• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1747-1751
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• 2008

Electrohydrodynamic jet printing (EHDP) technique is widely used for the direct writing. However, in the existing EHDP method, the printing characteristics are affected by the printing substrate used, and the line width of the printed is determined by the geometry of the nozzle. We propose an EHDP method which is capable of (1) removing the effect from the substrate, and (2) controlling the line width through the ON/OFF control of the each nozzle in the nozzle array. Printing characteristics of our EHDP system were examined and successful ON/OFF control of the nozzle array were demonstrated. By using the proposed EHDP, it is expected that stable meniscus regardless of the substrate and different line widths even using the same nozzle can be achieved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1259-1269
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• 1997

The procedure for the determination of the residual life of the pressurizer surge line nozzle in the nuclear plant is developed. The design fatigue life for the 1800 $ft^3$ pressurizer surge line nozzle in cast head design is compared with that of Westinghouse stress report, and the percentage difference between two results is less than 9%. The design fatigue life evaluation of the 1000 $ft^3$ pressurizer surge line nozzle in fabricated head design is carried out, and the consuming rate and residual life are estimated using the operating data.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.294-299
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• 2001

The old technique of sandblasting which has been used for decoration of glass surface has recently been developed into a powder blasting technique for various materials, capable of producing micro structures larger than 100 m. This paper describes the performance of powder blasting technique in micro-line grooving of glass and the effect of the number of nozzle scanning on the depth and width of line groove. Experimental results showed that increasing the no. of nozzle scanning resulted in the increase of depth and width in grooves. Increase of width which may cause several problems in the precision machining results from wear of mask film.

• Journal of Environmental Science International
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• v.32 no.8
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• pp.555-561
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• 2023

A study is to predict the effective pulsing distance following to the pulsing pressure, nozzle diameter, filtration velocity using numercial analysis techniques and use it as an efficient operation condition and economic data for on-line type pulse air jet bag filter. Filtration area 6 m² condition, calculate filter resistance coefficient for simulation through the primary experiments using coke dust. For CFD simulation, analysis pulsing characteristics about nozzle diameter, filtration velocity and pulsing pressure. The maximum pulsing length of on-line type pulse air jet bag filter, in 10mm nozzle, filtration velocity 1.5m/min and pulsing pressure 5 bar conditions, is 2,285 mm, maximum length is 76.2% of the total filter bag, which is sufficient to pulsing. In 12mm nozzle, pulsing pressure 5 bar and filtration area 1.22 m² conditions, the maximum pulsing length of on-line type pulse air jet bag filter is 1,744~2,952 mm, and the maximum length is 2,952 mm indicates pulsing air can be reached to the bottom of filter bag. When the nozzle diameter is increased 8mm to 10mm, maximum pulsing length is extended 40~47%, and increased 10mm to 12 mm, maximum pulsing length is extended 10~17%. For effective pulsing, over the 5bar of pulsing pressure and larger than 10 mm of nozzle diameter are required.

• Journal of Mechanical Science and Technology
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• v.17 no.4
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• pp.617-625
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• 2003

Effects of Injector nozzle geometry and operating pressure conditions such as opening pressure, ambient pressure. and injection pressure on the transient fuel spray behavior have been examined by experiments. In order to clarify the effect of internal flow inside nozzle on the external spray, flow details Inside model nozzle and real nozzle were alto investigated both experimentally and numerically. for the effect of injection pressures, droplet sizes and velocities were obtained at maximum line pressure of 21 MPa and 105 MPa. Droplet sizes produced from the round inlet nozzle were larger than those from the sharp inlet nozzle and the spray angle of the round inlet nozzle was narrower than that from the sharp inlet nozzle. With the increase of opening pressure, spray tip penetration and spray angle were increased at both lower ambient pressure and higher ambient pressure. The velocity and size profiles maintained similarity despite of the substantial change in injection pressure, however, the increased injection pressure produced a higher percentage of droplet that are likely to breakup.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1280-1287
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• 2002

