• Title/Summary/Keyword: 액체 수소

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Behavior of the Ultrasonically-atomized Liquid-fuel Flame Injected through a Slit-jet Nozzle (Slit-jet 노즐을 통해 분사되는 초음파 무화 액체연료 화염의 거동)

  • Kim, Min Cheol;Kim, Min Sung;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.6
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    • pp.1-10
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    • 2018
  • An experimental study was performed for the behavior of the burner flame which results from burning of the liquid hydrocarbon fuel atomized by an ultrasonic transducer. Configurations of the flame and combustion-field were caught by both high-speed camera and thermo-graphic camera, and those images were analyzed in detail through a image post-processing. As a result, the combustion-field grew and reaction-temperature rose due to the strengthening of combustion reaction with the increasing flow-rate of carrier-gas. In addition, a phenomenon of flame flickering was discussed through the comparative analysis of the variational behavior between the visible flame and IR (Infrared) flame-field. Also, the flickering frequency of the flame was confirmed through FFT (Fast Fourier Transform) analysis employing the flame area.

Application of Artificial Neural Network to Flamelet Library for Gaseous Hydrogen/Liquid Oxygen Combustion at Supercritical Pressure (초임계 압력조건에서 기체수소-액체산소 연소해석의 층류화염편 라이브러리에 대한 인공신경망 학습 적용)

  • Jeon, Tae Jun;Park, Tae Seon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.6
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    • pp.1-11
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    • 2021
  • To develop an efficient procedure related to the flamelet library, the machine learning process based on artificial neural network(ANN) is applied for the gaseous hydrogen/liquid oxygen combustor under a supercritical pressure condition. For hidden layers, 25 combinations based on Rectified Linear Unit(ReLU) and hyperbolic tangent are adopted to find an optimum architecture in terms of the computational efficiency and the training performance. For activation functions, the hyperbolic tangent is proper to get the high learning performance for accurate properties. A transformation learning data is proposed to improve the training performance. When the optimal node is arranged for the 4 hidden layers, it is found to be the most efficient in terms of training performance and computational cost. Compared to the interpolation procedure, the ANN procedure reduces computational time and system memory by 37% and 99.98%, respectively.

