• Journal of the Korean Society of Visualization
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• v.3 no.1
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• pp.71-77
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• 2005

Information on temporal evolution of whole velocity fields are essential for physical understanding of a complicated turbulent flow. Due to advances of high-speed imaging technique, laser and electronics, high-speed digital cameras and high-repetition pulse lasers are commercially available in nowadays. A dynamic PIV system that can measure consecutive instantaneous velocity field with 1K$\times$ 1K pixels resolution at 1 fps was developed. It consists of a high-speed CMOS camera and a high-repetition Nd:YLF pulse laser. Theoretically, it can capture velocity fields at 20 fps with a reduced spatial resolution. In order to validate its performance, the dynamic PIV system was applied to a turbulent jet of which Reynolds number is about 3000. The particle images of 1024$\times$512 pixels were captured at a sampling rate of 4 KHz. The dynamic PIV system measured successfully the temporal evolution of instantaneous velocity fields of the turbulent jet, from which spectral analysis of turbulent structure was also feasible.

• Journal of Environmental Science International
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• v.32 no.9
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• pp.659-669
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• 2023

The purpose of this study is to predict the pressure drop due to the installation of venturi under diverse operating conditions such as dust concentration, pulse interval and pressure, and filtration velocity using algebraic-linear regression model and use it as an economic data and efficient operating condition for a pulse air jet bag filter. A pilot scale bag filter with a filter a filter size(Ø140 × 850ℓ, 12) was used, and the filters used in the experiment were the polyester filters most commonly used in real industrial sites. The SAS 9.4 program (SAS Institute, USA) was used to predict and to determine the effects of inlet concentration (C_i), pulse interval (P_i) and pressure (P_p), filtration velocity (V_f), presence or absence of venturi, etc. The results are shown below. The variation in pressure drop with or without venturi installation was 38.8 mmAq when venturi is installed and 47.6 mmAq when venturi is not installed, indicating a difference in pressure drop of 8.8 mmAq depending on venturi installation. It is estimated that the efficiency can be improved by about 18.5% if the venturi is installed.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.20-24
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• 2010

High speed cutting processes of rigid flexible printed circuit board by making use of high power UV laser with nano-second pulse width have been proposed and investigated experimentally. Also robust laser cutting system has been designed and developed in order to obtain a good cutting quality of rigid and flexible PCB with multi-layers (2-6 layers). Power controller module developed for ourselves is adapted to control the laser output power in the range less than 1%. The systems show the good performance of cutting speed, cutting width and cutting accuracy, respectively. Especially we have confirmed that the short circuit problem due to the carbonized contamination occurred in cross section of multi-layers by thermal effect of high power laser has been improved largely by using multi-pass cutting process with low power and high speed.

• Journal of Environmental Science International
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• v.20 no.1
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• pp.25-34
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• 2011

The new empirical static model was constructed on the basis of dimension analysis to predict the pressure drop according to the operating conditions. The empirical static model consists of the initial pressure drop term (${\Delta}P_{initial}$) and the dust mass number term($N_{dust}=\frac{{\omega}_0{\nu}_f}{P_{pulse}t}$), and two parameters (dust deposit resistance and exponent of dust mass number) have been estimated from experimental data. The optimum injection distance was identified in the 64 experimental data at the fixed filtration velocity and pulse pressure. The dust deposit resistance ($K_d$), one of the empirical static model parameters got the minimum value at d=0.11m, at which the total pressure drop was minimized. The exponent of dust mass number was interpreted as the elasticity of pressure drop to the dust mass number. The elasticity of the unimodal behavior had also a maximum value at d=0.11m, at which the pressure drop increased most rapidly with the dust mass number. Additionally, the correlation coefficient for the new empirical static model was 0.914.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.04a
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• pp.41-41
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• 1999

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2004.11a
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• pp.32-35
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• 2004

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.623-625
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• 2004

