• 한국소음진동공학회논문집
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• 제25권6호
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• pp.426-431
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• 2015

In this work, a new type of MR damper with additional flow path in piston is proposed and damping force characteristics are numerically evaluated. Flow-mode type MR damper is considered and mathematical model is established based on Bingham rheological model of MR fluid to obtain accurate prediction of damping force characteristics. Damping force of the proposed MR damper are calculated with respect to piston velocity and input current. In addition, investigation on damping force characteristics is carried out according to number of additional flow path and excellence of the proposed MR damper is demonstrated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1075-1080
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• 2008

An engine for marine propulsion and power generation consists of several cylinder liner-piston sets. And the oil groove is on the cylinder liner inside wall for the lubrication between a piston and cylinder. The machining process of oil groove has been carried by manual work so far, because of the diversity of the shape. Recently, we developed an automatic grinding robot system for oil groove machining of engine cylinder liners. It can covers various types of oil grooves and adjust its position by itself. The grinding robot system consists of a robot, a machining tool head, sensors and a control system. The robot automatically recognizes the cylinder liner's inside configuration by using a laser displacement sensor and a vision sensor after the cylinder liner is placed on a set-up equipment.

• 한국분무공학회지
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• 제9권4호
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• pp.46-52
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• 2004

An LPG engine (KL6i) for heavy duty vehicle has been developed using liquid phase LPG injection (LPLi) system, which has regarded as one of next generation LPG fuel supply systems. For the KL6i engine, lean burn technology was introduced to minimize the thermal loading and NOx emissions due to an increase of the engine power. In this work, injection timing and piston bowl shape were investigated for the stabilization of lean burn characteristics. Experimental results reveals that fuel stratification induced by these parameters is most effective strategy to extend lean combustion limit in the LPLi system.

• 대한기계학회논문집
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• 제12권5호
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• pp.1197-1205
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• 1988

본 연구에서는 피스톤운동을 톱날파로 근사하였을 때 단열된 실린더를 갖는 스터링기관에 대한 해석적인 해를 구하고자 한다. 실제기관에서 피스톤운동은 기구 학적 구동기구에 따라 상이하지만 대략적으로 정현파가 되며, 이 경우에는 해석적인 해가 존재하지 않으므로 수학적으로 구간선형적인 톱날파로 근사하였다. 비록 이러 한 근사를 도입한 단열해석이라 하더라도 해석적인 해가 존재한다면 등온해석보다는 기관성능의 예측에 더욱 적합함은 당연하다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2002년도 춘계학술대회논문집
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• pp.141-146
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• 2002

The cast iron cylinder liner of the marine engine must be scrapped after its inner surface was definitely worn out due to the friction between the surface and piston ring during the operating. In this research, the restoring method of the worn out cast iron cylinder liner are discussed based on the results of experimental work of the thermal plastic deformation technique.

• Advances in biomechanics and applications
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• 제1권2호
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• pp.127-141
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• 2014

A preliminary study of a new pulsatile pump that will work to a frequency greater than 1 Hz, is presented. The fluid-structure interaction between a Newtonian blood flow and a piston drive that moves with periodic speed is simulated. The mechanism is of double effect and has four valves, two at the input flow and two at the output flow; the valves are simulated with specified velocity of closing and reopening. The simulation is made with finite elements software named COMSOL Multiphysics 3.3 to resolve the flow in a preliminary planar configuration. The geometry is 2D to determine areas of high speeds and high shear stresses that can cause hemolysis and platelet aggregation. The opening and closing valves are modelled by solid structure interacting with flow, the rhythmic opening and closing are synchronized with the piston harmonic movement. The boundary conditions at the input and output areas are only normal traction with reference pressure. On the other hand, the fluid structure interactions are manifested due to the non-slip boundary conditions over the piston moving surfaces, moving valve contours and fix pump walls. The non-physiologic frequency pulsatile pump, from the viewpoint of fluid flow analysis, is predicted feasible and with characteristic of low hemolysis and low thrombogenesis, because the stress tension and resident time are smaller than the limit and the vortices are destroyed for the periodic flow.

