• Journal of ILASS-Korea
• /
• v.9 no.4
• /
• pp.17-23
• /
• 2004

Spray characteristics of a twin-hole air shrouded nonle designed for gasoline injectors was investigated by using laser diffraction particle analyzer (LDPA) and tomography reconstruction- A confined spray chamber which is optically accessible through a pair of glass windows was made to simulate the fuel injection condition in intake manifold of gasoline engine. The measurement was applied to the twin hole injector with and without an air shroud. It demonstrates that for the case with an air shroud, fine atomization is achieved and there exists a large number of fine droplets between the region of the main spray streams, which conforms with the spray visualization. The drop size distribution was investigated as a function of elapse time after fuel injection. The distribution was greatly affected by the measurement position from the injector exit. Also, the spatially resolved spray volume fraction and Sauter Mean Diameter (SMD) from line-of-sight data of the LDPA are tomographically reconstructed by Convolution Fourier transformation under the steady injection condition.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.2
• /
• pp.467-474
• /
• 2017

Each river confluence has the inherent hydraulic and mixing characteristics coming from its bathymetry and topography. It is necessary to make the measurement covering the spatial extent of studying area in order to catch these 2-dimensional intrinsic characteristics. This study focuses to investigate the hydraulic and mixing characteristics at the confluence of Nakdong and Geumho River, from field measurement of flow, water quality, and suspended particle distribution with ADCP (Riversurveyor M9), multi-parameter water quality sonde (YSI6600V2), and submersible system for in-situ observations of particle size distribution and volume concentration (LISST : Laser In-Situ Scattering & Transmissometry), respectively. From the results, it can be found that the field measurement of suspended particle and water quality distribution can be the useful approach to catch the hydraulic and mixing characteristics at a river confluence.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.269-272
• /
• 1999

It is still hard to measure the strain distribution over entire surface of a medium or large-size stamped part even by using an automated strain measurement system. Several methods which enable to enlarge the measurement range without losing accuracy and precision are suggested in this study, The superposition of images having different high-lightened or damaged part each other results in an enhanced image. A new method for constructing the element connectivity from a line-thinned image makes it possible to identify up to 1,000 elements. And the geometry assembling algorithm is proved very efficient in which the whole area to be measured is divided into several parts ; the coordinate transformation between every two adjacent parts is obtained from the concept of the least square error ; and the 3-D shape or strain distribution over the whole surface is assembled,

• Journal of Korean Society for Atmospheric Environment
• /
• v.15 no.E
• /
• pp.73-79
• /
• 1999

To Characterize the single raindrops as a function of their size we designed the sampling and handling apparatuses. Samplings of single and size- classified raindrops were performed at a height of 20m above the ground level of a Kyoto University building located in Uji, Japan in rain events from middle of July to the end of August, 1999. And PIXE method was applied to the analysis of single raindrops sampled as a function of their size. Diameter change of frozen raindrops by liquid nitrogen did nto affect the size segregation ability of our sampling apparatus. The number of raindrops increases with decreasing drop size. And it is found that the size distribution of raindrops verified depends on the rain events. Application of PIXE analysis to the measurement of single raindrops was very successful. Every element showed a continuous increase in concentration with decreasing raindrop diameter. It seems reasonable to say that our work should be helpful to obtain more detailed information on single raindrops and especially to study on the rainout and washout mechanisms.

• Journal of environmental and Sanitary engineering
• /
• v.17 no.2
• /
• pp.11-17
• /
• 2002

Diesel particulate matter (DPM) is known to be one of the major harmful emissions produced by diesel engines. The majority of diesel particles are in the range of smaller than $I{\mu}\textrm{m}$. Because of their tiny volume, ultrafine diesel particles contribute very little to the total mass concentration which is currently regulated for automobile emissions. Diesel particles are known to have deleterious effects upon human health because they penetrate human respiratory tract and have negative effects on the health. The measurement of the number distribution of nanometer size particles (nanoparticles) in the diesel exhaust emission is important in order to evaluate their environmental and health impact, and to develop new types of diesel particulate filters. In this study, we directly sampled particulate matters emitted from a diesel truck mounted on the chassis dynamometer by a flow separator and dilution system, and measured the nanoparticles using two types of differential mobility analyzers combined with a Faraday cup electrometer (FCE) and a condensation particle counter (CPC). The particle size distributions were analyzed by changing engine operation condition, i.e. ratio of engine loading. The total number concentration of particles were increased with the engine loading ratio and the nanoparticles (less than 50nm) were affected by hydrocarbon (HC) concentration in the diesel exhaust.

