Combustion characteristics of gaseous inverse O₂/H₂ coaxial jet flames in a single-element model combustor

Kim, Tae Young,Choi, Sun,Kim, Young Hoo,Ahn, Yeong Jong,Kim, Hee Kyung,Kwon, Oh Chae Elsevier 2018 ENERGY Vol.155 No.-

<P><B>Abstract</B></P> <P>To effectively design hydrogen (H<SUB>2</SUB>)/oxygen (O<SUB>2</SUB>) liquid rocket engines through understanding the combustion characteristics of H<SUB>2</SUB>/O<SUB>2</SUB> bipropellants, fundamental studies for the bipropellants in different phases are needed. This study is focused on the combustion characteristics of inverse gaseous O<SUB>2</SUB>/H<SUB>2</SUB> coaxial jet flames in a single-element model combustor as a preliminary step for succeeding studies of injection at different phases in the combustor, visualizing flame structure by direct imaging, OH<SUP>∗</SUP> chemiluminescence and OH planar laser-induced fluorescence. With increasing Reynolds number (Re), the frequency of occurrence of the local flame extinction increases and the length of the disconnected OH reaction zone is extended. The OH layer thickness increases downstream, while it is almost constant where the local flame extinction occurs and decreases with increasing Re due to the enhanced strain and scalar-dissipation rates. The excessive flame wrinkledness increases the local flame strain rate and results in the local flame extinction, exhibiting the tendency of increasing and then decreasing flame surface density with increasing Re. The probability density function of OH intensity quantifies the fluctuation intensity of OH radicals and the possibility of the local flame extinction. A useful database is provided for modeling the combustion of H<SUB>2</SUB>/O<SUB>2</SUB> bipropellants under different phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A useful database for modeling the H<SUB>2</SUB>/O<SUB>2</SUB> bipropellant combustion is provided. </LI> <LI> Local flame extinction frequently occurs at high Reynolds number (<I>Re</I>). </LI> <LI> OH probability density function indicates the possibility of local extinction. </LI> <LI> Flame surface density increases and then decreases with increasing <I>Re</I>. </LI> <LI> Strong burning of O<SUB>2</SUB>/H<SUB>2</SUB> causes laminar-like combustion near the injector lip. </LI> </UL> </P>

Properties of inverse nonpremixed pure O₂/CH₄ coflow flames in a model combustor

Choi, Sun,Kim, Tae Young,Kim, Hee Kyung,Koo, Jaye,Kim, Jeong Soo,Kwon, Oh Chae Elsevier 2015 ENERGY Vol.93 No.1

<P><B>Abstract</B></P> <P>In order to evaluate the potential of oxy-combustion of inverse nonpremixed coflow flames using a clean fuel to improve the combustion and emission characteristics compared with the normal coflow flames using air, the fundamental properties of inverse nonpremixed pure oxygen (O<SUB>2</SUB>)/methane (CH<SUB>4</SUB>) coflow flames in a model combustor are experimentally investigated. The combustion stability (extinction) limits, structure and nitrogen oxide (NO<SUB>x</SUB>) emissions of the inverse coflow flames in the quartz-windowed combustion chamber with a single shear coaxial injector and a fully opened exhaust nozzle are measured using OH<SUP>∗</SUP> chemiluminescence, a schlieren imaging system and a gas analyzer. Results show four distinct stability regimes and limits: the attached flame regime, the near-blowout flame regime, blowout limits and blowoff limits. The direct flame and OH<SUP>∗</SUP> chemiluminescence images confirm the cooling effects of chamber walls that cause no steady liftoff flame and only the near-blowout flame. The extinction limits of the inverse CH<SUB>4</SUB>/O<SUB>2</SUB> coflow flames are extended compared with the normal CH<SUB>4</SUB>/air coflow flames and reasonable levels of NO<SUB>x</SUB> emissions are observed, which supports that oxy-combustion of the inverse nonpremixed coflow flames using the clean fuel is acceptable for practical application, providing a useful database for modeling the flames in the confined chamber.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Extended stability limits of inverse nonpremixed O<SUB>2</SUB>/CH<SUB>4</SUB> coflow flames are found. </LI> <LI> Stable, attached flames and oscillating, near-blowout flames are observed. </LI> <LI> Direct flame and OH<SUP>∗</SUP> chemiluminescence images indicate no steady liftoff flame. </LI> <LI> Reasonable levels of NO<SUB>x</SUB> emissions are observed. </LI> <LI> Inverse nonpremixed O<SUB>2</SUB>/CH<SUB>4</SUB> coflow flames are acceptable for practical applications. </LI> </UL> </P>

