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>

남자 고등부 태권도 경기 내용 분석 : 발기술을 중심으로 Focused on Feet Technigues

권오륜,노영태,황영성 釜山大學校 附設 體育科學硏究所 1997 體育科學硏究所 論文集 Vol.13 No.-

This worker has wanted to make out various feet techinques and basic data for improving competitions by analyzing feet techniques frequencies, and effective piont scoring scale in High School Boys' national competitions. Through the study of practical examples, this worker has made these following conclusion: 1. The four different feet techniques were used at The National Olympics, The League of Middle High School Students, and The Pusan Preliminary Matches for the National Olympics in the following various frequencies ; Dolyechagi 222 times(52%), Nalaechagi 63 times(15%), Butchechagi 48 times(11%), and Dutchagi 49 times(11%). 2. An effective point scoring scale could be arranged like this : Dolychagi 45 points(55%), Nalaechagi 12 points(15%), Dutchagi 9 poins(11%), Butchechagi 6 paints(7.3%). 3. The various feet techniques and effective point scoring scale in Tae Kwon Do competitions. These conditions could be especially important for the favored winners. 4. Tae Kwon Do players should practice not only basic techniques but also various feet techniques in order to perform active and aggressive matches.

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.

가스터빈 열병합용 폐열회수 보일러의 열설계 및 해석

오시덕,권용호,김태국 중앙대학교 기술과학연구소 1994 기술과학연구소 논문집 Vol.24 No.-

In this study a computer program has been developed to analyze the thermal and hydraulic performance of waste heat recovery boilers. Using the program developed in this study, the thermal and hydraulic performance data of a 3T/hr boiler are obtained for 100%, 75%, 50% and 25% loads. The results include the expected steam capacity, the local gas/water temperatures, and gas side pressure drop etc. For 100% load, comparison of the current results with those obtained from existing boiler code show fairly good agreements.

菜種油의 水素添加反應에 關한 硏究 (第一報) : 요오드價, 굴절율, 융점의 變化에 따른 Kinetics The Kinetic Studies by the Changes of Iodine Value, Refractive Index and Melting Point

權泰鳳,吳成基 慶熙大學校 1983 論文集 Vol.12 No.-

Edible rapeseed oil containing about 30% erucic acid was hydrogenated using nickel catalyst under 1 atm. and other various reaction conditions. Physicochemical change of the reaction products was examined by measuring iodine value, refractive index and melting point. Also, the kinetics was studied by measuring iodine value. The results obtained are as followed: It was found that the hydrogenation of rapeseed oil at 170℃ and 0.1% catalyst level was followed the first-order kinetic, and the rate constant was calculated to be 3.9×10^-3 min^-1·Iodine value was decreased with an increase of reaction temperature, time and catalyst concentration. Refractive index and melting point were increased with a decrease of iodine value. The correlation factor between refractive index and iodine value was RI=0.00015 IV+1.4512.

