• KSTLE International Journal
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• v.1 no.2
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• pp.101-106
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• 2000

Variable displacement axial piston pumps are widely used for raising the energy level of the fluid in hydraulic systems. And the regulator is the device which regulates the discharge flow of the piston pump by controlling the swivel angle. The regulator receives the hydraulic pilot pressure and controls the pump output flow depending on the machine load and engine speed. This work deals with constant power control (horsepower control) in the design of a regulator by using a bent-axis type piston pump. In order to effectively use engine power, we must keep the horsepower from the engine to the pump constant. Therefore the regulator operates the constant power control. As a result, optimum power usage is obtained by accurately following the power hyperbola. This study focused on developing a simulation model of a regulator. First, the governing equations of the regulator are derived, and analysis is performed by computer simulation, which can identify significant parameters of regulator. As a result, the variation of the swivel angle, flow rate, hyperbolic curve, inner leakage and responsibility are simulated, and significant parameters of a regulator are identified.

• Journal of Hydrogen and New Energy
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• v.28 no.3
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• pp.308-314
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• 2017

Jet pump in automotive fuel tank module is used to deliver fuel to fuel pump so that the pump is operated without aeration in suction side. In this study, three dimensional simulation model of jet pump is developed to understand performance variation over design parameters. Performance of jet pump is also investigated experimentally in terms of operating pressures. The experimental data is used to verify the three dimensional simulation model of jet pump. Verification results show that the three dimensional simulation model of jet pump is about 1% error with experiment. The simulations are conducted in terms of throat ratio and primary flow induction angle. As the throat ratio is increased, the flux ratio is trade-off at 3 times of throat diameter. On the other hand, as primary flow induction angle is increased, vapor pressure inside the nozzle is decreased. In summary, the results show that liquid jet pump has to be optimized over design parameters. Additionally, high velocity of induced flow is able to evolve cavitation phenomena inside the jet pump.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.32-40
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• 2000

A study on the fluid flow with ultrasonic forcing was carried out to get the enhancement of turbulence by laying emphasis on the ultrasonic incidence angles and reflectors. A large water tank was made of the transparent acrylic plates and city water of $25^{\circ}C$ was used as working fluid. 7 angles ($30^{\circ},\;45^{\circ},\;60^{\circ},\;90^{\circ},\;120^{\circ},\;135^{\circ},\;150^{\circ}$) as the ultrasonic incidence angle and 4 materials (wood, acryl, glass, iron) as the reflector were selected arid experiments for the above were made. The velocity vector distribution, kinetic energy and turbulence intensity of the turbulence flow fields enhanced by ultrasonic forcing were measured, compared and discussed by using the PIV measurement which was possible to measure the velocities of simultaneous multipoints. In results, it was cleared that the incidence angle of ultrasonic and material of reflector influenced the enhancement of turbulence.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.395-402
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• 2017

The local heat transfer and total pressure drops of developed turbulent flows in the ribbed rectangular convergent/divergent channels with ${\Lambda}/V-shaped$ ribs have been investigated experimentally. The channels have the exit hydraulic diameter ($D_{ho}$) to inlet hydraulic diameter ($D_{hi}$) ratios of 0.67 for convergence and 1.49 for divergence, respectively. The ${\Lambda}/V-shaped$ ribs with three different flow attack angles of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ are manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (S) to height (e) of 10 on the walls. Thermal performances of the ribbed rectangular convergent/divergent channels are compared with the smooth straight tube under identical pumping power. The results show that the flow attack angle of $45^{\circ}$ with ${\Lambda}-shaped$ rib has the greatest thermal performance at all the Reynolds numbers studied in the convergent channel; whereas, the flow attack angle of $60^{\circ}$ with V-shaped rib has the greatest thermal performance over Reynolds number of 30,000 in the divergent channel.