모델연소실 내 GCH₄/GO₂ 및 GH₂ /GO₂ 동축류 제트화염의 연소특성 기초 연구

최선(Sun Choi),김태영(Tae Young Kim),김희경(Hee Kyung Kim),권오채(Oh Chae Kwon) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12

로켓 엔진의 차세대 액체이원추진제로서 각광을 받고 있는 메탄(CH₄)/산소(O₂) 이원추진제의 기초연소특성 및 연소 안정화의 고유특성 확인을 위해 수소(H2)/산소 이원추진제 연소특성과 비교 연구를 수행하였다. 기초 연소특성 연구를 위한 모델연소실 내에서 기체 메탄(GCH₄)/기체 산소(GO₂) 및 기체수소(GH₂)/GO₂의 동축류 제트화염의 연소안정한계와 직접 사진, OH<SUP>*</SUP> 자발광 이미지를 측정한 결과, GCH₄/GO₂와 GH₂/GO₂ 모두 산소-연료 모멘텀비((O/F)mom)가 감소함에 따라 연소안정한계는 확장되는 경향을 보였으나 GH₂/GO₂ 화염에 비해 GCH₄/GO₂ 화염은 좁은 연소안정한계가 측정되었고, 또한 GCH₄/GO₂ 화염은 이론당량비 조건에서, GH2/GO₂ 화염은 연료과농 조건에서 최대 OH* 강도가 측정됨을 OH<SUP>*</SUP> 자발광 가시화를 통해 확인하였다. Liquid methane (CH₄)/oxygen (O₂) bipropellants have been recently considered as a next-generation propellant due to eco-friendly and non-toxic properties, low cost and high performance. To investigate the unique features of CH₄/O₂ bipropellants, the fundamental combustion characteristics of gaseous CH₄/O₂ and H₂/O₂ coaxial jet flames in a model combustor are investigated through measuring the combustion stability limits and visualizing flames. Results show that the combustion stability limits of GCH₄/GO₂ flames are reduced compared with the GH₂/GO₂ flames. The maximum OH<SUP>*</SUP> intensity of GCH₄/GO₂ flames is observed at near-stoichiometric condition, while the GH₂/GO₂ flames at fuel-rich condition.

모델연소실 내 압력 변화가 메탄/산소 이원추진제의 연소특성에 미치는 영향

최선(Sun Choi),김태영(Tae Young Kim),김희경(Hee Kyung Kim),권오채(Oh Chae Kwon) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5

메탄(CH4)/산소(O2) 액체이원추진제는 친환경성, 무독성, 경제성, 우수한 성능 등의 장점으로 최근 들어 차세대 친환경 이원추진제로서 각광을 받고 있다. 본 연구에서는 연소실 내 압력 변화에 따른 기체 메탄/산소 비예혼합 동축 화염의 연소안정한계를 측정하고, 화염 및 유동의 가시화를 통해 분사조건 및 압력 변화에 따른 화염의 구조와 특성을 파악하였다. 연소안정한계 측정 결과, 연료과농 조건에서 연소실 내 압력이 증가할 경우 연소안정한계가 확장되는 것이 확인되었고 연소(OH*) 강도 역시 크게 증가하는 것을 확인할 수 있었다. Liquid methane (CH4)/oxygen (O2) bipropellant have been recently considered as a next-generation propellant due to eco-friendly and non-toxic properties, low cost and high performance such as specific impulse and regenerative cooling capability. In this study, the combustion characteristics of gaseous CH4/O2 nonpremixed coflow flames in a model combustor with variation of internal pressure are investigated through measuring the combustion stability limits and visualizing flames and flow. Results show that the combustion stability limits are extended and reaction intensity (OH* intensity) is enhanced with increasing internal pressure of the combustion chamber for fuel-rich condition.