HIPP: 고관여제품의 구매의사결정 지원시스템의 설계 : DEA와 AHP의 통합접근

오태민,김민용,권오병 경희대학교 국제경영연구소 2004 국제경영연구 Vol.10 No.1

各種 喀痰消化劑가 抗酸菌死滅에 미치는 影響

權智順,權五溶,崔大卿,白太鉉 충남대학교 의과대학 지역사회의학연구소 1985 충남의대잡지 Vol.12 No.1

For the isolation of mycobacteria in sputum specimens, it is essential to use the most gentle procedure of digestion system for the survival of organisms. The present studies were undertaken to evaluate and compare the effect of various sputum digestants on the death of Mycobacterium fortuitum and Mycobacterium tuberculosis. The results were summarized as follows: 1. Death rates of M. tuberculosis in a solution of 2% NaOH, 3% NaOH and 4% NaOH digestants after 30 minutes of contact time were 97.1%, 97.6% and 97.9%, respectively. In the digestants of 2% NaOH, 3% NaOH and 4% NaOH solution after 1 hour of contact time, survival rates were less than 2%. 2. Death rates of M. tuberculosis in Zephiran-N-acetyl-L-cysteine digestant after 30 and 60 minutes of contact time were 28.5% and 39.5%, while those of M. fortuitum after the contact time were 74.1% and 81.2%, respectively. 3. Death rates of M. tuberculosis in Zephiran-trisodium phosphate digestant after 30 and 60 minutes of contact time were 36.1% and 40.3%, and those of M. fortuitum after the contact time were 71.6% and 74.2%, respectively. 4. Death rates of M. tuberculosis and M. fortuitum in N-acetyl-L-cysteine-NaOH (2%) digestant were similar to the digestant of 2% NaOH solution.

汚染된 河川底泥로부터 營養鹽 溶出에 關한 硏究

權五億,徐承敎,姜善泰 대구산업정보대학 1992 논문집 Vol.6 No.-

Past dicharges of settleable and colloidal organic solids into natural waterways have resulted in appreciable accumulations of sediment in the botton of many lakes, estuaries and river stretches over the years. Under such conditions, bottom sediments, when present, may be come one of the most important factots influencing the quality of natural water. Thus, this study was performed to investigate the nutrients release through chamber experimentation at Gangchang bridge which one of polluted places in Kumho River. The coefficients of sediment oxygen demand for aerobic and anaerobic conditions were 0.864, 5.04 day^(-1), respectively. Also, the release rate of NH₃-N and PO₄-P for aerobic conditions were 0.242g/m²·day, 0.029g/m²·day, and the released rate of NH₃-N and PO₄-P for anaerobic condition were 0.665g/m²·day, 0.186g/m²·day, respectively.

HIPP: 고관여제품의 구매의사결정 지원시스템의 설계 : DEA와 AHP의 통합접근

오태민,김민용,권오병 경희대학교 기업경영연구소 2004 기업경영연구 Vol.10 No.1

본 연구는 다속성의 고관여제품의 구매에 있어서 개인화된 의사결정 지원시스템을 제시하였다. HIPP 시스템은 단순한 가격비교 에이전트가 아니라 소비자의 선호에 적합한 제품을 찾아내는 쇼핑 에이젼트로서 소비자의 구매의사결정을 효과적으로 지원하게 된다. 이러한 방법이 실제 전자상거래에 활용될 경우에 공급자는 소비자에게 새로운 형태의 효과적인 에이전트를 제공함으로색 고객 흡입효과를 높일 수 있다. 그리고 소비자는 구매 시 많은 정보가 요구되는 고관여 제품에 있어서 개개인의 선호에 맞는 구매정보를 제공받을 수 있다. 본 연구는 '객관적으로 효을적인 제품군을 발견하기 위해 DEA 기법을 적용하였고, 여기에 소비자 개인의 상대적인 선호도를 반영하기 위한 AHP 방법을 결합하여 새로운 유형의 개인화된 의사결정지원 시스템인 HIPP 시스템을 설계하였고, 노트북 PC 구매의 시나리오를 통하여 시스템의 프로세스를 제안하였다. Currently, there has been an increase in purchasing high-involvement products such as automobile, personal computers, and A/O components at the Internet shopping malls.' And for the purpose of supporting consumers in purchasing high-involvement products, many comparative shopping agents have been developed. However, most shopping agents simply compare the prices of products and hence lack of reflecting consumers' preferences. Ws a result, too much variety of alternative products and product complexity is hindering the efficient purchasing decision. This study aims at developing customized decision support system in purchasing multi-attribute high-involvement products to overcome such difficulties. In designing HIPP decision support system, we integrate DEW and WHO methods. By using DEW, consumers can find efficient product groups consisting of the "best performance" products, which reduces the information overload. Next, WHO is applied to the efficient products groups. Since WHO can reflect consumer's relative preferences for products attributes, more personalized purchase support can be possible. We demonstrate the HIPP decision support system under the scenario in which consumer wants to purchase a notebook PC.