• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.1020-1026
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• 2012

This paper proposes a new type of high-frequency directional valve controlled by the piezostack actuator associated with displacement amplifier. As a first step, a dynamic model of directional valve which can operate at 200 Hz with a flow rate of 12 litter/min is derived by considering pressure drop and flow force. As a second step, an appropriate piezostack is selected by considering actuation force as well as field-dependent displacement. Subsequently, in order to control spool displacement and flow rate a proportional-derivative(PD) controller is designed based on the 3rd-order valve system. Control performances such as sinusoidal trajectory tracking of the spool displacement in time domain are evaluated. In addition, the field-dependent flow rate is also presented to verify the required performance of the valve system.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.19-25
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• 2007

A LNG safety valve functions to control a constant pressure inside the LNG line of transportation, and the flow through it accompanies with noise and vibration which affect adversely on the system. The present study aims at understanding the flow physics of LNG safety valve for a practical design of LNG safety valve. A computational work using the two-dimensional, axisymmetric, compressible, Navier-Stokes equations is carried out to simulate the gas flow through the LNG safety valve, and compared with the theoretical results. It is found that the shape of valve sheet and the gap size are the key parameters in determining the gas dynamic forces on the valve sheet, and there exists a distance between nozzle exit and valve sheet in which the thrust coefficient at the valve sheet increases abruptly.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1237-1243
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• 2009

A computational procedure to estimate the noise radiated from a discharge valve system in a linear compressor was discussed and established. This procedure was composed of three steps. As the first step, the dynamic behavior of the valve system was estimated taking into consideration of fluid-valve-piston interactions. As the second step, the flow characteristics of refrigerant in the discharge valve system were estimated through computational fluid dynamics applying the behaviors of the valves as moving boundary conditions. The variations of pressures and velocities of fluid were converted to quadrupole noise sources. As the final step, the boundary element method based on Helmholtz equation was applied to predict the radiated acoustic pressure. The computational results by the presented procedure were experimentally validated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.7
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• pp.460-467
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• 2010

In housing units constructed recently in Korea, the length of ondol coil is different in each room, so the flow rate of hot water is adjusted by setting valve opening. If the flow rate is not appropriate for heating load, the room temperature seriously deviates from the set temperature range for comfort. In particular, too small valve opening can induce a noise by cavitation. In order to adjust the valve opening, two methods by zone area and a new method by return temperature rise were modelled and simulated using TRNSYS and EES. As a result, heating energy consumption during one week was the same on three methods, but the room temperature of the new method minimally deviated from the range of set temperature with a low possibility of noise.

• Journal of KSNVE
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• v.3 no.2
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• pp.163-167
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• 1993

Suction and discharge valves of special type refrigerant compressor are designed by finite element method for effective valve design development procedure. It is well known that valve dynamic characteristics, for example, the natural frequencies and vibration modes, are necessary for the computer simulation of compressor valve dynamics, the analysis of flow patterns, noise, impact stresses and their propagation phenomena. This paper has analysed the natural frequencies and vibration modes for the first three orders under the given special boundary conditions and the experiments are conducted by laser holography. And also stress distribution is analysed and experiment by strain gage is followed.

• International Journal of Safety
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• v.3 no.1
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• pp.6-9
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• 2004

This paper deals with the noise evaluation technique of a reciprocating air-compressor and its noise reduction. The reciprocating air-compressors are widely used in the small, medium sized industrial firms, and lots of their employees are affected and irritated by their noise in the workplace. Thus, noise control actions should be taken appropriately by considering the hearing loss due to the occupational noise exposure. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known as motor, belts, suction/discharge valves, moving pistons, and flow-induced noise caused by edges or discontinuities along the flow path e.g. expansions, contractions, junctions and bends etc .. As a result, main noise sources of the air-compressor can be categorized by the suction/discharge noise, valve noise, and compressed-air tank noise. Based on the investigations, mufflers are designed to reduce both the suction/discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, polyethylene resin is used as a new one for the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings. As a result of the countermeasure plans, it can be achieved that the noise reduction of the air-compress is up to 10dB.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.22-27
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• 2010

