• Journal of ILASS-Korea
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• v.18 no.1
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• pp.55-60
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• 2013

In this study, injection flow rates and material of the solenoid sealing of the injectors were improved for the development of a di-methyl Ether(DME) common-rail system. To deliver the same amount of energy provided by injection pressure of diesel $P_{inj}$ = 160 MPa, the DME injectors need to have larger diameter of nozzle hole and more No. of hole at low injection pressure of $P_{inj}$ = 40~50 MPa. The simplified nozzle flow model, which takes account of nozzle geometry and injection condition, was employed in order to design the concept of a injector nozzle such as No. of hole, diameter of hole and diameter of needle seat, etc. Injection amount and rate were tested by diesel and DME test stand. As a result, the diameter of nozzle hole were enlarged by 0.25 mm. The diameter of the orifice in the high pressure line was increased by 1.0 mm to maintain hydraulic force in the nozzle. The material of the solenoid sealing was changed to HNBR, which was strong against the corrosive. Experimental results showed that the injection amount of the DME injector drastically increased by 191.9% comparison to that of diesel at $P_{inj}$ = 40 MPa.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.886-892
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• 2013

Hydraulic hose assemblies are used as piping components for construction machinery, automobile, aircraft, industrial machinery, machine tools, and machinery for ships. Then the reliability of hose assemblies is important because total hydraulic system, which used to deliver the fluid power ($P^*Q$) needed to flexibility in the piping system, is not operated if the hose assembly failed in the system. The data of the accelerated life test estimated through the shape parameter(${\beta}$) resulting of the Weibull distribution analysis. This study has tried to reduce the test time resulting from varying impulse pressure range and the flexing diameter. Accelerated life test model for the test results was adopted the GLL(generalized log linear) and the accelerated indexes are identified as 6.64 for the pressure and 4.46 for flexing radius. Also, it found that shape parameter is 6.19, scale parameter(${\eta}$) is $1.035{\times}108$, which were adopted the pressure 35 MPa and the flexing diameter R100 mm in the used condition.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.319-332
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• 2002

This study is focused on the characterization of an effective hydraulic conductivity in each hydrogeologic unit assumed as an equivalent continuum medium in the granitic area. Four boreholes of 3" diameter were installed and a Multi-packer system was facilitated in the selected borehole. Various in-situ tests including the fracture logging, constant injection and fall-off tests, slug and pulse tests were carried out. A hydrogeologic unit was defined into the upper and lower zones based on the variation of fracture properties and hydraulic conductivities. The difference of the result obtained by the various hydraulic tests and the effective characterization techniques on rock mass permeability are also discussed. The effective hydraulic conductivity of the upper unit was measured by two times(5.27E-10 m/s~7.57E-10 m/s) that of the lower unit(2.45E-10 m/s~6.81E-10 m/s)through the constant injection and fall-off tests.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2402-2407
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• 2007

Heat transfer distributions and friction factors in square channels (3.5 ${\times}$ 3.5 cm) with twisted tape inserts and with twisted tape inserts plus interrupted ribs are respectively investigated. Tests are performed for Reynolds numbers ranging from 8,900 to 29,000. The rib height-to-channel hydraulic diameter, e/Dh, is kept at 0.057 and test section length-to-hydraulic diameter, L/Dh is 30. The twisted tape is 0.1 mm thick carbon steel sheet with diameter of 3.3cm, length of 90cm, and 2.5 turns. The square ribs are arranged to follow the trace of the twisted tape and along the flow direction defined as axial interrupted ribs. Each wall of the square channel is composed of isolated aluminum sections. The following conclusions from the experimental study were drawn as: 1) In the 4 heating wall channel with twisted tape inserts, Nusselt number based on bottom wall temperature is enhanced by 1.2 - 1.6 times if adding the axial interrupted ribs on the bottom wall only. 2) The twisted tape with interrupted ribs under the two-sided heating condition produces the highest heat transfer performance. 3) Friction factor data obtained for the square channel with twisted tape inserts plus axial interrupted ribs are less than those in the past publications for circular tubes with axial interrupted ribs and twisted tape inserts.

• Journal of Korea Water Resources Association
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• v.38 no.7 s.156
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• pp.527-535
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• 2005

The computation of normal depth is very important for the design of channel and the analysis of water flow. Drainage pipe generally has the shape of curvature like circular or U-type, which is different from artificial triangular or rectangular channel. In this case, the computation of normal depth or the derivation of equations is very difficult because the change of hydraulic radius and area versus depth is not simple. If the ratio of the area to the diameter, or the hydraulic radius to the diameter of pipe is expressed as the water depth to the diameter of pipe by power law, however, the process of computing normal depth becomes relatively simple, and explicit equations can be obtained. In the present study, developed are the explicit normal depth equations for circular and U-type pipes, and the normal depth equation associated with Hagen (Manning) equation and friction factor equation of smooth turbulent flow by power law is also proposed because of its wide usage in engineering design.

