• Korean Journal of Agricultural Science
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• v.11 no.2
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• pp.284-294
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• 1984

Effects of orifice diameter, operating angle and swirl chamber distance were examined to study a reasonable distribution pattern on the maximum available travel distance in the triple nozzle system. The results of the study were as follows; 1. Discharge rate was increased with increase of orifice diameter, and a quadratic line for the 1st nozzle and linear lines for the 2nd or the 3rd nozzle. 2. The operating angle of $15^{\circ}$ had showed the maximum available travel distance, and 17m in orifice diameter of 3.0mm and operating pressure of $24.5{\times}10^5pa$ ($25Kg/cm^2$). 3. Nozzle setting methods (reference Table 6.) for improvement of uniformity of deposit distribution were varied depending on the size of orifice diameter of the 1st nozzle, nevertheless coefficients of uniformity were improved about 6 percents. 4. Adjustment of the swirl chamber distance of the 2nd nozzle could improve the minimum area of about 6m from the triple nozzle.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.44-53
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• 2006

In this study, the non-destructive computed tomography was adopted to observe the density profile of the needle-punched Carbon/Carbon(C/C) composites nozzle throat. The density profile of C/C was evaluated within ${\pm}0.01g/cm^3$ with 98.74% confidence when the correction of the image and high signal-to-noise ratio were achieved by the optimization of the beam hardening, the electrical noise and the scattered X-ray. The density variation of C/C with the computed tomography was in good agreement with the results obtained by the water immersion method and the observation with scanning electron microscope.

• Transactions of Materials Processing
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• v.27 no.1
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• pp.18-27
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• 2018

As one of the functional metal parts in steam turbine diaphragm assembly, the hollow-partitioned turbine nozzle (stator) has large and thick geometries, as well as an asymmetric configuration. Therefore it is hard to support a metal blank in the die cavity. To ease this situation and control posture and position of metal blank (workpiece), a blank support structure is newly introduced. The blank support structure is basically composed of enlarged arms from the blank, guide pins and linear bearings. It can help to control the intermediate blank without a critical sliding phenomenon. The operation mechanism of this blank support structure, during thick plate forming for the hollow-partitioned turbine nozzle stator, is first evaluated. A series of FEM-based numerical simulations, with respect to the width of the guide arm as geometric design parameters, are carried out to investigate its applicable range. As the results, it is observed the blank support structure for this thick plate forming can guide the workpiece to have stable posture during the plate forming process.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1975-1980
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• 2004

The three-dimensional flow in a turbine nozzle guide vane passage causes large secondary loss through the passage and increased heat transfer on the blade surface. In order to reduce or control these secondary flows, a linear cascade with a contoured endwall configuration was used and changes in the three-dimensional flow field were analyzed and discussed. Measurements of secondary flow velocity and total pressure loss within the passage have been performed by means of five-hole probes. The investigation was carried out at fixed exit Reynolds number of $4.0{\times}10^5$. The objective of this study is to document the development of the three-dimensional flow in a turbine nozzle guide vane cascade with modified endwall. The results show that the development of passage vortex and cross flow in the cascade composed of one flat and one contoured endwalls are affected by the flow acceleration which occurs in contoured endwall side. The overall loss is reduced near the flat endwall rather than contoured endwall.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.576-581
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• 2001

When a liquid is supplied through a nozzle onto a relatively nonwetting inclined solid surface, a narrow rivulet forms. This work provides novel physical insights into the following phenomena in the rivulet flow that have not been well understood to date. Firstly, the fundamental mechanism behind the transition of a linear rivulet to a droplet flow is investigated. The experiments show that the droplet flow emerges due to the necking of a liquid thread near the nozzle. Based on the observation, it is argued that when the retraction velocity of a liquid thread exceeds its axial velocity, the bifurcation of the liquid thread occurs, and this argument is experimentally verified. Secondly, a discussion on the curved motion of a meandering rivulet is given. This study proposes the contact angle hysteresis as a primary origin of the centripetal force that enables the rivulet's curved motion A simple scaling analysis based on this assumption predicts a radius of curvature which agrees with the experimental observation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3148-3165
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• 1993

