와류형 고압인젝터의 초기분무의 분열 과도현상

최동석,김덕줄,고장권,Choi, Dong-Seok,Kim, Duck-Jool,Ko, Chang-Kwon 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.8

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

UV광 측정용 아조벤젠 코팅된 FBG의 열적 효과 제거 및 파장 의존성에 대한 연구

최동석,김현경,안태정,Choi, Dong-Seok,Kim, Hyun-Kyoung,Ahn, Tae-Jung 한국광학회 2011 한국광학회지 Vol.22 No.2

본 논문에서는 ultraviolet (UV) 광의 세기를 원격으로 측정하기 위한 아조벤젠 (azobenzene) 코팅된 fiber Bragg grating (FBG)를 구현하였다. 아조벤젠 폴리머는 UV 광에 의해서 탄성이 변화하여 FBG의 코어 격자의 주기 변화를 유도하여 중심파장을 이동시킨다. 중심파장의 이동은 UV 광과 UV 이외의 파장대역의 빛에 의해서 복합적으로 발생하는데 중심파장의 이동량은 약 0.18 nm 이다. 측정의 정확성을 향상시키기 위해서 광원의 복사열에 의한 중심파장의 이동을 열차단 필터(thermal filter)를 사용하여 제거한 결과 중심파장의 이동량은 약 0.06 nm로 다소 감소하였지만 분석 결과 열에 의한 이동량이 충분히 제거된 것을 확인하였다. 또한 서로 다른 방법인 열경화법과 UV 경화법으로 각각 제작된 아조벤젠 폴리머를 이용하여 아조벤젠 코팅 FBG를 제작하였고, 각 제조법에 따른 UV센서로서의 적합성을 확인하였다. 몇 개의 밴드패스 필터(band pass filter)를 사용하여 파장에 대한 민감도를 측정한 결과, 단위 UV 세기당 중심파장의 이동량은 370nm 파장 밴드에서 가장 큰 값인 0.029로, 단파장 영역에서 반응성이 우수하다는 사실을 확인 하였다. 아조벤젠 폴리머의 흡수 스펙트럼과 아조벤젠 코팅 FBG의 파장 의존도가 서로 잘 일치하는 것을 확인하였다. In the paper, we have demonstrated an azobenzene-coated fiber Bragg grating (FBG) for monitoring ultraviolet light (UV) intensity in remote measurement. The elasticity of the coated azobenzene polymer is changed by the UV light, which induces a center wavelength change corresponding to the change of the FBG's grating period. The wavelength shift resulting from both UV light and other light with the wavelength out of the UV range was about 0.18 nm. In order to improve the accuracy of the measurement, the center wavelength shift caused by radiant heat of the light source was sufficiently removed by using a thermal filter. The amount of the center wavelength shift was consequently reduced to 0.06 nm, compared to the result without the thermal filter. Also, the FBGs coated by using azobenzene polymer were produced by two different methods; thermal casting and UV curing. Considering temperature dependence, UV curing is more suitable than thermal casting in UV sensor application of the azobenzene-coated FBG. In addition, we have confirmed the wavelength dependence of the optical sensor by means of four different band pass filters. Thus, we found out that the center wavelength shift per unit intensity is 0.029 [arb. unit] as a maximum value at 370 nm wavelength region and that the absorption spectrum of the azobenzene polymer was very consistent with the wavelength dependence of the azobenzene-coated FBG.

와류형 고압 분무의 속도 및 입경분포에 관한 연구

최동석,류경훈,차건종,김덕줄,Choi, Dong-Seok,Ryu, Kyung-Hoon,Cha, Keun-Jong,Kim, Duck-Jool 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.10

High-pressure swirl injectors have usually been employed in Gasoline direct injection engines due to their spray characteristics and the feasibility of their control. Thus the microscopic characteristics of high-pressure swirl spray were investigated by PDA. The correlation between axial and radial velocities and the correlation between droplet size and axial velocity were examined with different axial and radial positions. Two dimensional droplet velocity and its number distribution with size-classified droplets were illustrated. The mean droplet velocity and its SMD were also analyzed at the center of spray, the position having maximum mean axial velocity, and the spray periphery using time dividing method. Finally, the structure of high-pressure swirl spray was presented with the size distribution and velocity profile of droplets.