Flow Coefficients of intake port in an engine cylinder head were measured by a newly designed flow rig. In measuring the flow coefficient with traditional method, the valve lift was manually varied by technician with adjusting a micrometer which is directly connected to the intake valve of the cylinder head. The cam shaft of the cylinder head is directly rotated by a step motor and the valve lift was automatically varied with cam shaft profile in the newly designed flow rig. The measurement of the flow coefficient was automated by rotating the cam shaft with the step motor. Automatic measurement of the flow coefficient could be safely measured by separating a technician from the noise and vibration of the traditional flow rig. Also, the automatic measurement of the flow coefficient reduce the measurement time and provide meaningful statistical data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.35-43
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• 1999

The paper describes an approach for measuring delivery flow ripple generated by oil hydraulic axial piston pumps. In order to reduce pressure ripple which cause to undesirable noise. vibration and fatigue in hydraulic systems it is indispensible measure a delivery flow ripple from pumps. Since the flow ripple measurement of flow pumps is independent of the dynamic characteristics of the connected hydraulic circuit the measurement of flow ripple is most suitable for pump fluid-borne noise rating. The measurement of flow ripple with high frequencies from axial piston pumps is made by applying the remote instantaneous flow rate measurement method which is based on the dynamic characteristics between pressure and flow rate in hydraulic pipeline. The measured flow ripple waveforms are influenced by the configuration of V-shaped triangular relief groove in the valve plate. It can be seen that the appropriate relief groove in valve plate reduces the pressure and flow ripple amplitude and frequency spectrum for high harmonics.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.469-474
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• 2002

In recent years, modularization of engine parts has increased the application of plastic products in air intake systems. Plastic intake manifolds provide many advantages including reduced weight, contracted cost, and lower intake air temperatures. These manifolds, however, have some weakness when compared with customary aluminium intake manifolds, in that they have low sound transmission loss because of their lower material density. This low transmission loss of plastic intake manifolds causes several problems related to flow noise, especially when the throttle is opened quickly. The physical processes, responsible for this flow noise, include turbulent fluid motion and relative motion of the throttle to the airflow. The former is generated by high-speed airflow in the splits between the throttle valve and the inner-surface of the throttle body and surge-tank, which can be categorized into the quadrupole source. The latter induces the unsteady force on the flow, which can be classified into the dipole source. In this paper, the mechanism of noise generation from the turbulence is only investigated as a preliminary study. Stochastic noise source synthesis method is adopted for the analysis of turbulence-induced, i.e. quadrupole noise by throttle at quick opening state. The method consists of three procedures. The first step corresponds to the preliminary time-averaged Navier-Stokes computation with a $k-\varepsilon$ turbulence model providing mean flow field characteristics. The second step is the synthesis of time-dependent turbulent velocity field associated with quadrupole noise sources. The final step is devoted to the determination of acoustic source terms associated with turbulent velocity. For the first step, we used market available analysis tools such as STAR-CD, the trade names of fluid analysis tools available on the market. The steady state flows at three open angle of throttle valve, i.e. 20, 35 and 60 degree, are numerically analyzed. Then, time-dependent turbulent velocity fields are produced by using the stochastic model and the flow analysis results. Using this turbulent velocity field, the turbulence-originated noise sources, i.e. the self-noise and shear-noise sources are synthesized. Based on these numerical results, it is found that the origin of the turbulent flow and noise might be attributed to the process of formulation and the interaction of two vortex lines formed in the downstream of the throttle valve. These vortex lines are produced by the non-uniform splits between the throttle valve and inner cylinder surface. Based on the analysis, we present the low-noise design of the inner geometry of throttle body.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.916-923
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• 2011

The refrigerant after the expansion valve interchanges the heat at the evaporator. At this moment, the state of gas and liquid becomes two-phase flow and causes irregular noise. In order to avoid the noise, the two-phase flow pattern should be predicted. In this paper, the procedure to predict the two-phase flow patterns such as churn flow and annular flow was suggested using the CFD software. The experiments using refrigerant-supplying equipment was carried out and the noise levels according to the flow pattern were measured. The flow patterns predicted by this procedure showed good agreement with those by experiments. The churn flow is noisier than annular flow pattern.