• 한국공작기계학회논문집
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• 제11권6호
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• pp.75-82
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• 2002

Design for a quiet operation of fluid power system requires the understanding of noise and vibration characteristics of the system. It's not easy to analyze noise problem in hydraulic cylinder used in typical actuator Because they've got complex fluid dynamics. One of the fundamental problems associated with the hydraulic system is the pulsating flow in pipe lines, which can be tackled by the analysis under simplifying assumptions. The present study focuses on theoretic analysis and experimental study on the dynamics of laminar pulsating flow in a circular pipe. We analyze the propagation characteristics of the pressure pulse within a hydraulic pipe line taking into account the pulsating flow frequency variation. We also measure instantaneous pressure pulses within pipe line to identify the transfer functions. We conduct series of experiments to investigate the propagation characteristics of pressure pulse for various pressure of pulsating flow. The working fluid of the present study is ISO VG46 and the temperature ranges from 20 to $60^{\circ}$ with normal pressure at 4000kPa. The flow rate is measured by using an ultrasonic flow meter. Pressures at fixed upstream and downstream positions are measured concurrently. The electric signals of the pressure sensor are stored and analyzed using a system analyzer(PKE 983 series). The frequency is varied in the range of 10~500Hz. The Reynolds number is kept below 2,000. In the present study, boundary condition was varied by installing a surge tank and an orifice at the end of pipe. Experimental and theoretical results were compared each other under various boundary conditions.

• 대한기계학회논문집B
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• 제26권2호
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• pp.177-183
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• 2002

The field tests on the waterhammer were carried out in the pump pipeline system with an air chamber. The effects of the input variables and the design parameters for the air chamber were investigated by both the numerical calculations and the experiments. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully studied. Among the input variables used in the waterhammer analysis, the polytropic exponent, the discharge coefficient and the wavespeed had influence on the simulated results in that order, and were calibrated in comparison with the experimental results. As the initial air volume in a vessel increased, the period of waterhammer increased and the pressure variation decreased, resulting from the reduction of the rate of pressure change in the air chamber. Using smaller orifice in the bypass pipe, the pressure rise was suppressed in some degree and the pressure surge was dissipated more rapidly as time passed. The simulations were in fairly good agreement with the measured values until 1∼2 periods of waterhammer. Not only the maximum and minimum pressures in the pipe1ine but also those occurring times were reasonably predicted. The computer program developed in this study will be useful in designing the optimum parameters of an air chamber for the real pump pipeline system.

• 동력기계공학회지
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• 제9권2호
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• pp.40-44
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• 2005

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe but residual gas, is called "Blowby gas", enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the crankcase isn't vented, this causes many bad effects such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So, most automobiles are constituted with a PCV (Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new engines, engineers are designing it depending on their experiments than theoretical knowledge. Mush efforts and times are needed for new development. This study will show quantitative results to increase the possibilities of reduction of developing time.

• 소음진동
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• 제6권2호
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• pp.163-177
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• 1996

An investigation on thermohydraulic stability of flow oscillations in the CANada Deuterium Uranium-600(CANDU-6) heat transport system has been conducted. Flow oscillations in reactor coolant loops, comprising two heat sources and two heat sinks in series, are possibly caused by the response of the pressure to extraction of fluid in two-phase region. This response consists of two contributions, one arising from mass and another from enthalpy change in the two-phase region. The system computer code used in the investigation os SOPHT, which is capable of simulating steady states as well as transients with varying boundary conditions. The model was derived by linearizing and solving one-dimensional, homogeneous single- and two-phase flow conservation equations. The mass, energy and momentum equations with boundary conditions are set up throughout the system in matrix form based on a node-link structure. Loop stability was studied under full power conditions with interconnecting the two compressible two phase regions in the figure-of-eight circuit. The dominant function of the interconnecting pipe is the transfer of mass between the two-phase regions. Parametric survey of loop stability characteristics, i. e., damping ratio and period, has been made as a function of geometrical parameters of the interconnection line such as diameter, length, height and orifice flow coefficient. The stability characteristics with interconnection line has been clarified to provide a simple criterion to be used as a guide in scaling of the pipe.