• 드라이브 ㆍ 컨트롤
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• 제14권4호
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• pp.1-8
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• 2017

The Down-the-Hole hammer is one of the pneumatic drill equipment used for grinding, drilling, and mining. One the advantages of which is that a reduction work efficiency at deep site are relatively small compared to other drilling methods. Due to the large vibration in the underground area, it is difficult to measure the performance of the hammer, and hammer testing requires substantial production cost and operating expenses so research on the development of the hammer is insufficient. Therefore, this study has developed a dynamic simulation model that apprehends the operating principles of an 8-inch DTH hammer and calculates performance data such as performance impact force, piston speed, and BPM. By using the simulation model, design factors related to strike force and BPM were selected, and the influence of each design factors on performance was analyzed through ANOVA analysis. As a result, be the most important for BPM and the strike force are position of upper port that push the piston in the direction of the bit and in BPM, the size of the empty space between the bits and the piston is the second most important design factor.

• 연구논문집
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• 통권25호
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• pp.91-98
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• 1995

Recently, improving the energy efficiency of a pneumatic system and reducing the consumption of compressed air were a concern of scholars at domestic and abroad. The using fields of a pneumatic system are widely used in factory automation of manufacturing line, chemical factories with explosiveness danger and petroleum industries etc. In particular, pneumatic cylinder is applied to feeding work of workpiece. jig tools and press mechanism, reciprocation and rotary motion with rack and pinion. In this study, the experimental apparatus consisted to pneumatic cylinder, dual supply pressure regulator and solenoid valve. The dual supply pressure regulator connected to outlet port of solenoid valve. The supply pressure($4.5kg_f/cm^2$) of compressed air goes into the rodless chamber 1 to drive the piston rod forward which is named working stage. The supply pressure ($2kg_f/cm^2$) of compressed air goes into the rod chamber 2 to drive the piston rod backward which is named no-working stage. Accordingly, the research results of this study can be obtained to Energy-Saving Effects of the compressed air about 35%.

• Geosystem Engineering
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• 제21권6호
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• pp.344-351
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• 2018

It is reported that the flooding rate in low permeability sandstones is low and the oil recovery is hard to increase after water breakthrough. Understanding characteristics of waterflood is hence important for the recovery improvement. In this work, flooding tests on low permeability sandstones were conducted. The corresponding flooding characteristics were investigated by means of CT scanning and Nuclear Magnetic Resonance. Effects of irreducible water and different rates were also discussed in detail. Experimental results reveal a piston-like displacement at a low rate in low permeability samples. The saturation profile is steep and almost vertical to the forward direction. The results at a low rate confirm that once water broke through, increasing the flooding rate or flooding time can hardly reduce the remaining oil inside the sample. It is probably due to the high pore-throat ratio proven by rate-controlled mercury. Results also confirm that the presence of initial water enhanced sweep efficiency substantially. On one hand, because water had previously occupied the small pores, the subsequent oil can only invade relatively large pores and became more movable. On the other hand, stable collars can not form due to the steep front, which may suppress the snap-off.

• 한국초전도ㆍ저온공학회논문지
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• 제20권3호
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• pp.21-27
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• 2018

It is difficult to fabricate and maintain moving parts of expander at cryogenic temperature. This paper describes numerical analysis and experimental investigation on a cryogenic reciprocating expander without moving piston. An intake valve which takes high-pressure gas, and an exhaust valve which discharges low-pressure gas, are connected to a tube. The inside pressure of the tube is pulsated for work production. This geometric configuration is similar to that of pulse tube refrigerator but without regenerator. An orifice valve and a reservoir are installed to control the phase of the mass flow and the pressure. At the warm end, a heat exchanger rejects the heat which is converted from the produced work of the expanded gas. For the numerical analysis, mass conservation, energy conservation, and local mass function for valves are used as the governing equations. Before performing cryogenic experiments, we carried out the expander test at room temperature and compared the performance results with the numerical results. For cryogenic experiments, the gas is pre-cooled by liquid nitrogen, and then it enters the pulse tube expander. The experiments are controlled by the opening of the orifice valve. Numerical analysis also found the expander conditions that optimize the expander performance by changing the intake pressure and valve timing as well as the opening of the orifice valve. This paper discusses the experimental data and the numerical analysis results to understand the fundamental behavior of such a newly developed non-mechanical expander and elucidate its potential feature for cryogenic application.