The old technique of sandblasting which has been used for decoration of glass surface has recently been developed into a powder blasting technique for brittle materials such as glass, silicon and ceramics, capable of producing micro structures larger than $100{\mu}$ m. This paper describes the performance of powder blasting technique in micro-line grooving of glass and the effect of the number of nozzle scanning on the depth and width of line groove. Experimental results showed that increasing the no. of nozzle scanning resulted in the increase of depth and width in grooves. Increase of width which may cause several problems in the precision machining results from wear of mask film. Therefore, well-controlled masking process is the most important factor for micro machining of glass with accuracy.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.211-219
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• 2016

To develop an ash separator for the solid fuel chemical looping combustion system, effects of operating variables such as solid injection nozzle velocity, diameter of solid injection nozzle, gap between solid injection line and vent line, vent line inside diameter, and solid intake height on solid separation rate and solid separation efficiency were measured and discussed using heavy and coarse particle and light and fine particles mixture as bed material in an acrylic fluidized bed apparatus. The solid separation rate increased as the solid injection nozzle velocity and the diameter of solid injection nozzle increased. However, the solid separation rate decreased as the gap between solid injection line and vent line, the vent line inside diameter, and the solid intake height increased. The solid separation efficiency was in inverse proportion to the solid separation rate. In this study, we could get high solid separation rate up to 2.39 kg/hr with 91.6% of solid separation efficiency.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.337-345
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• 2002

The present study addresses a computational result of unsteady gas flow through a critical nozzle. The axisymmetric, unsteady, compressible, Wavier-Stokes equations are solved using a finite volume method that makes use of the second order upwind scheme for spatial derivatives and the multi-stage Runge-Kutta integral scheme for time derivatives. The steady solutions of the governing equation system are validated with the previous experimental data to ensure that the present computational method is valid to predict the critical nozzle flows. In order to simulate the effects of back pressure fluctuations on the critical nozzle flows, an excited pressure oscillation with an amplitude and frequency is assumed downstream of the exit of the critical nozzle. The results obtained show that for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of critical nozzle, and thus giving rise to the applicable fluctuations in mass flow rate through the critical nozzle, while for high Reynolds numbers, the pressure signals occurring at the exit of the critical nozzle do not propagate upstream beyond the nozzle throat. For very low Reynolds number, it is found that the sonic line near the throat of the critical nozzle remarkably fluctuateswith time, providing an important mechanism for pressure signals to propagate upstream of the nozzle throat, even in choked flow conditions. The present study is the first investigation to clarify the unsteady effects on the critical nozzle flows.

• Journal of the Korean Society of Visualization
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• v.9 no.2
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• pp.48-53
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• 2011

The shape of nozzle cross-section plays an important role in stabilizing electrospray jet. The angle of contact line is governed based on the famous Young-Laplace equation. Compared to a round nozzle that has a constant curvature along the orifice, the square nozzle has four square corner edges and four straight edges that hold the meniscus in a different manner and is of interest in this study. By utilizing both square and round capillary nozzle, we examine the effect of nozzle shape in electrohydrodynamic jetting. The ejections were recorded with a high speed camera and analyzed to examine the jetting repeatability based on dynamic movement of meniscus. The result suggests that if the corner edges are not sharp, then its effect on repeatability is also limited.

• Advances in aircraft and spacecraft science
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• v.1 no.4
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• pp.399-408
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• 2014

The flowfields inside a contour and a conical nozzle exhausting into a straight cylindrical supersonic diffuser are computed by solving numerically axisymmetric turbulent compressible Navier-Stokes equations for stagnation to ambient pressure ratios in the range 20 to 34. The diffuser inlet-to-nozzle throat area ratio and exit-to-throat area ratio are 21.77, and length-to-diameter ratio of the diffuser is 5. The flow characteristics of the conical and contour nozzle are compared with the help of velocity vector and Mach contour plots. The variations of Mach number along the centre line and wall of the conical nozzle, contour nozzle and the straight supersonic diffuser indicate the location of the shock and flow characteristics. The main aim of the present analysis is to delineate the flowfields of conical and contour nozzles operating under identical conditions and exhausting into a straight cylindrical supersonic diffuser.