• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.116-124
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• 2007

An optical method to measure the size and number density of soot aggregates in diesel exhaust has been proposed in this study. Two laser beams in co-axial alignment transmit a soot loaded exhaust gas flow, and the transmittance at each wavelength is detected by a photo diode simultaneously. The volume equivalent diameter and number density of soot aggregates in the optical path can be theoretically given by the transmittance values measured at two wavelengths. A test conducted by a single cylinder, 4 cycle, small and DI diesel engine shows that the temporal variations of the size and number density of soot aggregates in the diesel exhaust can be measured by the proposed method at a transient mode operation. It is found that the volume equivalent diameter varied temporally from 70 to 110 nm during the period that high soot concentration is observed. One can also conclude that the optical length longer than 1 m in the dynamic range regarding this method is preferable for measuring soot concentration at the level of $1\;mg/m^3$.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.179-188
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• 2003

The spray characteristics of dual orifice injector were investigated under two different fuels through measurement of SMD, number density and volume flux by using PDPA system. In this experiment, we found out that the droplet size and spray structure are strongly depend on fuel density and viscosity.

• Journal of ILASS-Korea
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• v.8 no.2
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• pp.7-15
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• 2003

The effects of fuel density and fuel viscosity on spray characteristics were investigated under two different gas turbine fuels and various fuel supply pressure conditions through measurement of SMD, number density and volume flux by using PDPA system in dual orifice injector for gas turbine engines. In this study, we found out that the droplet size and spray structure are strongly depend on fuel density for dual orifice injector. The spray characteristics of high density fuel in dual orifice injector are similar with the characteristics of low density fuel in single orifice injector. The shear region between primary main fuel stream and secondary main fuel stream is examined in low density fuel condition but not exist in high density fuel condition, then this shear region is very important in quality of gas turbine spray. There are worth consideration for the effect of fuel density on spray characteristics in frontal device design to improve combustion efficiency.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.11-22
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• 1994

The pupose of this study is to measure droplet size and velocity simultaneously for a transient diesel fuel spray in a quiescent chamber at atmospheric temperature and pressure. Generally, diesel combustion phenomena is mainly governed by characteristics of injection system and fuel spray. Therefore we need to clarify these characteristics for developing more economical diesel systems. In this study, correlation between droplet size and velocity was measured at downstream distance from nozzle. Governing parameters are pump speed and fuel quantity for the detailed nature in this transient diesel fuel spray. It is observed effect to the droplet size and velocity distribution. Velocity(peak, mean, rms), number density and droplet size were investigated simulaneously using PDA in the spray. Various results are presented to illustrate the effects of operation factors and correlation between the droplet diameter and velocity.

• Fire Science and Engineering
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• v.30 no.2
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• pp.62-67
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• 2016

In this study, the optical depth is analyzed with the effects of droplet size distribution of the water curtain nozzle to attenuate the radiative heat transfer. The HELOS/VARIO equipment is used for the measurement of the droplet size distributions. The spray characteristics are quantified by the investigation of Deirmenjian's modified gamma distribution function. The distribution constant of the nozzle can be obtained as ${\alpha}=1$ and ${\gamma}=5.2$. The generalized equation of the optical depth related with the droplet size distribution is introduced. These results will be applicable to the analysis of the design condition of the water curtain nozzle.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.1-7
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• 2019

Electromagnetic measurements of the power cable tunnel were conducted from August 10 to 20, 2018, in the ${\bigcirc}{\bigcirc}$ city underground utility tunnel. During this period, the average temperature was $31.89^{\circ}C$ and the humidity was 67.56% in power cable tunnel. As a result of the electromagnetic measurement, the highest electric field was 25.3 V/m and the magnetic flux density was $42.6{\mu}T$. The average electric field was 18.56 V/m and the magnetic flux density was $29.32{\mu}T$ in the power cable tunnel. As a result of comparison with the electric equipment technical standard, the electric field in the power cable tunnel was 0.5% of the electric equipment standard and 35.2% of the magnetic flux density. It's similar value that electric field is about robotic vacuum(15.53 V/m), and magnetic flux density is similar value about capsule- type coffee machine ($23.07{\mu}T$). The number of cable lines and the size of the electromagnetic waves were not proportional to each other through comparison of cable lines in the power cable tunnel. It was confirmed that 154 kV, rather than 22.9 kV, could have a greater influence on occupational.

• Journal of ILASS-Korea
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• v.1 no.3
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• pp.51-59
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• 1996

An experiment was carried out on the structure of twin spray from pressurize-swirl nozzles, in order to investigate the effect of different size of spray nozzles on the characteristics of the overlap of two single sprays, for example, mean diameter, number density, and spatial distribution of flow rate. Using image processing method, the distributions of size and velocity of droplets of a single spray and twin spray were measured and compared to investigate the overlapping effect of two identical sprays. Comparing experimental results from a twin-spray with those from two-single sprays shows that the flow rate distribution of the twin-spray was concentrated around the midst of the overlapping region of two sprays. In this region, Sauter mean diameter (SMD) did not change much in the twin spray from 6032 nozzles, but it was smaller by 10 micrometers in the twin-spray than two-single sprays from 60063 nozzles. In spite of large difference in Weber numbers of the colliding sprays between the 60063 and 6032 nozzles, the phenomena did not have a big change in the overlapping region of twin spray. This shows that in the collision between droplets from two single spray in the overlapping region to cause the disruption of droplets, the size distribution of spray droplets was also important as well as Weber number.

• Particle and aerosol research
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• v.9 no.2
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• pp.39-50
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• 2013

Real-time aerosol measuring instruments have been widely used for the measurement of atmospheric aerosol, diesel particulate matter, or material synthesis. A scanning mobility particle sizer (SMPS) measures the number size distribution of particles using electrical mobility detection technique. An aerodynamic particle sizer (APS) is used to determine the number concentration and the mean aerodynamic diameter of test particles. An electrical low-pressure impactor (ELPI) is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. In this study, the performance of these instruments were evaluated to assess their ability to obtain mass concentrations from particle number concentration measurements made as a function of particle size. The effect of determination of particle density on the measurement of mass concentration was investigated for the three instruments.

• Analytical Science and Technology
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• v.8 no.4
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• pp.411-418
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• 1995

A method for the direct determination of elemental content in each of aerosol particles by inductively coupled plasma atomic emission (ICP-AES) or mass spectrometry (ICP-MS) is described. This method is based upon the introduction of diluted aerosol into an ICP and the measurement of either the flash emission intensities of an atomic spectral line or ion intensities. A pulse-height analyzer is used for the measurement of the distribution of the elemental content. In order to calibrate the measuring system, monodisperse aerosols are used. The potentials of the method are shown by demonstrating the copper emission signals from the aerosols generated at a small electric switch, a study of the relation between the decreasing rate of particle number density and particle size, and measurements of calcium contents in the individual biological cells.

• Journal of the Korean institute of surface engineering
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• v.48 no.4
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• pp.131-135
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• 2015

We investigated the surface morphology and the change of Ag concentration for SnAg electrodeposits according to the current density using labmade and commercial plating solutions. The concentration of Ag in the SnAg electrodeposits decreased with increasing the current density. The Ag concentrations at the conditions of over $50mA/cm^2$ were below 3 wt% and the surface was relatively smooth. Cu pillar bump was fabricated by using SnAg electroplating, and it was reflowed at $240^{\circ}C$ for 90 sec. The cross-sectional microstructure was investigated by using EBSD measurement and it was found that the grain size of SnAg became smaller by increasing the number of reflow treatments.