Comparison of Melanoma Subtypes among Korean Patients by Morphologic Features and Ultraviolet Exposure

( Hong Sun Jang ),( Jee Hung Kim ),( Kyu Hyun Park ),( Jae Seok Lee ),( Jung Min Bae ),( Byung Ho Oh ),( Sun Young Rha ),( Mi Ryung Roh ),( Kee Yang Chung ) 대한피부과학회 2014 Annals of Dermatology Vol.26 No.4

Background: Genetic alterations have been identified in melanomas according to different levels of sun exposure. Whereas the conventional morphology-based classification provides a clue for tumor growth and prognosis, the new classification by genetic alterations offers a basis for targeted therapy. Objective: The purpose of this study is to demonstrate the biological behavior of melanoma subtypes and compare the two classifications in the Korean population. Methods: A retrospective chart review was performed on patients found to have malignant melanoma in Severance Hospital from 2005 to 2012. Age, sex, location of the tumor, histologic subtype, tumor depth, ulceration, lymph node invasion, visceral organ metastasis, and overall survival were evaluated. Results: Of the 206 cases, the most common type was acral melanoma (n=94, 45.6%), followed by nonchronic sun damage-induced melanoma (n=43, 20.9%), and mucosal melanoma (n=40, 19.4%). Twenty-one patients (10.2%) had the chronic sun-damaged type, whereas eight patients (3.9%) had tumors of unknown primary origin. Lentigo maligna melanoma was newly classified as the chronic sun-damaged type, and acral lentiginous melanoma as the acral type. More than half of the superficial spreading melanomas were newly grouped as nonchronic sun-damaged melanomas, whereas nodular melanoma was rather evenly distributed. Conclusion: The distribution of melanomas was largely similar in both the morphology-based and sun exposure-based classifications, and in both classifications, mucosal melanoma had the worst 5-year survival owing to its tumor thickness and advanced stage at the time of diagnosis. (Ann Dermatol 26(4) 485~490, 2014)

모델연소실 내 산소-메탄 비예혼합 역확산화염의 연소특성 연구

최선(Sun Choi),김태영(Tae Young Kim),김희경(Hee Kyung Kim),권오채(Oh Chae Kwon) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5

지구온난화로 인한 기후변화에 대응하기 위해 다양한 노력이 요구되는 가운데 연소효율을 증가시키고 공해물질의 배출을 저감할 수 있으며 연소 후 이산화탄소 포집이 용이한 산소-메탄 비예혼합 역확산화염의 연소특성에 대한 연구를 수행하였다. 모델연소실 내에서 산소-메탄 비예혼합 역확산화염의 연소안정한계를 측정하고, 화염구조 파악을 위해 OH* 자발광 기법을 통해 반응영역을 확인하였다. In response to the concern over global warming, there has been substantial interest in either developing high-efficiency or low-emission combustion devices. The use of inverse nonpremixed oxygen (O₂)-methane (CH₄) flames as one possible technology for achieving the high-efficiency and low-emission is considered and thus the combustion characteristics of the oxy-fuel inverse flames in a model combustor are experimentally investigated. The combustion stability limits and structure of O₂-CH₄ inverse flames are measured using OH* chemiluminescence.

The role of FGF-2 in smoke-induced emphysema and the therapeutic potential of recombinant FGF-2 in patients with COPD

Kim, You-Sun,Hong, Goohyeon,Kim, Doh Hyung,Kim, Young Min,Kim, Yoon-Keun,Oh, Yeon-Mok,Jee, Young-Koo Nature Publishing Group UK 2018 Experimental and molecular medicine Vol.50 No.11

