• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1613-1620
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• 1990

For the purpose of the study on the spray characteristics of a coaxial nozzle, the measurement of the velocity and size of droplets, concentration, and the statistical correlation coefficient between the fluctuation of the velocity and that of the corresponding drop diameter have been carried out. Various method of simultaneous measurement of velocity and drop size have been developed from LDV techniques. The technique used here belongs to the method that supposed by Yule, Holve and Self. It has the advantages of making use of a standard LDV apparatus to which minor modifications have been brought, photomultiplier is equipped with a slit instead of a pinhole and observed the measuring volume at an angle of 90.deg.. The voltage supplied by the photomultiplier has undergone an appropriate analog and digital processing. The experimental results give a good idea of the two phase flow organization and can be helpful to find a drop diffusion model when suitable data are imput.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.169-173
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• 2007

Slit-coater nozzle is one of core equipments of coating process in LCD panel manufactory. As a glass substrate size become bigger, a nozzle performance and a high-speed coating process are considered important issues. To design the optimal nozzle, the characteristics of fluid inside nozzle are studied using CFD (Computational Fluid Dynamics) method. Through research on design factors, we can know the coating uniformity influenced by lip length, cavity angle and gap size. The future work for this study is to find the factors in high-speed coating process and function between factors of design.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.153-157
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• 2001

Operation conditions for the generation of an HF laser driven by fluorine-hydrogen combustion were discussed by mc:asuring the intensities of excited HF* molecules. Optimum injection quantities of fluorine gas for the generation of fluorine atoms was two times the injection mole number of hydrogen fuel. Slit nozzles with two dimensional configuration were used for the production of excited HF* molecules. When the injection mole number of secondary hydrogen gas is 1.3 times the injection mole number of fluorine gas, the fluorescence intensities of excited HF* molecules show maximum values. alues.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.9-16
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• 2016

An experimental study was performed to investigate the combustion characteristics of the liquid hydrocarbon fuel atomized by an ultrasonic oscillator. Configuration of the flame was caught by the high-speed camera, and images were analyzed in detail through a post-processing. In addition, the fuel consumption was measured using the balance during the combustion reaction. As a result, the consumption of atomized fuel increased with the increasing flow-rate of carrier-gas, but any correlation between the air/fuel ratio and carrier-gas flow-rate was not found. The variation of flame area was dependent on the fuel consumption and input power of the ultrasonic oscillator. FFT (Fast Fourier Transform) analyses using the flame area were conducted in order to discuss flame flickering.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.1-8
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• 2023

A study was conducted to scrutinize the behavior of the ultrasonically-atomized kerosene lifted-flame according to the carrier gas flow-rate and position of ultrasonic standing wave (USW). The combustion region of the kerosene-aerosol generated through a slit-jet nozzle was visualized using a DSLR, ICCD, high-speed camera, and Schlieren technique, and the fuel consumption was measured by using a precision balance. As a result, the flame was confined within the region bounded by the USW-field, and the fuel consumption decreased as the position of the USW field increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.285-291
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• 2012

A lot of research on the stability of nonpremixed flames has focused on the fuel-nozzle and quarl geometries. Of the work carried out, only a small amount has focused on the stability of the nonpremixed flame according to the recession distance and air-nozzle geometry. Therefore, in this study, a coaxial-diffusion-type gas burner with a swirler is designed for the systematic investigation of the combustion characteristics of a $CH_4$ flame depending on the recession distance and secondary air-nozzle geometry. 1st air is flowed through the swirler, and 2nd air is flowed through each nozzle. It is shown that the secondary air velocity greatly influences the flame length and shape. There is an optimum recession distance for each nozzle for the best combustion efficiency. In this study, it is shown that the optimized recession distance is nearly half the outer diameter of the air-supply nozzle.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.19-25
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• 2023

With an attempt to investigate the correlation between the internal pressure distribution of slit nozzle and the thickness uniformity of slot-coated thin films, we have performed computational fluid dynamics (CFD) simulations of slit nozzles and slot coating of high-viscosity (4,800 cPs) polydimethylsiloxane (PDMS) using a gantry slot-die coater. We have calculated the coefficient of variation (CV) to quantify the pressure and velocity distributions inside the slit nozzle and the thickness non-uniformity of slot-coated PDMS films. The pressure distribution inside the cavity and the velocity distribution at the outlet are analyzed by varying the shim thickness and flow rate. We have shown that the cavity pressure uniformity and film thickness uniformity are enhanced by reducing the shim thickness. It is addressed that the CV value of the cavity pressure that can ensure the thickness non-uniformity of less than 5% is equal to and less than 1%, which is achievable with the shim thickness of 150 ㎛. It is also found that as the flow rate increases, the average cavity pressure is increased with the CV value of the pressure unchanged and the maximum coating speed is increased. As the shim thickness is reduced, however, the maximum coating speed and flow rate decrease. The highly uniform PDMS films shows the tensile strain as high as 180%, which can be used as a stretchable substrate.