• Tunnel and Underground Space
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• v.21 no.3
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• pp.164-173
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• 2011

In the present study, the stability of a compressed air energy storage cavern was numerically assessed by concrete plug shapes in order to investigate the optimal shape of concrete plug. The concrete plugs were cylindrical, embedded cylindrical, tapered, and wedged in shape. The stability assessment was carried out based on factor of safety through a strength reduction method and a volume ratio which refers to the ratio of the volume of yield regions in concrete induced by internal pressure to all concrete volume. The results from the present study indicated that the embedded cylindrical and taper shaped plugs were mechanically more stable than the cylindrical and wedge shaped plugs. However, from a comparison of stress distributions in rock mass between the embedded cylindrical and taper shaped plugs, the taper shaped plug was found to be more optimal than the embedded cylindrical plug, since the embedded cylindrical plug caused more stress concentration in the interface between the plug and rock mass than the taper shaped plug.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.259-264
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• 2000

The functions of the plug valve are the control of flow rate as well closing and opening pipe lines. Analyses on the flow characteristics in plug valve port are required to improve the performance and safety at severe operating conditions such as high-pressure and high-temperature. In this study, numerical analyses are carried out with varying the opening rate (fraction of the full open to close) of the valve and the shapes of valve Uk: straight, convex, concave and mixed shapes. The parameters influencing the flow characteristics in the valve are the discharge coefficient( $C_v$) and the resistance coefficient( K). Therefore, the distributions of static pressure, velocity vector and stream lines are investigated, and $C_v$ and K are calculated in each opening rate and shape. In case of full open, the static pressure passed through the valve port has almost been recovered. However, in case of other opening rates, the pressure does not permanently regained due to pressure drop leading to loss. This phenomenon in each shape of the valve shows the different behaviors. Calculation results show that the mixed shape has the best flow attribute.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2423-2430
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• 1994

Several factors of the efficient combustion process are shape of combustion chamber, position of spark plug, turbulence flow and so on. the shape of combustion chamber and position of spark plug are constrained to geometrically, and then it could not make a change the shape easily. But the turlence flow in combustion chamber have a great influence on combustion phenomena, and which is much easier to control relatively. And since characteristics of turbulence flow would be very important to the stability of combustion and performances, This study is also essential to future engine-low emission and lean burn engine. This paper shows that the visualization of the turbulence flow of single cylinder engine by using 2way, $45^{\circ}$ inclined and 2 channel hot wire probe through the park plug hole. We also study the characteristics of turbulence flow by means of ensemble averaged mean velocity, turvulence intensity and integral length scale.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.5
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• pp.207-214
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• 2017

In this study, failure behavior of piercing plug for seamless tube manufacturing process was studied. Three different kinds of passed piercing plugs (10, 90, 215 times) were prepared. The shape deformation of the passed piercing plugs was observed by 3D coordinate measuring machine, and the oxidized layer on the surface of piercing plug was observed by optical microscopy. The length reduction of piercing plug presented at 215 times passed plug. It was found that the oxidized layer consisted of outer scale, inner scale and internal oxidation layers, and the inner scale layer had vertical cracks, and interfaces had horizontal cracks. We proposed the failure mechanism of piercing plug during seamless tube manufacturing process based on the formation of vertical and horizontal crack.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.93-103
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• 2000

The concrete plug in an underground cavern prevents the stored product (oil, gas, etc) from leaking and the excessive show of underground water, so it plays an important role in construction and operation of the storage cavern. Additionally, it should maintain its stability under every possible loading condition. Once the plug is constructed, the cavern is isolated from the external access. Therefore, mechanical and hydraulic consideration should be made in construction to fulfill its function. Therefore, in this study, numerical analyses were conducted to study the optimal shape and thickness of the plug with respect to the various conditions of installation depth, the shape of the plug, in-situ stress ratio (K), the condition of rock-plug interface, and the effect of Excavation Damaged Zone (EDZ). This paper also presents the effect of slot depth on the hydraulic behavior of the plug. These analyses were carried out by using the 2-dimensional finite difference code, rm FLAC, and the 3D code, m FLA $C^{3D}$./.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.344-354
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• 2000