<▼1><P>Although the positive effects of recombinant fibroblast growth factor-2 (rFGF-2) in chronic obstructive pulmonary disease (COPD) have been implicated in previous studies, knowledge of its role in COPD remains limited. The mechanism of FGF2 in a COPD mouse model and the therapeutic potential of rFGF-2 were investigated in COPD. The mechanism and protective effects of rFGF-2 were evaluated in cigarette smoke-exposed or elastase-induced COPD animal models. Inflammation was assessed in alveolar cells and lung tissues from mice. FGF-2 was decreased in the lungs of cigarette smoke-exposed mice. Intranasal use of rFGF-2 significantly reduced macrophage-dominant inflammation and alveolar destruction in the lungs. In the elastase-induced emphysema model, rFGF-2 improved regeneration of the lungs. In humans, plasma FGF-2 was decreased significantly in COPD compared with normal subjects (10 subjects, <I>P</I> <I>=</I> 0.037). The safety and efficacy of inhaled rFGF-2 use was examined in COPD patients, along with changes in respiratory symptoms and pulmonary function. A 2-week treatment with inhaled rFGF-2 in COPD (<I>n</I> = 6) resulted in significantly improved respiratory symptoms compared with baseline levels (<I>P</I> <I><</I> 0.05); however, the results were not significant compared with the placebo. The pulmonary function test results of COPD improved numerically compared with those in the placebo, but the difference was not statistically significant. No serious adverse events occurred during treatment with inhaled rFGF-2. The loss of FGF-2 production is an important mechanism in the development of COPD. Inhaling rFGF-2 may be a new therapeutic option for patients with COPD because rFGF-2 decreases inflammation in lungs exposed to cigarette smoke.</P></▼1><▼2><P><B>Lung disease: Inhaling a protein might help</B></P><P>Studies on the role of the protein ‘fibroblast growth factor-2’ (FGF-2) in chronic obstructive pulmonary disease (COPD) suggest that inhaled FGF-2 could help treat the emphysema linked to smoking. Researchers in South Korea led by Young-Koo Jee at Dankook University, Cheonan, and Yeon-Mok Oh at the University of Ulsan, Seoul, studied the role of the reduced FGF-2 levels found in mice with lung inflammation caused by exposure to cigarette smoke. They also uncovered details of a protective effect of inhaled FGF-2, identifying specific cellular and lung structure changes attributed to the administered FGF-2. Reduced FGF-2 levels were also found in patients with COPD. Initial trials revealed some improvement in patients treated with FGF-2, but not at a statistically significant level. Nevertheless, the authors suggest their results justify further investigation of the protein’s therapeutic potential.</P></▼2>

초·중·고등학교 학생, 학부모, 일반교사의 보건교육 요구

윤순녕,김영임,최정명,조희순,김영희,박영남,오경순,이분옥,조선녀,조소영,한선희,하영미 韓國學校保健學會 2004 韓國學校保健學會誌 Vol.17 No.2

Purpose : The purpose of this study was to identify needs of health education of the students, parents, general teachers, and health teacher of the elementary, middle, and high schools. Method : 279 schools of elementary, middle, and high school were sampled nonproportionally during the period from June 28 to July 26, 2004 . The data were collected by the questionnaire from 1,888 students, 1,876 parents, 1,695 general teachers, 279 health teachers. A frequency, % and χ2-test were used to analysis by SAS program. Result : 1. It showed that 98.1% of elementary school students, 92.3% of middle school students, 89.6% of high school students answered that they need health education. The most of students, parents, and general teachers had high interests in health education. 2. In the case of students, main causes of needs of health education was 'to prevent diseases or accidents''. But parents answered that it was 'to build up a healthier behavior'. General teachers answered that it was 'more effective systematic and continuous health education'. 3. Over 80% of students, parents, and general teachers about the question of who qualified person is to teach health education as a regular class responded that health teacher is available. Especially 93% of elementary school students answered like that. 4. The most of students, parents, and general teachers answered that health education in the classroom is favorable 1 to 2 hours per week. Conclusion : As results of the study , the majority of students, parents, general teachers agreed needs of health education. Therefore, on the basis of this study, systematic and continuous health education is necessary. Additionally the establishment of independent health subject is required certainly.