In Electro-Luminescence Display making process, it is necessary to do high molecule patterning effectively. Recently, one of the most effective way is the patterning method using Ink-Jet head controller. To maximize the effect, it is needed to control each channel of Ink-Jet head and develop that controller. Thus, we implement the Ink-Jet Head Controller which can control the parameters of 128 fire pulses independently, improve the accuracy of patterns more than 100 times previous ones, and apply random patterns.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.223-232
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• 2004

The change of pressure drop according to the change in the inlet concentration, pulse interval, and injection distance of pulse air jet type bag filters, and the effect of venturi installation are as follows. The pressure drop with the range of 30 to $50mmH_2O$ varies according to the injection distance with 30, 50, 70, 90sec and the inlet concentration of venture built-in fabric filters. For the lower concentration of 0.5g/㎥ and 1g/㎥, the pressure $drop(\DeltaP)$ was stable 60 to 90minutes after operation. For the higher concentration of 3g/㎥, as $\DeltaP$ continues to go up, pulse interval should be set shorter than 30 seconds. The pressure drop with the injection distance of 1l0mm, when inlet dust concentration is 0.5g/㎥ or 1g/㎥, is 1.3 to 2 lower than with the injection distance of 50, 160, and 220mm, which means that the inflow amount of the secondary air by the instant acceleration is large. The injection distance of 2g/㎥ and 3g/㎥ has the similar pressure distribution. The higher inlet concentration is, the more important pulse interval is than injection distance. The pressure drop has proved to be larger when inlet concentration is lower and injection distance closer, on condition that the venturi is installed. The change in the pressure drop was smallest when injection distance was 50mm, followed by 220mm, 160mm, and 110mm.

• Journal of Environmental Science International
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• v.16 no.4
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• pp.449-458
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• 2007

Research results for the pressure drop variance depending on operation conditions such as change of inlet concentration, pulse interval, and face velocity, etc., in a pulse air jet-type bag filter show that while at $3kg/cm^2$ whose pulse pressure is low, it is good to make an pulse interval longer in order to form the first layer, it may not be applicable to industry because of a rapid increase in pressure. In addition, the change of inlet concentration contributes more to the increase of pressure drop than the pulse interval does. In order to reduce operation costs by minimizing filter drag of a filter bag at pulse pressure $5kg/cm^2$, the dust concentration should be minimized, and when the inlet dust loading is a lower concentration, the pulse interval in the operation should be less than 70 sec, but when inlet dust loading is a higher concentration, the pulse interval should be below 30 sec. In particular, in the case that inlet dust loading is a higher concentration, a high-pressure distribution is observed regardless of pulse pressure. This is because dust is accumulated continuously in the filter bag and makes it thicker as filtration time increases, and thus the pulse interval should be set to below 30 sec. If the equipment is operated at 1m/min of face velocity, while pressure drop is low, the bag filter becomes larger and thus, its economics are very low due to a large initial investment. Therefore, a face velocity of around 1.5 m/min is considered to be the optimal operation condition. At 1.5 m/min considered to be the most economical face velocity, if the pulse interval increases, since the amount of variation in filter drag is large, depending on the amount of inlet dust loading, the operation may be possible at a lower concentration when the pulse interval is 70 sec. However, for a higher concentration, either face velocity or pulse interval should be reduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.886-891
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• 2008

This experimental investigation is concerned with the relationship between the electrical-on time of a solenoid which is located on the top of a pulse valve and air consumption of a dust collector. For the air consumption per pulse would be one of major factors affecting the operating cost of a dust collector, more attention is needed on the behaviour of a pulse valve. A pulse jet is blasted into a bag filter as the diaphragm valve opens and inflates a bag filter. This air-blast breaks up the dust layer and cleans the filter by dislodging dust cake. It is interpreted in this research that the cleaning filter is done by the impulse of a pulse jet. Hence, the magnitude and fluctuation of the dynamic pressure is measured using by a dynamic pressure sensor and the impulse is obtained by integrating dynamic pressure variation against time. Through this experimental work, conclusions are drawn implementing magnitude of averaged impulsive pressure per pulse or pressure impulse per unit volume of consumed air.