• Proceedings of the KSME Conference
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• 2001.06d
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• pp.596-599
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• 2001

Recently, as the environmental pollution becomes an important issue, aerosols which are the main components of the atmospheric pollution become the subject of a lot of researches. An impactor is a kind of sampling and measuring equipment for aerosols since 1970s. The impactor uses coating materials to obtain high performance. However, there are a lot of situations when coating materials are not available and in this case the classification efficiency of the impactor decreases significantly. In this study, the impaction plate of the impactor is cooled, therefore the impactor performs efficiently when coating materials are not available.

• Journal of Auto-vehicle Safety Association
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• v.6 no.2
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• pp.43-48
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• 2014

The flexible pedestrian legform impactor(Flex-PLI) consisting of a flexible femur and tibia will be tested for pedestrian protection by global technical regulation(GTR) within the next couple of years as a replacement for the existing transport research laboratory(TRL) legform impactor. In this study, a computer aided engineering(CAE) model was used to perform the effect analysis of each injury with regard to the changes in tolerance factors with the baseline results without tolerance. The tolerance factors were the height of impactor from ground reference line, initial velocity of impactor and rotation of impactor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.349-358
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• 2004

A low pressure impactor is an impaction device to separate airborne particles into aerodynamic size classes at low pressure condition. We designed a two-stage low-pressure impactor to classify submicron sized environmental aerosols. Performance evaluation was carried out for stages 1 and 2 by using an electrical method. Monodisperse liquid dioctyl sebacate (DOS) particles were generated using evaporation-condensation process followed by electrostatic classification using a DMA (differential mobility analyzer). The test particles were in the range of 0.08∼0.8$\mu\textrm{m}$. For the evaluation of the impactor we used two electrometers; one was connected to the impaction plate of the impactor and the other was to the Faraday cage used as a backup filter. The effect of polydispersity of test aerosols on the performance was investigated. The results showed that the experimental 50-% cutoff diameters at each impactor's operation pressure were 0.53 and 0.187$\mu\textrm{m}$ for stages 1 and stage 2, respectively. The effects of operation pressure on the cutoff diameter and the steepness of collection efficiency curves were also investigated.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1417-1422
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• 2003

An electrical cascade impactor is a multistage impaction device to separate airborne particles into aerodynamic size classes using electrical method. We designed a real-time three-stage electrical low-pressure impactor, which is proper to nanometer sized environmental aerosols. Performance evaluation was carried out for stage 1 and 2. The monodisperse liquid dioctyl sebacate (DOS) particles were generated using condensation-evaporation followed by electrostatic classification using DMA (differential mobility analizer) for particles with diameters in the range of $0.04{\sim}0.8{\mu}m$. The evaluation of the electrical impactor is based on the use of two electrometers, one connected to the impaction plate of the impactor, and the other to the faraday cage as backup filter. The results showed that the experimental 50% cutoff diameters in the operation pressure were 0.53 and $0.12{\mu}m$ for stage 1 and stage 2. The effect of operation pressure on the cutoff diameter and the steepness of collection effcieicy curves is investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.7
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• pp.826-833
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• 2004

Cascade impactors are widely used to collect size classified aerosol. A major disadvantage of this instrument is the required long sampling time. Electrical low pressure impactor has been developed to overcome this disadvantage and to achieve real-time measurements on the particle size distribution. The instrument consists primarily of a corona charger, low pressure cascade impactor and multi channel electrometer. We designed and evaluated the performance of a potable 3-stage low pressure impactor using an electrical method. For the calibration of the impactor, monodispersed particles were generated using evaporation-condensation method followed by electrostatic classification using a DMA(Differential Mobility Analyzer). The collection efficiency curves of the stages can be determined by analysing the fraction of particles collected by each stage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.63-70
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• 2019

