• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1163-1169
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• 2023

In this study, the flow characteristics of the filter system were analyzed due to the effect of the density of the filter in the triple filter system. Flow analysis was performed as a flow passing through a porous medium. The flow characteristics of each filter system were analyzed by arranging filters with different densities in the forward flow flow and the reverse flow. The arrangement order of the triple filters was excellent in the case of forward fluid flow and in the case of higher density from the inside to the outside filter. In the reverse flow filter system, the performance of the system was the best in the case of reverse order filter arrangement. As a result of the analysis, Case II, which showed a pressure drop rate of 5.65% for forward flow, was the best in the reverse direction with a pressure drop rate of 14.25%. Considering reverse and forward flows, it was found that the optimal filter arrangement was most effective when the intermediate filter was the densest, and the inner or outer filter was less dense.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.1-12
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• 1997

In an SI engine, the characteristics of the air flow is important not only for the design of the intake system geometry but also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement using the ultrasonic flow meter and hot wire flow meter was conducted at the upstream of the intake port and the throttle. At the upstream of the intake port, the pulsating flow into the cylinder affected by the pressure wave was detected directly with the flow meters instead of pressure sensors. At the upstream of the throttle, the reverse flow phenomena were showed by comparing the flow pattern measured by the hot wire air flow meter and the ultrasonic air flow meter. The results of this study can be used for the analysis of the tuning effect in the intake manifold and estimation of the error in real time measurement for the air flow rate.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.441-447
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• 1996

Sb doped SnO2(ATO:Antinomy doped Tin Oxide) thin films were prepared by a DC magnetron spttuering method using oxide target and the deposition characteristics were investigated. The experimental conditions are as follows :Ar flow rate : 100 sccm oxygen flow rates ; 0-100 sccm deposition temperature ; 250 -40$0^{\circ}C$ DC sputter powder ; 150~550 W and sputtering pressure ; ; 2~7 mTorr. Deposition rate greatly depends not on the deposition temperature but on the reaction pressure oxygen flow rate and sputter power,. when the sputter powder is low ATO thin films with (110) preferred orientation are deposited. And when the sputter power is high (110) prefered orientation appeares with decreasing of oxygen flow rate and increasing of suputte-ring pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1085-1096
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• 2000

An experimental study was performed to examine the heat and mass transfer characteristics of $LiBr-H_2O$ solution flowing over a single horizontal tube with the water vapor absorption. Effects of the flow rate and the temperature of the solution at the top of the tube, the absorber pressure and the drainage pattern were considered. The absorption rate depends highly on the absorber pressure at the low flow rate condition while on the solution inlet temperature at the high flow rate condition. Also, when the flow rate is low, the absorption performance with the sheet flow drainage appeared to be higher than that with the dripping/jet drainage. However, at the high flow rate condition, the case became reversed. The liquid film became wavy with the higher absorption rate. The waves were more probable to form with the lower flow rate and temperature of the solution, and with the higher absorber pressure.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.411-416
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• 1999

The measurement of unsteady flow rate is of vital importance to clarify and improve the dynamic characteristics in pipeline, hydraulic components and system. There is also demand for a real time flow sensor of ability to measure unsteady flow rate with high accuracy and fast response to realize feedback control of flow rate in fluid power systems. In this paper, we propose an approach for estimating unsteady flow rate through a pipeline and components under high pressure condition. In the method, unsteady flow rate is estimated by using hydraulic pipeline dynamics and the measured pressure values at two distant points along the pipeline. The distributed parameter model of hydraulic pipeline is applied with consideration of frequency dependent viscosity friction and unsteady velocity distribution at a cross section of a pipeline. By using the self-checking functions of the method, the validity is investigated by comparison with the measured and estimated pressure waveforms at the halfway section on the pipeline. The results show good agreement between the estimated flow rate waveforms and theroetical those under unsteady laminar flow conditions. the method proposed here is useful in estimating unsteady flow rate through an arbitray cross section in hydraulic pipeline and components without installing an instantaneous flowmeter.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.146-154
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• 1997

Solenoid-folw control type ABS is used with a 'dump and reapply' pressure control arrangement instead of using 2/2 (normal open/close) solenoid valves in convensional systems(sol. -sol. control type), a flow control valve is used which replaces the (no) inlet valve. The flow control valve controls fluid flow providing a nearly constant reapply rate( .theta. ) after the dump plase of ABS operation. In this study, to investigate a characteristics of brake pressure by PWM control, test rig was consisted of ABS hydraulic modulator, digital controller, pneumatic power supply and brake master cylinder. For comparison with experi- mental results, system modelling and computer simulation were performed. As a result, experiment results showed fairly agreement with the simulation. Also, it is shown that the pressure gradient (tan .theta. ) is affected by pressure, frequency, duty ratio and expressed with an exponential funtion.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.101-108
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• 2004

Recently, a semi-active shock absorber has been taking interest because of its low cost and simple structure than the active one. CFD analysis has been conducted to investigate the continuous and variable damping characteristics of the semi-active shock absorber. Also, the flow resistance characteristics of a spool valve has been examined to identify individual parameters(namely, exponent and discharge coefficient) of pressure-flow rate relation needed for the accurate valve modeling. The flow field in the damping valve was simulated using the commercial code, CFX-5.3. The numerical results showed reasonable agreement with the experimental outputs. The pressure distribution with the variation of spool opening length and volume flow rate were discussed in detail. And the continuous and variable damping performance was found clearly. The individual parameters of spool valve were obtained as a function of orifice area. The exponent and discharge coefficient were fitted in with the first and the third polynomial respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.385-390
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• 2002

To clarify the hydraulic characteristics of ice slurry which made from 6.5% ethylene glycol-water solution flowing through circular pipes of small diameter, experimental studies were performed. The flow pattern was observed and the pressure drop was measured in acrylic pipes with inner diameter of 24 mm. The results of flow visualization revealed that ice particles flowed along the top of pipes in the ranges of small ice fraction and low flow rate, while Ice particles diffused into the whole region of pipes flowed like a homogeneous flow for high flow rate and high ice fraction. An increase in frictional pressure drop was measured as the ice fraction increased in all pipes and unstable flow was observed for up-ward vertical pipe.

• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.307-317
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• 2017

In liquid-propellant rockets, POGO instability can occur, in which a fluctuation of propellant supply to the engine, a thrust fluctuation, and a structural vibration are coupled. For the prediction of this instability, it is required to provide dynamic characteristics of the pump represented as the transfer matrix correlating the upstream and downstream pressure and flow rate fluctuations. In the present study, the flow rate fluctuation is evaluated from the fluctuation of pressure difference at the different locations assuming that the fluctuation is caused by the inertia of the flow rate fluctuation. The experiments were performed in some flow conditions, and it was shown that the tendencies of dynamic characteristics are related to excitation frequencies, cavitation numbers and flow rate coefficients.

• 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.