• 동력기계공학회지
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• 제9권4호
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• pp.45-50
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• 2005

Characteristics of flows at T-junction duct with and without orifices are investigated in this paper. Experiments and PIV visualization were carried out for several flow rates. Two-dimensional PIV experimental apparatus was decided by numerical analysis. PIV visualization was also coded to visualize flow fields at junctions for two-dimensional case. For the PIV visualization system, Grey-Level Cross-Correlation particle tracking algorithm was used to calculate the flow fields. Vinyl chloride polymer particles of $100{\sim}150{\mu}m$ of diameter are used in this visualization. The PIV visualization results showed relatively good agreement with Experimental data.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.19-24
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• 2004

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe but residual gas, is called 'Blow by gas', enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the crankcase isn't vented, this causes many bad effects such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So most automobiles are constituted with a PCV(Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new cases, engineers are designing it depending on their experiments than theoretical knowledges. Much efforts and times are needed for new development. This study will show quantitative results to increase the possibilities.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.66-73
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• 2005

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe. But residual gas 'Blowby gas' enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the blowby gas isn't vented, this causes many bad efffcts such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So most automobiles are constituted with a PCV(Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new cases, engineers are designing it depending on their experiments than theoretical knowledges. Much efforts and times are needed for new development. This study will show quantitative results to increase the possibilities for the optimal design.

• 수산해양기술연구
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• 제22권1호
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• pp.41-48
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• 1986

Ifis recommended that the injection rate should be accurate and reliable in the input data of the performance simulation in diesel engine. Matsuoka Sin improved W. Bosch's injection ratio measurement system. Matsuoka Sin reduced length of the test pipe and set the orifice. However, it was not measured accurately to measure the injection ratio due to reflection wave. In the present thesis, the improved measurement system with combination of the conventional W. Bosch type injection ratio measurement system and Matsuoka Sin type corrected W. Bosch type was practically made. The location of orifice and throttle valve was modified and set one more back pressure valve in order to reduce the effect of reflection wave. The results according to injection condition of multi-hole nozzle are following: 1. Measurement error of injection ratio measurement system in this thesis was $\pm$ 1 %, therefore, its reliability was good. 2. The form of injetion ratio is changed from trapezoidal shape to triangle shape with increase of revolution per minute when injection amount is constant. 3. In the case of constant rpm, the initial injection ratio is almost constant regardless of the amount, meanwhile the injection period becomes longer with increase of the amount. 4. The injection pressure of nozzle isn't largely influenced with injection ratio in the case of constant injection amount and rpm, otherwise the initial injection amount is increased by 3-4% when the injection pressure is low. 5. The injection ratio isn't nearly influenced with back pressure.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제26회 추계학술대회
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• pp.232-238
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• 1997

In this paper, a theoretical method is presented to design a hydraulic control valve system that consist of an important component in the hydraulic snubber. The hydraulic snubber is used essentially to support the piping systems at power plants. To calculate the force due to pressure drop and flow rate in the valve orifice and by-pass hole, Bernoulli equation is used. The Reynolds equation are numerically analyzed in the clearance gap between the valve cone and valve seat to estimate the friction force and leakage flow rate. Based on the detailed theoretical data, we developed successfully the hydraulic snubber for power plants.

• 상하수도학회지
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• 제33권2호
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• pp.121-129
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• 2019

If sewage flows for an extended time at low velocities, solids may be deposited in the sewer. Sufficient velocity or tractive force should be developed regularly to flush out any solids that may have been deposited during low flow periods. This study aims to evaluate the periods (T) during which sewage flow greater than the minimum tractive force maintains on a spot in sewer pipe system with lower tractive force or lower velocity than expected in the design step, when a storage tank installed in a place upsteam pours water into the sewer. The effect to T of design factors of storage tank and sewer pipes was evaluated assuming the uniform flow in sewers. When the area of orifice in the storage tank is $0.062m^2$(or 0.28 m diameter), the maximum T of 31sec was maintained using the usually used preset range of values of several design factors. As the horizontal cross section of storage tank and water depth of storage tank and roughness in sewers increase, T linearly increases. Also, T linearly decreases as the diameter of a sewer pipe increases. Although T gradually decreases as the sewer pipe slope decreases to around 0.005, T decreases sharply when the slope is less than 0.003.