A cascade wind tunnel test for a turbine nozzle, which was designed for a small turbo jet engine in a previous study, has been conducted to evaluate its aerodynamic performance and losses. The large-scale blades were based on the mid-span profile of the nozzle. Oil film flow structure, and then 3-dimensional velocity components were measured in the flow passage with a 5-hold pressure probe, in addition to turbulent intensities at mid-span of cascade exit using a hot-wire anemometer. From this study, 3-dimensional growth of horseshoe and passage vortices in the downstream direction was clearly understood with near-wall flow phenomena. In addition, secondary flow and losses associated with the blade configuration were obtained in detail.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.5
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• pp.41-53
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• 1992

The main purpose of this study is to investigate the atomizing characteristics of a two phase spray by using a liquid column type coaxial nozzle. The experiments have been carried out to analyze the atomization behavior, the droplet size distributions, and the statistical properties of droplet size distributions. Immersion sampling method and the image processing technique were adapted for the measurements of particles, and the distributions of the droplet sizes were statistically analyzed. In the experiments, the mass ratio defined as Mr= $M_{\sigma}$/ $M_{1}$ has been changed from 1.0 to 3.4 and the measurements have been performed along the axis of the spray. As a result of this experimental study, the distributions of droplet size were satisfied with the Log-Normal distributions and arithmetic mean diameter and deviation of mass ratio. Droplet volume-surface mean diameter was denoted by a exponential function of mass-ratio and the exponent was denoted by linear relation according to the central axis from the nozzle. Dispersions, skewness factors and flatness factors had comparatively constant values regardless of mass ratio and location.

• Tribology and Lubricants
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• v.22 no.1
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• pp.20-25
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• 2006

The stress behavior analysis of a-rings and packing for a LPG filling unit has been presented using a finite element analysis technique by non-linear MSC/MARC program. The sealing performance and endurance of a-rings and packing are affected by working conditions such as filling pressure, friction coefficient, compression ratio, and material properties. The elastomeric polymers of O-rings and packing are nitrile butadiene rubber (NBR) and polytetrafluoroethylene (PTFE), which are selected as proper materials of a-rings and packing based on the stress analysis results. The calculated FEM results showed that the proper material of O-ring is NBR as a secondary sealing component and the recommended material of packing is PTFE as a primary sealing unit during a LPG filling process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.10
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• pp.1042-1048
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• 2001

When a liquid is supplied through a nozzle onto a relatively non-wetting inclined solid surface, a narrow rivulet forms. This work provides novel physical insights into the following phenomena in the rivulet flow that have not been well understood to date. Firstly, the fundamental mechanism behind the transition of a linear rivulet to a droplet flow is investigated. The experiments show that the droplet flow emerges due to the necking of a liquid thread near the nozzle. Based on the observation, it is argued that when the axial velocity of a liquid is slower than the retraction velocity of its thread, the bifurcation of the liquid thread occurs, and this argument is experimentally verified. Secondly, a discussion on the curled motion of a meandering rivulet is given. This study proposes the contact angle hysteresis as a primary origin of the centripetal force that enables the rivulet\`s curved motion. A simple scaling analysis based on this assumption predicts a radius of curvature which agrees with the experimental observation.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.514-519
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• 2003

The objective of this study is to document the secondary flow and the total pressure loss distribution in the contoured endwall installed linear turbine nozzle guide vane cascade passage and to propose an appropriate contraction ratio of the contoured endwall which shows the best loss reduction among the simulated cases. In this study, three different contraction ratio of contoured endwalls have been tested. This study was performed by experimental method and when the contoured endwall has the contraction ratio of 0.17 on exit height the results showed the best loss reduction.