• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.671-676
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• 2014

The vortex cup is proposed as a method to transport sensitive products such as silicon wafers in manufacturing. Air through the inlet nozzle located at the top of the vortex cup flows to form a swirl in the cylinder. The flow located in the lower part of the thin gap between the vortex cup and the bottom surface escapes and generates a negative pressure that can lift objects. In this research, three-dimensional numerical simulation of the air flow field in a vortex cup is performed, and a comparison of the simulation and experimental results shows very good agreement. In addition, the vortex cup length and shape that affect the negative pressure were applied to the analysis. Through the simulation results, optimum conditions for the vortex cup shape were proposed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.937-944
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• 2013

This paper describes an improved model that can be used for configuring a non-contact pneumatic head to handle a large sheet of glass. The cylindrical head model is of a large size (70 mm). It operates on vortex flow, which can simultaneously generate suction and repulsion over the flat object's surface. The head allows for the minimal non-contact lifting of objects weighing over 3N by using reference conditions (working pressure and head dimensions). Additionally, a functional flow-guide is applied for inducing a developing tangential vortex flow to increase suction and repulsion to the reference head. The cylindrical flow-guide is associated with relatively low tangential velocity. The improved model generates greater lifting force than the reference model, as verified experimentally.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.594-600
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• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat a conductive workpiece by means of high-frequency electric current caused by electromagnetic induction. Because the induction heating is a convenient and efficient way of indirect heating, it has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers an experimental investigation on the rapid heating using the induction heating and rapid cooling using a vortex tube in order to eliminate an excessive cycle time increase. Experiments are performed in the case of a steel cup mold core with various heating and cooling conditions. Temperature is measured during heating and cooling time, from which appropriate mold heating and cooling conditions can be obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.195-201
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• 2008

In the jet engines on the aircrafts cruising at high altitude over 20 km and subsonic speed, the Reynolds number in terms of the compressor blades becomes very low. In such an operating condition with low Reynolds number, it is widely reported that total pressure loss of the air flow through the compressor cascades increases dramatically due to separation of the boundary layer and the secondary-flow. But the detail of flow mechanisms causes the total pressure loss has not been fully understood yet. In the present study, two series of numerical investigations were conducted to study the effects of Reynolds number on the aerodynamic characteristics of compressor cascades. At first, the incompressible flow fields in the two-dimensional compressor cascade composed of C4 airfoils were numerically simulated with various values of Reynolds number. Compared with the corresponding experimental data, the numerically estimated trend of total pressure loss as a function of Reynolds number showed good agreement with that of experiment. From the visualized numerical results, the thickness of boundary layer and wake were found to increase with the decrease of Reynolds number. Especially at very low Reynolds number, the separation of boundary layer and vortex shedding were observed. The other series, as the preparatory investigation, the flow fields in the transonic compressor, NASA Rotor 37, were simulated under the several conditions, which corresponded to the operation at sea level static and at 10 km of altitude with low density and temperature. It was found that, in the case of operation at high altitude, the separation region on the blade surface became lager, and that the radial and reverse flow around the trailing edge become stronger than those under sea level static condition.