• Journal of the Korean Society of Visualization
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• v.18 no.1
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• pp.67-73
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• 2020

Flexible structures have been adopted in heat transfer systems as vortex generators. The flexible vortex generators immersed in a flow show a self-sustained oscillatory motion, which enhances fluid mixing and heat transfer. In the present study, the vortex generators in a two-dimensional channel flow are numerically investigated, and they are symmetrically mounted on the upper and lower walls with an inclination angle. The momentum interaction and heat transfer between the flexible vortex generators and the surrounding fluid are considered by using an immersed boundary method. The inclination angle is one of the important factors in determining the flapping kinematics of the flexible vortex generators. The flapping amplitude increases as the inclination angle increases, thereby enhancing fluid mixing. The heat transfer is enhanced up to 80% comparing to the baseline channel flow.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.81-88
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• 2011

The triple eccentric butterfly valve has metal sheet and this study about butterfly valve ceiling is an innovative approach. But it is affected by the static pressure as well as cross-current. The damage at the valve on the pipe resulted from the reflux is due to valve leakage. This study is investigated on the triple eccentric disk and it is applied with angle and the static pressure in all cases to develop cross-current triple eccentric butterfly valves. The disc with the diameter of 300A is valve against flow velocity. The entrance pressure by flow characteristics is performed with numerical analysis. As the result, valve torque production is reduced more than the conventional triple eccentric valve and entrance pressure is decreased on the increase of valve open angle. And flow coefficient can be known to be increased.

• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.333-348
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• 2023

In this study, a 3D model of the proton exchange membrane fuel cell is established, and a new 3D baffle structure is designed, which is combined with the parallel flow field and then optimized by numerical simulation methods. The number of baffles and the cross-sectional trapezoidal base angle are taken as the main variables, and their impacts on the performance indexes of the cathode side are analyzed. The results show that the 3D baffle can facilitate the convection and diffusion mass transfer of reactants, improve the uniformity of oxygen distribution, enhance the drainage capacity, and make the cell performance superior; however, too small angle will lead to excessive local convective mass flux, resulting in the decrease of the overall uniformity of oxygen distribution and lowering the cell performance. Among them, the optimal number of baffles and angle are 9 and 58°, respectively, which improves the net output power density by 10.8% than conventional flow field.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.293-299
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• 2015

We analyzed the damage effect on Glass Fibre Reinforced Plastics(GFRP) under air flow by irradiation of continuous wave near-IR laser. Damage process and temporal temperature distribution were demonstrated and material characteristics were observed with laser intensity, surface flow speed and angle. Surface temperature on GFRP rapidly increased with laser intensity, and the damaged pattern was different with flow characteristics. In case of no flow, penetration on GFRP by burning and flame generation after laser irradiation was appeared at once. GFRP was penetrated by the heat generated from resin ignition. In case of laser irradiation under flow, a flame generated after burning extinguished at once by flow and penetration pattern on GFRP were differently shown with flow angle. From the results, we presented the damage process and its mechanism.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.137-146
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• 2002

This paper presents a quasi-3-dimensional calculation method considering secondary flows in the impellers of diagonal flow blowers. A Quantitative estimation of the secondary flow effects is made by using secondary flow theories. In order to verify the validity of the adopted models, that is, span-wise mixing model and the tip clearance model, numerical simulations are performed for two different types of impellers of diagonal flow blowers which are designed differently. Numerical experiments are conducted for each of a constant tangential velocity type impeller, and a free vortex type impeller, both at two different flow coefficients. According to the simulation results, it was found that the present model considering span-wise mixing and tip clearance effect shows better agreements with the experimental data than those without these models in terms of the flow velocity and the angle distribution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.506-517
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• 2000

One dimensional performance model has been used for the design of torque converter. The model is based on the concept of constant mean flow path and constant flow angle. These constant-assumed para meters make the design procedure to be simple. In practice, some parameters are usually replaced with geometric raw data and, the constant experiential correction factors have been used to minimize the design error. These factors have no definite physical meaning and so they cannot be applied confidently to the other design condition. In this study, the detail dynamic model of torque converter is presented to establish the theoretical background of correction factors. To verify the validity of theoretical model, steady state performance test was carried out on the several input speed. The oil temperature effect on the performance is analysed and adjusted. The constant equivalent flow angles are determined at a part of performance region by comparing the theoretical model and the test data. The sensitivity of correction factors to the input speeds are studied and the change of torus flow is presented.