자동차의 시스템출력 시험방법 개발

최동석(Dongseok Choi),이정기(Jungki Lee),이광범(Kwangbum Lee),권해붕(Heaboung Kwon),용기중(Geejoong Yong) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5

The concept of system power for motor vehicles becomes necessary because multi power sources and drivetrain are adapted in motor vehicles for the energy savings and the precise emission controls. System power is defined as the power is measured on the powertrain test bed. It is possible to measure the wheel torque precisely using the powertrain test bed due to the direct connection between absorber and the end of drivetrain without tire. Two different test methods were developed for system power measurement. One is the acceleration at full load under road load (i.e., Method Ⅰ); the other is the acceleration at full load under constant vehicle speed (i.e., Method Ⅱ). Test vehicles were ICEV, HEV, FCEV, and EV. The drivetrains for the vehicles were AT, CVT, and reduction gear respectively. It was found that ICEV had the lowest maximum system power by the method I due to the efficiency of the drivetrain. The other vehicles were similar results of the maximum system power for two different test methods. Therefore, it could be adopted these two methods for the measurement of system power in motor vehicles.

중생(衆生)의 번뇌(煩惱)와 근본장애(根本障碍)에 대한 일고찰 -『능가경(楞伽經)』을 중심으로-

최동석 ( Dong Seok Choi ) 대구가톨릭대학교 인문과학연구소 2013 인문과학연구 Vol.0 No.19

What is unavoidable in the lives of Sattva is klesa(evil passions). Klesa brings about suffering, which is linked to death. The Buddhists claim that deaths are not the end, and what you did in the past becomes karma and leads to cycles of life, Then why does klesa occur? In addition, after klesa take place, what obscurations are people confronted? The questions would be discussed in this paper. The foundational Sutra selected for the research is four fascicles of Lankaυatara Sutra. As it is in line with the beginning of the Zen Buddhism in China, the book four fascicles of Lankauatara Sutra holds more important position than other translated sutra in the early history of Chinese Zen buddhism. Klesa is the beginning of fundamental problems that prevent people from seeing as it is. Klesa is caused by ignorance and desire, which also invite karma. With Ciyate(accumulated) karrna in our Citta(mind), the activity consciousness from what happened in the past affects us in the present, keeping our consciousness from seeing what is happening before our very eyes correctly. As a result, we distinguish and judge based on parikalpita(imagination) things like imagination and dreams formed by paratantra(reality). That is why we insist only ‘I’ am the right. This paper looks into the causes of klesa, the cycle and penomenon of life and death of citta(Vijnana), and the consequent fundamental obscurations of Sattva, that is, parikalpita and paratantra. When we do not know of the interconnected process, pain ends only as pain, But once we know, we realize that mind is origin of the triple world. That is when yogin begins.

충북 민주지산 물들메나무 분포 및 군락구조 특성

최동석 ( Dong-suk Choi ),안지영 ( Ji-young An ),오충현 ( Choong-hyeon Oh ) 한국환경생태학회 2021 한국환경생태학회지 Vol.35 No.6

본 연구는 충청북도 민주지산의 물들메나무 분포 및 식물군락구조 특성을 밝히고자 시행되었다. 민주지산 내 8개의 조사구(단위면적 400㎡)를 설치하여 물들메나무 우점군락을 조사하였다. 상대우점치는 8개 군락 모두 물들메나무(35.19%; 26.07~42.74%)가 우점하고 있어 지속적으로 세력을 유지할 것으로 판단된다. 흉고직경급별 분석 결과 물들메나무는 2~43㎝까지 비교적 다양한 직경급으로 생육하고 있으며, 개체수가 많아 교란이나 급격한 환경의 변화가 발생하지 않는다면 지속적으로 세력을 유지할 것으로 판단된다. 종다양도(H’)는 0.8498~1.0261, 균재도(J’)는 0.8160~0.9256, 우점도(D)는 0.0789~0.1840, 최대종다양도(H’max)는 1.0414~1.2041로 분석되었다. 물들메나무의 연륜 및 생장량 분석 결과 평균 29.1년(22~58년)의 수령을 보였으며, 연평균 생장량은 군락 G가 5.84㎜로 가장 높았으며, 군락 B가 2.80㎜로 가장 낮았다. 유사도 분석 결과 군락 B와 E, 군락 C와 F, H 간의 유사도지수가 69.0%로 가장 높았으며, 군락 E와 F 간의 유사도지수가 29.6%로 가장 낮았다. 연구대상인 물들메나무군락지는 분포지가 매우 협소하고, 개체군 크기가 작아 산림유전자원보호지역으로 보전하는 것이 필요하다. The objective of this study was to examine vegetation community structure and distribution of Fraxinus chiisanensis in Mt.Minjuji of Chungcheongbuk-do by setting up and surveying 8 plots (400 m² each). Mean Importance Value (MIV) of Fraxinus chiisanensis in 8 plots was 35.19% in average (ranging from 26.07~42.74%). Since it is the dominant species in all plots, it is expected to maintain the present vegetation structure. The analysis of the DBH (diameter at breast height) showed that the diameter of Fraxinus chiisanensis in Mt.Minjuji ranges from 2 to 43㎝. The majority of Fraxinus chiisanensis is expected to maintain current state unless disturbance or rapid environmental change occurs. The Species Diversity (H’) was 0.8498~1.0261, Evenness (J’) was 0.8160~0.9256, Dominance Index (D) was 0.0789~0.1840, Maximum Diversity (H’max) was 1.0414~1.2041. The analysis of annual ring and radial growth showed that the average age of Fraxinus chiisanensis in Mt.Minjuji was 29.1years(ranging from 22~58years). The average annual radial growth of Fraxinus chiisanensis was the highest in community G with 5.84㎜ and the lowest in community B with 2.80㎜. The similarity index analysis revealed that the similarity index between community B and E, C and F, H was the highest with 69.0%, and the similarity index between community E and F was the lowest with 29.6%. Both the area of Fraxinus chiisanensis community of Mt.Minjuji and its population size are very small. Therefore, this area needs to be designated as Forest Genetic Resource Reserve.