The concrete plug in an underground cavern prevents the stored product (oil, gas, etc) from leaking and the excessive inflow of underground water, so it plays an important role in construction and operation of the storage cavern. Additionally, it should maintain its stability under every possible loading condition. Once the plug is constructed, the cavern is isolated from the external access. Therefore, mechanical and hydraulic consideration should be made in construction to fulfill its function. Therefore, in this study, numerical analyses were conducted to study the optimal shape and thickness of the plug with respect to the various conditions of installation depth, the shape of the plug, in-situ stress ratio (K), the condition of rock-plug interface, and the effect of Excavation Damaged Zone (EDZ). This paper also presents the effect of slot depth on the hydraulic behavior of the plug. These analyses were carried out by using the 2-dimensional finite difference code, rm FLAC, and the 3D code, rm FLAC$\^$3D/.

• Geomechanics and Engineering
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• v.12 no.1
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• pp.139-160
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• 2017

The bearing mechanism of tunnel-type anchorage (TTA) for suspension bridges is studied. Model tests are conducted using different shapes of plug bodies, which are circular column shape and circular truncated cone shape. The results show that the plug body of the latter shape possesses much larger bearing capacity, namely 4.48 times at elastic deformation stage and 4.54 times at failure stage compared to the former shape. Numerical simulation is then conducted to understand the mechanical and structural responses of plug body and surrounding rock mass. The mechanical parameters of the surrounding rock mass are firstly back-analyzed based on the monitoring data. The calculation laws of deformation and equivalent plastic strain show that the numerical simulation results are rational and provide subsequent mechanism analysis with an established basis. Afterwards, the bearing mechanism of TTA is studied. It is concluded that the plug body of circular truncated cone shape is able to take advantage of the material strength of the surrounding rock mass, which greatly enhances its bearing capacity. The ultimate bearing capacity of TTA, therefore, is concluded to be determined by the material strength of surrounding rock mass. Finally, recommendations for TTA design are proposed and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.913-918
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• 2016

A three-way reversing valve, which provides rapid and accurate changes in the water flow direction without requiring any precise control device, is used in automotive washing machines to remove oil and dirt that remain on the machined engine and transmission blocks. Because of the complicated shape of the bottom-plug, however, cavitation occurs in the plug. In this study, the cavitation index and POC (percent of cavitation) were used to quantitatively evaluate the cavitation effect occurring in the bottom-plug on the downstream side. An optimal shape design was conducted via parametric study with a simple CAE model to avoid time-consuming CFD analysis and hard-to-achieve convergence. To verify the results of the numerical analysis, a flow visualization test was conducted using a specimen prepared according to ISA-RP75.23. In this test, the flow characteristics, such as cavitation occurring on the downstream side, were investigated using flow test equipment that included a valve, pump, flow control system, and high-speed camera.

• Journal of Drive and Control
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• v.16 no.4
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• pp.32-37
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• 2019

Glove valves are used for various purposes in the process control field because such valves enable easy control of temperature and pressure. However, such valves are associated with significant loss of pressure and also have the disadvantage of complicating the shape of the cage or plug to facilitate linear flow rate change. In this paper, the shape of the plug, one of the valve flow control elements, was designed to improve the flow characteristics of the glove valve, and then CFD analysis was performed using compressible fluid. The numerical analysis results of the glove valve were analyzed according to the opening ratio and the pressure ratio of the valve. From these results, it was found that the proper notch on the side of the plug contributed to reducing the energy loss of the fluid through the valve and improving the linearity of the valve.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1163-1171
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• 2004

The variation of spark plug location have one of the effects on combustion characteristics. Several parameters of the effect on combustion characteristics are shape of combustion chamber, the spark plug position, turbulence flow and so on. This paper presents an experimental study according to variation of spark plug protrusion and PDA valve which have effects on characteristics of combustion and emission in single cylinder gasoline engine. Also, this paper emphasized that combustion stabilization was making by way of the reinforcement of the turbulent flow with the PDA valve. A feasibility and necessity of combustion pressure based cylinder spark timing control according to spark plug protrusion has been examined. So, this was obtained COV$\_$imep/ and the mass fraction burned(MFB) and the specific fuel consumption(sfc). Using the results of the test, the effects of the variable spark plug location and PDA valve can be improved fuel consumption and be available for the combustion stability.