동축형 분사기 분무특성 및 연소의 이론적 모델

  • 원영덕;윤웅섭;김영수;윤경택
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2000.04a
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    • pp.4-4
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    • 2000
  • 일반적인 액체추진제 로켓엔진의 연소는 분사제트의 미립화, 액적의 증발, 기상 추진제의 혼합, 화학반응 등, 일련의 물리적 과정들로 이루어지고, 여기서 특성속도 효율은 크게 분사특성 및 연소의 두 단계에서 결정되게 된다. 액체추진제 로켓엔진에 사용되는 여러 분무형태 중, 동축형 분사기에서는 액상과 기상 제트의 운동량 차에 의해 미립화가 이루어지며, 분무 액적들의 전개와 더불어 분사기 출구를 포함한 전 영역에서 연소가 발생되므로 매우 복잡한 물리적 특성들을 포함하게 된다. 본 연구에서는 기상 연료-액상 산화제의 동축형 분무연소를 JANNAF의 방법을 사용하여 수식화 하였으며, 이를 바탕으로 분무특성과 연소성능 예측을 위한 프로그램을 작성, 분사조건에 의한 분무특성과 그에 따른 연소성능을 계산하였다. 연속, 운동량, 에너지 및 혼합비 방정식의 지배방정식들을 바탕으로 기상 유동을 수식화 하였으며, 별도로 액적의 소산 및 연소과정을 모사하기 위한 별도의 수식들이 추가되었고, 이 식들을 결합하여 액적의 크기, 분포를 포함하는 액체 제트의 미립화 정도를 공간적으로 계산하였다. 미립화 모델의 검증을 위하여 계산 결과를 Reitz의 실험과 Giridharan의 모델 등과 비교하였으며 잘 일치하는 경향을 나타내었다. 또한 동축형 분사기에서의 분무 특성을 예측하기 위해 액체 산소, 기체 수소를 추진제 조합으로 하는 동축형 분무 연소장에서의 제트 길이, 액적의 크기, 액체 제트의 속도를 계산하였다. 계산 결과 액체 제트의 접촉길이는 분사공의 지름이 증가할수록 웨버수가 증가되므로 짧아지는 것으로 관찰되었으며 액적의 크기도 분사공의 지름이 증가할수록 작아지는 경향을 나타내었다. 액체 제트의 속도는 처음에는 일정하게 유지되다가 운동량을 보존하기 위해 가스로부터 운동량을 받아 점차 가속되어지는 것으로 나타났다.본 규격은 키, 총장, 어깨길이, 등길이, 머리길이, 머리둘레, 진동둘레, 목둘레, 가슴둘레, 허리둘레, 배둘레, 엉덩이둘레, 앞품, 뒤품, drop치를 포함하고 있고, 각 규격에서 호칭간 치수 간격도 함께 제시하고 있다. 본 연구 결과에서 보듯, 현행 8규격의 무진복의 각 호칭간 적정 허용범위를 고려해 합리적인 치수체계를 정립한다면 치수에 대한 적합도가 상당히 증가할 뿐 아니라 생산비용도 상당히 감축할 것으로 생각된다.나타났다. 4) 호감적 서비스능력 차원에서 세 독립변수간에 유의한 3원 상호작용이 존재하는 것으로 나타나( $F_{2,228}$=15.62, P<.001) 20대에 적합한 의복 착용시( $F_{2,228}$=3.98, P<.05)와 60대에 적합한 의복 착용시( $F_{2,228}$=16.55, P<.001) 점포유형과 격식차림간에는 유의한 상호작용이 존재하는 것으로 나타났다. 5) 호감을 구성하는 세 요인들이 구매의도에 미치는 영향을 조사한 결과 호감적 인상차원은 29%(P<.001), 호감적 서비스능력차원은 6%(P<.001)의 구매의도를 설명해 주는 것으로 나타났다. 본 연구결과 노년 소비자에게 호감을 주는 판매원의 외모는 구매의도에 영향을 주어 실버의류산업의 이익증대와 밀접한 연관을 갖는 서비스품질의 중요한 요인으로 밝혀졌다.중요한 요인으로 밝혀졌다.로운 단백질 EPSPS가 다른 여러 식물에 이미 존재하고 있는 단백질로서 우리가 이미 이러한 식품을 섭취할 때 이 단백질도 같이 섭취해오고 있었다는 점, 둘째. 이 단백질이 소화액 분해 실험에서 짧은 시간내에 분해가 되었다는 점, 셋째. 재조합 된 콩과 자연 콩이 성분 분석에서 차이를 나타내지 않았다는 점, 네 번째. 쥐를 통한 다양섭취 실험에서 아무런 이상 반응이 없었

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Tritium Concentrations of Tritiated Water Vapor and Tritiated Hydrogen in the Atmosphere in Taejon (대전지역 대기중 수증기상태 (HTO) 및 가스상태 (HT) 삼중수소의 농도)

  • Kim, C.K.;Han, M.J.;Kim, K.H.
    • Journal of Radiation Protection and Research
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    • v.22 no.2
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    • pp.97-101
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    • 1997
  • During the period of March 1995 to December 1995, tritium concentrations of tritiated water vapor (HTO) and tritiated hydrogen (HT) in the atmosphere in Taejon were measured to evaluate present background levels of tritium in the atmosphere. Air samples were collected continuously for three weeks with a sampling system for tritium in the atmosphere and were analyzed by a liquid scintillation counting system. The range of the atmospheric HTO concentrations was 3.2-36 mBq $m^{-3}$ with a mean value of 16.2 mBq $m^{-3}$. The atmospheric HTO concentrations were the highest in summer and the lowest in winter. This trend was similar to the variation of atmospheric absolute humidity. The specific activities of tritium in atmospheric water vapor in Taejon ranged from 0.62 Bq $L^{-1}$ to 3.82 Bq $L^{-1}$ with a mean value of 2.04 Bq $L^{-1}$. The atmospheric HT concentrations were in the range of 35.7 mBq $m^{-3}$ to 48.9 mBq $m^{-3}$ with a mean value of 41.1 mBq $m^{-3}$.

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Antifungal effect of electrolyzed hydrogen water on Candida albicans biofilm (Candid albicans 바이오필름에 대한 전기분해 수소수의 항진균 효과)

