• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.426-432
• /
• 2017

An experimental and numerical study on shock attenuation in a solid by a subminiature flyer impact was conducted to determine the performance of a subminiature exploding foil initiator such as, flyer velocity and impulse loading. The obtained attenuation pattern shows the possibility to determine the critical flyer velocity for initiating the miniaturized pyrotechnic unit by figuring out shock intensity and duration according to flight characteristics.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.27 no.2
• /
• pp.141-146
• /
• 1982

In the vine training methods, main vine training yield was 36% higher than the non-training. Main vine training date was studied for increasing cone yield in hops. Training was done four different dates from May 14 to May 29 including non-training as a check. Earlier training increased cone yield from 12 to 43% due to more beared branches per plant, longer branch length caused by accelerating the branch growth, and an increased of number of cone per beared branch and total cone number.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2008.04a
• /
• pp.308-312
• /
• 2008

In this study, we have carried out test to examine the ignition characteristics, such as a relation of moisture content and combustibility, and ignition temperature using KRS-RG-9000 tester, of significant part of above trees which are representative species of Young Dong Province of Korea. After rainfall, the percentage of moisture content of living leaves and branches was between 52 and 70%. But it was just between 17 and 33% after 144 hours drying at normal temperature. For dead leaves, it was 10% lower than of first. There was a significant difference on ignition characteristics. The hazard of ignition is highest on dead leaves. The ignition temperature of barks and branches is higher so a retard time is long than of living and dead leaves at normal temperature.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.5
• /
• pp.40-48
• /
• 2018

This paper presents a simulation-based design reliability estimation method of a low-energy exploding foil initiator (LEEFI) using a meta-model and describes the design reliability estimation results. The flyer velocity of the LEEFI is critical to initiate the explosive. Evaluation of the flyer velocity from mechanistic models in open literature requires a long computation time due to the multi-physical phenomena that generate the velocity. Moreover, the higher levels of confidence required for an initiator with high reliability incur higher computation costs. Thus, a meta-model of the flyer velocity over time was constructed in order to increase the computational efficiency for a reliable estimation. For different distributions and sigma levels of the design variables, the design reliability estimation results using the meta-model are provided. Additionally, the computational efficiency and accuracy of the estimation method are analyzed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2013.11a
• /
• pp.178-179
• /
• 2013

본 연구에서는 현재 사용되고 있는 건축물 내의 화장실 칸막이 재료를 대상으로 ISO 5660-1 콘칼로리미터(Cone calorimeter) 실험을 실시하여 대상 실험 재료들의 연소 특성을 비교 평가 하였다. 모두 5종류의 실험체를 사용하였으며, 화재 발생시 연소 중요 평가항목인 착화시간(Time to ignition), 총 방출열량(Total heat release), 최고 열방출율(Peak heat release rate), 평균 열방출율(Mean heat release rate)을 중점적으로 평가하였다. 실험결과, 착화시간은 일반 합판패널에서 빠르게 일어났으며, 총 방출열량, 최고 열방출율, 평균 열방출율은 고밀도 압축패널에서 높게 나타난 것으로 분석되었다.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.1
• /
• pp.17-24
• /
• 2004

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthened. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, it is well known that HCCI engines increased HC and CO. Thus, the investigation of combustion characteristics which consists cool and hot flames for HCCI engines were needed to obtain the optimal combustion condition. In this study, combustion characteristics for direct injection type HCCI engine such as quantity of cool flame and hot flame, ignition timing and ignition delay were investigated to clarify the effects of these parameters on performance. The results revealed that diesel combustion showed the two-stage ignition of cool flame and hot flame, the rate of cool flame increase and hot flame decrease with increasing intake air temperature. On the other hand, the gasoline combustion is the single-stage ignition and ignition timing is near the TDC. In addition mixed fuel combustion showed different phenomenon, which depends on the ratio of gasoline component. Ignition timing of mixed fuel is retarded near the TDC and the ignition delay is increased according to ratio of gasoline.

• Journal of Energy Engineering
• /
• v.25 no.3
• /
• pp.9-17
• /
• 2016

In this study, a method for CO reduction using char-coal combustions was developed with lignin and glycerin as combustion improvers. The relationship between CO emission and the combustion improvers was confirmed by measuring the CO concentration. The experiment to determine the combustion characteristics was conducted using glycerin, which shows high combustibility at low temperatures, impregnated with lignin, which has a specific surface area. The combustibility, volatility, and CO concentration were measured using thermo-gravimetric analysis(TGA), and gas chromatography-mass spectrometry(GC-MS). This study presents the optimal CO reduction ratio, which occurred when the combustible material contained a 20% blend of combustion improvers. This resulted in a 20-30% CO reduction rate compared to that achieved with normal char-coal.

• Fire Science and Engineering
• /
• v.26 no.3
• /
• pp.60-66
• /
• 2012

In this study, it was evaluated the fire risk during welding cutting tasks. Welding-cutting machines are representatively used at construction sites. Inverter AC/DC TIG welding macnine and inverter air plasma cutting machine were used in experiments. Temperature of spreaded cinders was measured using a thermal camera. Cinder sizes and spread range were measured according to the height and input current. It was also evaluated the fire risk during welding-cutting process, when flammable materials were located around the working area. There were used hay, dust fence, urethane foam, vinyl, paper and oil as flammable materials. Temperature of spreaded cinders was reached at about $450^{\circ}C$. Cinders were spread approximately 4.7 m, when a worker carried out cutting process at 2.5 m height. The possibility of a fire is very high, when flammable materials were located around the working area.

• Journal of Hydrogen and New Energy
• /
• v.22 no.6
• /
• pp.895-904
• /
• 2011

Stratified charge has been thought as one of the ways to avoid a sharp pressure rise on HCCI combustion. The purpose of this study is to evaluate the potential of stratified charge for reducing PRR on HCCI combustion. The pre-mixture with thermal, mixing and EGR stratifications is charged in Rapid Compression Machine. After that, the pre-mixture is compressed and in that process, in-cylinder gas pressure and temperature are analyzed. Additionally numerical calculation with multi-zones modeling is run to know the potential of stratified charge for reducing PRR.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.3
• /
• pp.81-87
• /
• 2009

In this study, we have investigated the combustibility of five shrubs growing in Youngdong area such as Lindera obtusiloba, Lespedeza maximowiczii, Zanthoxylum piperitum, Zanthoxylum schinifolium, and Corylus heterophylla var. thunbergii using the ignition temperature tester, the cone calorimeter and the smoke density chamber in order to estimate the danger of a forest fire. The results showed that Lespedeza maximowiczii has the lowest ignition temperature, the fastest ignition time and the highest average release concentrations of CO and $CO_2$. Zanthoxylum piperitum and Zanthoxylum schinifolium showed the highest level in heat release and smoke release, respectively. Therefore, we have concluded that Lespedeza maximowiczii has the highest ignitibility, Zanthoxylum piperitum the most intensive fire spread and fire intensity, and Zanthoxylum schinifolium and Lespedeza maximowiczii most difficult to escape from a forest fire.