노년기 주관적 연령과 건강노화와의 관계: 연령집단별 분석

최은영 ( Choi Eun Young ),조성은 ( Cho Sung Eun ),오영삼 ( Oh Young Sam ),장희수 ( Chang Hee Su ),김영선 ( Kim Young Sun ) 한국보건사회연구원 2017 保健社會硏究 Vol.37 No.1

본 연구의 목적은 노년기 주관적 연령(스스로를 노인 혹은 비(非)노인으로 인지하는지 여부)과 건강노화와의 관계를 연령집단에 따라 검증하는 것이다. 이를 위해 2014년 노인실태조사 대상자 중 연소노인(65~74세)과 고령노인(75~84세)을 연구대상으로 선정하였다. 연구의 주목적인 주관적 연령과 건강노화 간의 관련성을 검증하기 위해 연소노인 및 고령노인 집단별로 다중회귀분석(multiple regression analysis)을 실시하였다. 연구결과, 주관적 연령과 건강노화의 관계는 연령집단별로 다른 양상을 보이는 것으로 나타났다. 연소노인에서 주관적 연령이 비(非)노인인 경우, 높은 수준의 인지기능과 적은 만성질환 수, 낮은 수준의 우울, 그리고 높은 수준의 사회활동 참여를 보이는 것으로 밝혀졌다. 반면, 고령노인인 경우 주관적 연령은 인지기능을 제외하고 건강노화의 다른 세 요소와 유의미한 관련이 없었다. 본 연구는 주관적 연령을 건강노화의 새로운 고려요소로 제시하여, 두 요소의 관련성을 통합적인 차원에서 살펴보았다는 의의가 있다. 또한 노인을 연령대에 따라 구별된 집단으로 살펴봄으로써, 주관적 연령과 건강노화의 연관성이 연령집단마다 상이한 양상을 보임을 밝혔다는 의의를 가진다. The purpose of this study is to examine the relationship between subjective age (whether one subjectively perceives himself as `the elderly` or `not the elderly`) and healthy aging. Using data from the 2014 National Elderly Survey (KIHASA), this study selected a total of 9,653 participants consisting of young-olds (aged 65-74) and old-olds (aged 75-84) For both the young-old and the old-old, multiple regression analyses were conducted to examine the research model. In the young-old population, one`s considering oneself as “non-elderly” was significantly associated with higher cognitive functioning, fewer chronic diseases, lower depressive symptoms, and higher level of social engagement. On the other hand, in the old-old population, one`s considering oneself as “non-elderly” was associated only with higher cognitive functioning, and not with the other domains of healthy aging. The findings suggest that subjective age can be considered as an important predictors of older adults` healthy aging. These findings indicate that the association between subjective age and healthy aging has a different pattern depending on the age group.

물질남용 치료프로그램 후 재범여부에 대한 예비적 추적조사 연구

김현수,조선미,오은영,임기영,정영기,윤웅장,이영미 大韓神經精神醫學會 1999 신경정신의학 Vol.38 No.6

연구목적: 본 연구는 물질사범에게 시행되는 수강명령 프로그램의 효과를 재범률을 중심으로 살펴보고자 한 것이다. 방 법: 이 연구의 대상집단은 보호관찰소에서 의뢰받은 물질남용자집단이다. 이들은 법원으로부터 보호관찰, 수강명령, 치료명령, 사회봉사 등을 부과받았다. 총 104명의 대상자집단을 치료프로그램을 이수한 수강군과 비수강군으로 나누었으며 이들에 대한 재범률을 조사하였다. 결 과: 프로그램을 이수한 수강군이 비수강군에 비해 재범률이 낮았다(p<.05). 또한 단기 수강군과 장기수강군의 재범률의 차이를 조사하였는데 대상자 집단의 수가 적기 때문에 장기 수강군의 효과가 통계적으로 입증되지는 않았다. 결 론: 우리는 물질남용자에 대한 정책이 보다 교육적으로 변화할 것을 본 논문을 통하여 제시하려 하였으며 정부 및 법무부는 물질남용자에게 교육과 치료를 제공해주어야만 한다. Objectives: Using recidivism rate, we investigated the outcome after our substance abuse treatment program had been implemented. Methods: Our target population was substance abuse criminals referred by probational office. They either received the parole and probation order, treatment order or social service order from the court. We divided 104 substance abuse criminals into treatment group and non-treatment group. We examined their recidivism rate. Results: We reached a conclusion that treatment group had lower recidivism rate than non-treatment group(p<.0.5). We examined the effectiveness of short-term and long-term programs. However, no effectivess of long-term program was found because the sabject number was too small. Conclusion: We suggest that the strategies for substance abuse should be changed to more educative ones. The Government and Ministry of Justice must provide education and treatment to the substance abuse criminals.