An electro-aerodynamic lens for improving the performance of virtual impactor has been proposed in this study. ANSYS FLUENT Release 16.1 was used for numerical analysis of virtual impactor with and without the electro-aerodynamic lens, used to collimate the incoming aerosol particles into a particle beam before injecting the particles into the virtual impactor. Particles supplied to the electro-aerodynamic lens were assumed to be highly charged. By using an aerodynamic lens before the virtual impactor, without any electrostatic effect, it was found that the cut-off diameter of the virtual impactor was reduced from $4.2{\mu}m$ to $0.68{\mu}m$ and that the fine particle contamination problem became more serious. However, by employing the combined electrostatic and aerodynamic effects, that is, by applying electric voltage potential to the electro-aerodynamic lens, the cut-off diameter was found to be further reduced to $0.45{\mu}m$ and the fine particle contamination was eliminated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.350.2-350
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• 2002

The purpose of this study was to present the possible use of a new standard impactor, the rubber ball (so-called, impact ball), and to assess its evaluation method as fur heavy-weight impact in multi-story residential buildings. Several experiments were carried out to investigate the effect of the impactor on noise propagation in reinforced concrete buildings. Then, the noise from the impact ball was psychoacoustically evaluated. (omitted)

• Journal of Environmental Health Sciences
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• v.33 no.2 s.95
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• pp.145-149
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• 2007

The range of reduction rates of airborne bacteria concentration at 6 hrs, 12 hrs, 24 hrs and 48 hrs, which means a storage time until input of agar media into incubator after air sampling with an impactor. were 15-20%, 25-40%, 35-50% and 55-70%, respectively, compared to initial concentration. Types of agar media and storage thermal condition did not significantly affect a collection efficiency of impactor in terms of evaluating airborne bacteria level (p>0.05). To better improve the impactor's collection efficiency of airborne bacteria, based on the result of this study, it is recommended that the vicinity of $25^{\circ}C$ should be sustained until input of agar media into incubator after air sampling.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.1
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• pp.67-76
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• 2003

Recently consideration of health and interest on bio aerosols have been growing steadily. In this study, inertial impactor, which can be used to collect airborne particles and bio aerosols, was newly devised for real-time observation on the particles collected on impaction plate. and named Visual Impactor. Flow field and particle trajectory in the space between nozzle and impaction plate was analyzed numerically, and the collection effciencies were calculated. Calibration and performance evaluation of the Visual Impactor was conducted with polydisperse aerosols generated from 0.1％ sodium chloride solution. Cut-off diameter from numerical simulation was in good agreement with that from experimental results. Because of particle bounce and particle deposition on nozzle tip due to short jet-to-plate distance, the collection efficiencies from numerical and experimental analyses were different slightly. Visual Impactor was used to collect airborne particles, and the features of collected particles could be seen in real-time. Airborne particles in different weather conditions (fine, cloudy, and rainy) were sampled and compared one another The features of collected airborne particles were dependent strongly upon relative humidity. In addition, with hours elapsing, shapes and colors of collected particles were changed by evaporation and surface tension, etc.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.E1
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• pp.9-16
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• 2001

To evaluate the correct separation capacity of cascade impactor for liquid aerosol, theoretical and experimental calculations of 50% cut-off diameter(ECOD(sub)50) were performed. A recalculation method of original diameter for hemispheric liquid aerosol collected on casecad impactor is also proposed newly using fixation technique. Calculated values for theoretical (ECOD(sub)50) of 40stage cascade impactor are 20, 6.4, 2.8, and 1.4$\mu\textrm{m}$ at 1st- ,2nd-, 3rd- and 4th-stage, respectively. A good agreement between the result of theoretical (ECOD(sub)50) and that og experimental ones was obtained at Stage 2 and 3. On the other hand, relatively large differences were found at Stage 1 and 4. Fixation for liquid aerosols using ${\alpha}$-cyanoacrylate monomer was performed successfully. The orignal diameter of liquid aerosols collected on each stage was calculated. The maximum levels of number size distribution curves at each stage are 19.8, 6.5, 3.1 and 1.5 $\mu\textrm{m}$ at 1st-, 2nd-, 3rd- and 4th-stage, respectively. The distortion of separation capacity of cascade impactor due to the split, merger, disappearance, and evaporation of liquid aerosols in the fluid did not occur.