• Membrane Journal
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• v.26 no.4
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• pp.291-300
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• 2016

Techniques for selectively separating molecules of gas and liquid states using various separation membranes have been widely used in variety of applications such as chemical, biological, pharmaceutical, and petrochemical industries. As the nanochannel diameter, inter-channel distance and length of the nanochannel of the anodic aluminum oxide (AAO) membranes can be precisely controlled, various studies to effectively separate mixture of various molecules using AAO membrane have been widely carried out. In this study, we fabricated AAO membranes of cylindrical nanochannels of various diameter sizes and of through-hole structure, that is, nanochannels of which both ends of each nanochannel are open. Using those AAO membranes of through-hole nanochannel structure, we studied the selective permeation polymer chains dissolved in a solvent based on hydraulic volume of the polymer chains. We found a precise, quantitative relationship between the radius of gyration of polymer chains that permeated through nanochannels inside AAO membrane and the diameter of nanochannels. In addition, we demonstrate that the behavior of the polymer solution flowing through nanochannel of the AAO membrane can be successfully described with the Hagen-Poiseuille relationship. It is, therefore, possible to theoretically interpret the nanoflow of the solution flowing inside the cylindrical nanochannel.

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.137-147
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• 2008

Critical and allowable shear stress acting on the mattress revetment, is presented in this study. First of all, shear stress at each spot is computed when the hydraulic power act on the waterway. Secondly, median diameter of the filling rocks is computed using shear stress and Shields coefficient which are used to decide the critical motion of the particle. Finally, the range of critical and allowable shear stress is estimated which meet the particle stability and indicated that the mattress is a stable hydraulic structure in comparison with the riprap. Therefore the required median diameter of riprap is three times higher than that of mattress. Contrarily, this study also analyzed that resisting power of mattress to shear stress is three times higher than that of riprap on the same size.

• The KSFM Journal of Fluid Machinery
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• v.9 no.1 s.34
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• pp.25-31
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• 2006

The present study investigates the effects of bleed flow on heat/mass transfer and pressure drop in a rotating channel with transverse rib turbulators. The hydraulic diameter $(D_h)$ of the square channel is 40.0mm. The bleed holes are located between the rib turbulators on leading surface and the hole diameter (d) is 4.5 mm. The square rib turbulators are installed on both leading and trailing surfaces. The rib-to-rib pitch is 10.0 times of the rib height(e) and the rib height-to-hydraulic diameter ratio $(e/D_h)$ is 0.055. The tests were conducted at various rotation numbers (0, 0.2, 0.4), while the Reynolds number and the rate of bleed flow to main flow (BR) were fixed at 10,000 and $10\%$, respectively. The results suggest that the heat/mass transfer characteristics in the internal cooling passage are influenced by rib turbulators, bleed flow and the Coriolis force induced by rotation. For the rotating ribbed passage with bleed flow, the heat/mass transfer on the leading surface is hardly affected by bleed flow, but that on the trailing surface decreases due to the diminution of main flow. The results also show that the friction factor decreases with the bleed flow.

• Journal of the Korean Institute of Gas
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• v.20 no.2
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• pp.58-65
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• 2016

Hydraulic analysis of the natural gas transmission pipeline is to determine whether adequate flow can be sustained throughout the design life of pipeline under all expected flow conditions. Many factors have to be considered in the hydraulic design of long-distance pipelines, including the nature, volume, temperature and pressure of fluid to be transported, the length and elevation of pipeline and the environment of terrain traversed. This study reviewed the available gas operation data provided by pipeline construction project in the arctic area and discussed the gas properties such as viscosity and compressibility factor that influence gas flow through a pipeline. Pipeline inside diameter was calculated using several flow equations and pipeline wall thickness was calculated from Barlow's equation applying a safety factor and including the yield strength of the pipe material. The AGA flow equation was used to calculate the pressure drop due to friction, gas temperature and pipeline elevation along the pipeline. The hydraulic design in this study was compared with the report of Alaska Pipeline Project.

• Journal of Ocean Engineering and Technology
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• v.29 no.2
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• pp.120-127
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• 2015

When a deep-seabed lifting pump is kept this device has bending and deformation in the axis due to its long length(8m). These influences can be caused a breakdown. Therefore, a mounting must be developed to keep the lifting pump safe. This paper discusses the hydraulic cylinder design of the lifting pump and structural safety estimation of the mounting using SBD(simulation-based design). The multi-body dynamic simulation method is used, which has been used in the automotive, structural, ship building, and robotics industries. In this study, the position and diameter of the hydraulic cylinder were determined based on the results of the strokes and buckling loads for the design positions of the hydraulic cylinder. A structural dynamic model of the mounting system was constructed using the determined design values, and the structural safety was evaluated using this dynamic model. According to these results, this system has a sufficient safety factor to manufacture.