• KSTLE International Journal
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• v.3 no.2
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• pp.79-83
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• 2002

Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindle. High speed spindle requires non-contact type of sealing mechanism. Current work emphases on the investigation of the air jet effect on the protective collar type labyrinth seal. To improve the sealing capability of conventional labyrinth seal, air jet was injected against through the leakage flow, It has a combined geometry of a protective collar type and an air jet type. Both of a numerical analysis by CFD (Computational Fluid Dynamics) and experimental measurements are carried out to verify sealing improvement The sealing effects of the leakage clearance and the air jet magnitude are studied in various parameters. The results of pressure drop in the experiment match reasonably to those of the simulation by introducing a flow coefficient Effect of sealing improvement is explained as decreasing of leakage clearance by air jetting. Thus, sealing effect is improved by amount of air jetting even though clearance becomes larger.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.594-599
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• 2008

This paper presents a micro air pump based on the synthetic jet to supply reactant at the cathode side for micro fuel cells. The synthetic jet is a zero mass flux device that converts electrical energy into the momentum. The synthetic jet actuation is usually generated by a traditional PZT-driven actuator, which consists of a small cylindrical cavity, orifices and PZT diaphragms. Therefore, it is very important that the design parameters are optimized because of the simple configuration. To design the synthetic jet micro air pump, a numerical analysis has been conducted for flow characteristics with respect to various geometries. From results of numerical analysis, the micro air pump has been fabricated by the PDMS replication process. The most important design factors of the micro air pump in micro fuel cells are the small size and low power consumption. To satisfy the design targets, we used SP4423 micro chip that is high voltage output DC-AC converter to control the PZT. The SP4423 micro chips can operate from $2.2{\sim}6V$ power supply(or battery) and is capable of supplying up to 200V signals. So it is possible to make small size controller and low power consumption under 0.1W. The size of micro air pump was $16{\times}13{\times}3mm^3$ and the performance test was conducted. With a voltage of 3V at 800Hz, the air pump's flow rate was 2.4cc/min and its power consumption was only 0.15W.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.4944-4949
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• 2012

The purpose of this paper is concerned with a development of air gun for use at work. A air gun is the tool to remove of cutting fluid and workpiece chip in industrial field used machine tool. And it generally is used to shoot a jet of compressed air. Worker must prepare respectively air gun for suction and shooting a jet of compressed air. Therefore we has developed new air gun. In this paper we research for design and analysis of it. The air gun is composed of body, pipe, opening and shutting unit, turning unit, air tube and elements for fabrication. The developed air gun is experimented to confirm the efficiency.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.76-82
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• 1998

Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindle. Current work is emphasized on the investigation of the air jet effect on the protective collar type labyrinth seal. To improve the sealing capability of conventional labyrinth seal, air jet is injected against through the leakage flow. It has a combined geometry of a protective collar type and an air jet type. In this study, both of a numerical analysis by CFD(Computational Fluid Dynamics) and experimental measurements are carried out to verify sealing improvement. Both of the turbulence and the compressible flow model are introduced in CFD analysis. The sealing effect of the leakage clearance and the air jet magnitude are studied for various parameter in the experiment. The results of pressure drop in the experiment match reasonably to those of the simulation by introducing a flow coefficient. Effects of sealing improvement are explained as decreasing of effective leakage clearance by air jetting. Thus, sealing effect is improved by amount of air jetting even though clearance becomes larger.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.625-629
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• 1997

Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindele. Current work was emphased on the investigation of air jet effect on the protective collar type labyrinth seal. To improve the sealing capability of conventional labyrinth seal,ari jet was injected against through the leakage flow. It has a combined geometry of a protective collar type and an air jet type. In this study, both of a numerical analysis by CFD (Computational Fluid Dynamics) and experimental measureements are carried out of verify sealing improvement. But of the turbulence and the compressible flow model were introduced in CFD analysis. The sealing effect of the leakage clearance and the air jet magnitude were studied for variousparameter in the experiment. The results of pressure drop in the experiment match reasonably to those of the simulation by introducing a flow coefficient. Effects of sealing improvement are explained as decreasing of effective leckage clearance by air jetting. Thus, sealing effect is improved by amount of air jetting even though clearance become larger.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3021-3031
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• 1994

Experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and drop sizes were measured at each injection pressure condition for different mixing port length. The air flow rate was almost unaffected by the change of the mixing port length. However, the water flow rate was relatively susceptible to the change of the mixing port length. The mixing point pressure was very much influenced by the mixing port length. Variations of spatial distribution of Sauter Mean Diameter (SMD, $D_{32}$) and the cross-section-averaged SMD ($D_{32,m}$) with different mixing port length and air/water mass flow rate ratio were examined. Generally, when the mixing port length was reduced, the mean drop size decreased and became spatially even.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.768-773
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• 2004

When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is underexpanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with nonequilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics can not even know. In the present study, the effect of the nonequilibrium condensation on the underexpanded moist air jet impinging on a vertical flat plate is investigated experimentally. Flow visualization and impact pressure measurement are performed for various relative humidities and flat plate positions. The obtained results show the plate shock and Mach disk are dependent on the nozzle pressure ratio and the relative humidity, but for a given nozzle pressure ratio, the diameters of the plate shock and Mach disk depend on the stagnation relative humidity. The impact pressure deviation from the flow of without condensation is large, as the relative stagnation humidity increases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1390-1398
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• 1988

The purpose of this study was experimentally to investigate the disintegration process and disintegration mechanism when co-axial air flows vertically for the longest smooth liquid jet. These were affected by liquid velocity, air velocity, air-to-liquid diameter ratio, nozzle shape, and air-liquid contacting position. That is, this process of disintegration of the liquid jet was similar to that occurred when liquid pressure was increased. At Reynolds number of 10, 000 and below, the changes in the breakup length represent different tendency according to liquid flow rate. The influence of air flow on the disintegration of liquid jet was different according to air-to-liquid diameter ratio, air orifice diameter, nozzle shape and contacting position of liquid and air. In particular, when the tip of liquid nozzle was inside the air orifice, the effect of air flow was the larger than outside the air orifice. The effect of liquid mass flow rate on the change rate of the breakup length was also different.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.242-245
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• 2009

The effect of fuel composition on flame length was studied in a non-premixed turbulent diluted hydrogen jet with coaxial air. The observed flame length was expressed as a function of the ratio of coaxial air to fuel jet velocity and compared with a theoretical prediction based on the velocity ratio. Four cases of fuel mixed by volume were determined. In the present study, we derived a scaling correlation for predicting the flame length in a simple jet with coaxial air using the effective jet diameter in the near-field concept. The experimental results showed that visible flame length had a good relation with the theoretical prediction. The scaling analysis is also valid for diluted hydrogen jet flames with varied fuel composition.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.1
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• pp.51-59
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• 1994

The gas jet pumps serve to preduce a vacuum or can be used as gas jet compressors. These are operated on the same principle as a steam jet vacuum pump : in the driving nozzle the pressure energy of the motive medium is converted into the kinetic energy. In the diffuser the driving jet mixes with the suction medium and the kinetic energy is reconverted into the pressure enegy. The application fields of gas jet ejectors are the evacuation of siphoning installations, the elevation of liquids, the production of vacuum filters, the vacuum supporting airlift system, the evacuation of the suction line of centrifugal pumps and the ventilation of the dangerous gases to the atmosphere. The performance of gas jet ejector is influenced strongly to velocity coefficient of motive nozzle, the distance between the motive outlet to the diffuser inlet and the dimensions of diffuser. This study is performed for the computer aided design of gas jet ejectors in future. Through the present experiments, it is known that the velocity coefficient of the motive air nozzle ranges from 0.91 to 0.95 and the maximum efficiency of gas jet ejector is 24.6%.