacement appears are described through the static stress analysis using CATIA V5. Through the future studies on these theme, it has the purpose of finding the suitable materials for the other parts as well as cylinder block and valve plate, in cope with high pressure operation through the stress analysis with the most similar conditions for the practical operation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1097-1102
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• 2001

Seismic safety of continuous span concrete bridge can be enhanced by distributing a large seismic lateral load to each supporting pier. A new viscoelastic device called Shock Transmission Unit(STU), which is a simple cylinder-piston assembly packed with a so-called silicone putty compound, enables the lateral seismic load to be transmitted to the pier by installation of the device to movable bearings of the bridge. The seismic safety of concrete bridges having the STU depends on not only safety of the bridges globally but also safety of anchor systems which anchors the STU to concrete pier. An experimental investigation is performed to study the behavior of cast-in-place anchor and post-installed anchor subjected to shear load statically and cyclically according to different edge distance, embedment length, and anchor spacing. Finally, the experimental results are compared with results by design methods of ACI and CCD, and results by FEM analysis.

• 한국진공학회지
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• 제16권4호
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• pp.244-249
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• 2007

분동식압력계는 정밀한 압력 측정의 기준 장비로 널리 사용되고 있다. 그것은 분동압력계가 견고하고 정확하며 이동이 간편하고 압력의 정의를 물리적으로 구현할 수 있기 때문이다. 기본적으로 분동식압력계는 분동과 피스톤/실린더 장치로 구성되며 실린더 안에 직경이 꼭 맞는 피스톤이 수직으로 삽입된 구조를 갖고 있다. 측정하려는 압력은 피스톤 아래에 작용하여 윗방향 힘을 발생시키고 피스톤 위에 얹혀 있는 분동에 의해 발생하는 아랫방향 힘과 평형을 이루게 된다. 이때 피스톤 자체의 하중은 항상 작용하므로 분동식압력계는 보통 10 kPa이상의 압력 범위에서 주로 사용된다. 기존의 방식은 피스톤 아래의 높은 압력을 기준으로 사용하지만 본 방식은 피스톤 주위의 낮은 압력을 기준압력으로 사용하여 보다 더 낮은 압력의 측정이 가능하다. 본 논문에서는 이를 효율적으로 구현한 새로운 장치를 소개하고 실제로 1.33 kPa, 13.3 kPa 두 측정범위를 갖는 정밀한 저진공 게이지(MKS, CDG)를 교정, 평가한 결과에 대해서 기술하였다.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2626-2636
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• 1996

A study of soot deposition and reentrainment was carried out both theoretically and experimentally to understand behavior of soot formed by incomplete combustion in a diesel engine. Theoretically, soot deposition on engine cylinder wall and/or piston head was studied with a stagnation point flow approximation. Soot reentrainment occurred upon exhaust gas blowdown was also studied by assuming a long-normal shear velocity distribution. Experimentally, a LPG$O_2/N_2$ flame impinging on a disk, produced by a concentric tubular burner, was chosen as deposition configuration and a shear flow unit with compressed air was installed for the study of reentrainment. For selected flame configuration, soot deposition measurements were conducted and showed that the dominant deposition mechanism was thermophoresis. Distributions of gas temperature and soot number density were estimated by combining data obtained by a B-type thermocouple with a thermophoretic transport theory. Disk temperature distributions were directly measured using a K-type thermocouple. Soot size and morphology were estimated from a TEM photograph. Ratios of soot deposit to reentrained amount were measured for a wide range of shear flow velocities, which showed that the reentrainment model was reasonable.

• 한국융합학회논문지
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• 제13권4호
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• pp.307-313
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• 2022

차량 실내소음이 엔진의 고출력화와 경량화로 인해 더욱 심각해져 엔진진동의 저감의 중요성이 높아지고 있다. 최근 엔진진동 저감의 대표적인 방법으로 밸런스샤프트 부착이 제시되고 있다. 밸런스샤프트는 피스톤과 콘로드 등의 왕복운동에서 발생하는 진동을 임의의 편심질량을 이용하여 상쇄시키는 장치이다. 따라서 밸런스샤프트는 연비향상 및 차량의 승차감을 동시에 향상시킬 수 있다. 본 논문은 엔진구조로 인해 발생하는 관성력을 유도하고 이를 상쇄하기 위한 밸런스샤프트의 불평형량과 형상을 제시한다. 제시된 두가지 형상의 밸런스샤프트를 ADAMS 다물체동역학 모델로 구현하고, 이를 동역학 시뮬레이션을 통해 실제 거동상태에서의 관성력의 저감을 확인하였다.