• Particle and aerosol research
• /
• v.5 no.4
• /
• pp.179-188
• /
• 2009

The dry deposition fluxes of particulate polychlorinated biphenyls (PCBs) were measured along with their mass size distributions at Seoul and Incheon in fall in 1999. The dry deposition fluxes of PCBs were in the range of $16.7{\sim}62.2ng/m^2/day$. The ambient concentrations of particulate PCBs were in the range of 0.07 to $0.20ng/m^3$. Generally, the mass size distribution of particulate PCBs shows bi-modal distribution. The mass fraction of PCBs in the fine particle fraction ($D_p<2.1 {\mu}m$) was over than 55% of the total PCBs concentrations. It was found that Seoul and Incheon were not the major source of PCBs emissions in Korea. Based on the comparison with the measurement data in summer, 1999, it is likely that both the dry deposition fluxes and ambient particulate PCBs concentrations were not site-specific.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.12
• /
• pp.1691-1701
• /
• 1998

Fly ash produced in coal combustion is a fine-grained material consisting mostly of spherical, glassy, and porous particles. A study on the formation mechanism of the fly ash from coal particles in the pulverized coal power plant is investigated with a physical, morphological, and chemical characteristic analysis of fly ash collected from the Samchonpo power plant. This study may contribute to the data base of domestic fly ash, the improvement of combustion efficiency, fouling phenomena and ash collection in the electrostatic precipitator. The physical property of fly ash is determined using a particle counter for the measurement of ash size distribution. Morphological characteristic of fly ash is performed using a scanning electron micrograph. The chemical components of fly ash are determined using an inductively coupled plasma emission spectrometry(ICP). The distribution of fly ash size was bi-modal and ranged from 12 to $19{\mu}m$ in mass median diameter. Exposure conditions of flue gas temperature and duration within the combustion zone of the boiler played an important role on the morphological properties of the fly ash such as shape, particle size and chemical components. The evolution of ash formation during pulverized coal combustion has revealed three major mechanisms by large particle formation due to break-up process, gas to particle conversion and growth by coagulation and agglomeration.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.4
• /
• pp.689-696
• /
• 1989

In this experimental study, relative particle size distribution was measureed at the inlet and outlet of the slit impactor using the particle sizer. The imployed measuring method of the size distribution was different from the conventional method. This measurement system has the advantage of obtaining the particle collection efficiency for various particle size easily and at once compared with other methods. The effects of jet to plate distance and Reynolds number on the characteristic impactor efficiency curves have been studied. In the results of this experiment, the increment of collection efficiency was observed as Reynolds number increases in the case of S/W = 1/2 but was very slight. The influence of S/W is more remarkable than that of Reynolds number on the particle collection efficiency.

• International Journal of Automotive Technology
• /
• v.2 no.4
• /
• pp.165-170
• /
• 2001

This study is focussed on the investigation of spray characteristics from the high pressure gasoline injector for the application of gasoline direct injection engine. For the analysis of spray structure of high pressure gasoline injector; the laser scattering method with a Nd-Yag laser and the Phase Doppler particle analyzer system were applied to observe the spray development and the measurement of the droplet size and velocity of the spray, respectively. Also spatial velocity distribution of the spray droplet was measured by use of the particle image velocity system. Experimental results show that high pressure gasoline injector shapes the hollow-cone spray, and produce the upward ring shaped vortex on the spray surface region. This upward ring shaped vortex promotes the secondary atomization of fuel droplets and contributes to a uniform distribution of fuel droplets. Most of fuel droplets are distributed under 31$\mu m$ of the mean droplet size (SMD) and the frequency distribution of the droplet size under 25$\mu m$ is over 95% at 7 MPa of injection pressure. According to the experimental results of PIV system, the flow patterns of the droplets velocity distribution in spray region are in good agreement with the spray macroscopic behaviors obtained from the visualization investigation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.6
• /
• pp.753-759
• /
• 2000

Photoelectric charging is a very efficient way of charging small particles. This method can be applied to combustion measurement, electrostatic precipitator, metal separation and control of micro-contamination. To understand the photoelectric charging mechanism, particle charging of silver by exposure to ultraviolet is investigated in this study. Average charges and charge distributions are measured at various conditions, using two differential mobility analyzers, a condensation nucleus counter, and an aerosol electrometer. The silver particles are generated in a spark discharge aerosol generator. After that process, the generated particles are charged in the photoelectric charger using low-pressure mercury lamp that emits ultraviolet having wavelength 253.7 nm. The results show that ultra-fine particles are highly charged by the photoelectric charging. The average charges linearly increase with increasing particle size and the charge distribution change with particle size. These results are discussed by comparison with previous experiments and proposed equations. It is assumed that the coefficient of electron emission probability is affected by initial charge. The results also show that the charge distribution of a particle is dependent on initial charge. Single changed particle, uncharged particle and neutralized particle are compared. The differences of charge distribution in each case increase with increasing particle size.