대형 디젤엔진 시험모드에 따른 배출가스 발생특성

최동석(Dong-Seok Choi),엄성복(Sungbok Eom),김남용(Namyong Kim),박용성(Yongsung Park),이종현(Jonghyun Lee),용부중(Boojoong Yong) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1

The emission characteristics were compared by two different emission test cycles for heavy-duty diesel engines. One is ECE R-49 test cycle and the other is ESC. In order to investigate the performance of both test cycles, a heavy-duty diesel engine for a city bus was used with and without after-treatment device. Smoke opacity was also measured to observe the instantaneous smoke value for both test cycles. It was found that more gas emissions produced in ECE R-49 test cycle while more PM created in ESC test cycle without DPF. Smoke opacity was proportional to the engine power and had higher values in the ESC test cycle.

직분식 가솔린 가시화 엔진에서 분사시기에 따른 연소특성

최동석(Dong-Seok Choi),이용석(Yongseok Lee),최재준(Jaejoon Choi),배충식(Choongsik Bae) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1

The mixture distribution and combustion characteristics in a DISI optical engine with a single cylinder were investigated under homogeneous and stratified charge modes. The process of mixture formation was observed using tracer Laser Induced Fluorescence (LIF) technique. 3-pentanone as tracer was employed. The 266nm harmonic beam of the Nd:YAG laser was used to excite the tracer in the motored engine. A part of piston cavity was made of quartz to visualize the processes of mixture formation. Two different injection timings, which are 270°BTDC and l15°BTDC, were set to simulate both charge modes. The effect of injection timings on the stratified mixture distribution and combustion was investigated Fuel distnbution surrounding the spark plug was particularly observed from LIF images. From these experimental information under non-combustion and combustion atmosphere, it will be predicted the region where pollutant emissions could be formed.

[연료 및 윤활유부문] LPG 액상분무의 분열 및 혼합특성

최동석(Dong-Seok Choi),최재준(Jaejoon Choi),배충식(Choongsik Bae) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_1

The interaction between airflow and liquid phase LPG (Liquid Petroleum Gas) sprays was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside intake port of LPG engines. The spray development in flowing fields \\ith the mean velocities of 5.4 and 42.4m/s was identified by spray visualization techniques such as Mie scattering and shadowgrnph. The microscopic visualization using a telescopic lens system was performed to investigate the shape and size of liquid droplets in the spray. The spray structure was identified into three phases: initial stage with a spiral vortex., end stage of injection recirculated with large-scale eddies, and stage after the end of injection governed by airflow. SMD at spray center (10mm downstream) was about 27?? and about 13% bigger than that at spray edge (12mm below nozzle hole). As air velocity increased, SMD at both positions became about 10% smaller

직분식 가솔린 가시화 엔진의 성층연소 특성

최동석(Dong-Seok Choi),이용석(Yongseok Lee),최재준(Jaejoon Choi),배충식(Choongsik Bae) 한국자동차공학회 2002 한국자동차공학회 Symposium Vol.2002 No.11

This study investigated combustion characteristics paying particular attention to a mass flow rate pattern under<br/> stratification charge mode. The mass flow rate was changed using two injector drivers with different operating<br/> characteristics for an injector. These injection systems were employed in an optical single-cylinder engine. Three<br/> different injection timings under late injection modes were set to simulate the stratification charge combustion. To<br/> obtain the mass flow rate, the experiments of fuel metering and injection rate measurement were performed with a<br/> fixed injection quantity. In-cylinder pressure was measured to analyze combustion characteristics. Initial flame size and<br/> its developments were also visualized. In addition, the mixture distribution prior to ignition was obtained using PLIF<br/> technique. As the mass flow rate has a higher value, more stable and faster combustion was achieved. The mixture<br/> distribution showed more uniform and higher concentration in the bowl near the spark plug as the mass flow rate<br/> increases.