  • Pyo, Kyung-Ryul;Yoo, Yun Seung;Baek, Dong-Heon
    • Journal of Dental Rehabilitation and Applied Science
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    • v.31 no.3
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    • pp.212-220
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    • 2015
  • Purpose: Candida albicans can cause mucosal disease in many vulnerable patients. Also they are associated with denture-related stomatitis. Electrolyzed water is generated by electric current passed via water using various metal electrodes and has antimicrobial activity. The aim of this study was to investigate antifungal activity of electrolyzed water on C. albicans biofilm. Materials and Methods: C. albicans was cultured by sabouraud dextrose broth and F-12 nutrient medium in aerobic and 5% $CO_2$ condition to form blastoconidia (yeast) and hyphae type, respectively. For formation of C. albicans biofilm, C. albicans was cultivated on rough surface 6-well plate by using F-12 nutrient medium in $CO_2$ incubator for 48 hr. After electrolyzing tap water using various metal electrodes, the blastoconidia and hyphal type of C. albicans were treated with electrolyzed water. C. albicans formed blastoconidia and hyphae type when they were cultured by sabouraud dextrose broth and F-12 nutrient medium, respectively. Results: The electrolyzed water using palladium electrode (EWP) exhibited antifungal effect on blastoconidia of C. albicans. Also, the EWP significantly has antifungal activity against C. albicans biofilm and hyphae. In the electrolyzed water using various metal electrodes, only the EWP have antifungal activity. Conclusion: The EWP may use a gargle solution and a soaking solution for prevention of oral candidiasis and denture-related stomatitis due to antifungal activity.

Tritium Distribution in Some Environmental Samples-Rices, Chinese Cabbages and Pine Needles in Korea (국내 환경시료(쌀, 채소, 솔잎) 중 삼중수소의 분포)

  • Kim, Chang-Kyu;Cho, Yong-Woo;Han, Man-Jung;Pak, Chan-Kirl
    • Journal of Radiation Protection and Research
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    • v.17 no.2
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    • pp.25-35
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    • 1992
  • To evaluate tritium level in some environmental samples, tissue-free water tritium (TFWT) and tissue-bound tritium (TBT) were analyzed in rices, chinese cabbages and pine needles collected at 12 locations in Korea. The TFWT was recovered by freeze-drying of the samples and the TBT was obtained in the form of water by combustion of the dried samples. Tritium was measured by liquid scintillation counter. The concentrations of TFWT were in the range of $0.96{\sim}3.96 Bq/1,\; 0.83{\sim}3.40 Bq/1\;and\;1.02{\sim}3.01 Bq/1$ in rices, chinese cabbages and pine needles, respectively. The mean specific activity ratios (TBT/TFWT) were 0.94, 1.71 and 1.39 in rices, chinese cabbages and pine needles, respectiviely. This excess TBT in the samples may be attributed to the fact that the residence time of TBT in the plant is longer than that of TFWT. The specific activity ratio depends on the plant species, the exposed time to tritiated atmosphere, atmospheric moisture, temperature and diffusion factor.

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Design and Operation of a Small-Scale Hydrogen Liquefier (소형 수소액화기 설계 및 운전에 관한 연구)

  • Baik, Jong Hoon;Karng, Sarng Woo;Kang, Hyungmook;Garceau, Nathaniel;Kim, Seo Young;Oh, In-Hwan
    • Journal of Hydrogen and New Energy
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    • v.26 no.2
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    • pp.105-113
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    • 2015
  • In order to accelerate hydrogen society in current big renewable energy trend, it is very important that hydrogen can be transported and stored as a fuel in efficient and economical fashion. In this perspective, liquid hydrogen can be considered as one of the most prospective storage methods that can bring early arrival of the hydrogen society by its high gravimetric energy density. In this study, a small-scale hydrogen liquefier has been designed and developed to demonstrate direct hydrogen liquefaction technology. Gifford-McMahon (GM) cryocooler was employed to cool warm hydrogen gas to normal boiling point of hydrogen at 20K. Various cryogenic insulation technologies such as double walled vacuum vessels and multi-layer insulation were used to minimize heat leak from ambient. A liquid nitrogen assisted precooler, two ortho-para hydrogen catalytic converters, and highly efficient heat pipe were adapted to achieve the target liquefaction rate of 1L/hr. The liquefier has successfully demonstrated more than 1L/hr of hydrogen liquefaction. The system also has demonstrated its versatile usage as a very efficient 150L liquid hydrogen storage tank.

Analysis on Fluid Dynamics in the Cooling Tube for Manufacture of Liquid Hydrogen (액체수소 제조를 위한 냉각튜브 내 유동장 해석)

  • LEE, DAE-WON;NGUYEN, HOANG HAI;NASONOVA, ANNA;OH, IN-HWAN;KIM, KYO-SEON
    • Journal of Hydrogen and New Energy
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    • v.26 no.4
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    • pp.301-307
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    • 2015
  • We present a study of hydrogen liquefaction using the CFD (Computational Fluid Dynamics) program. Liquid hydrogen has been evaluated as the best storage method because of high energy per unit mass than gas hydrogen, but efficient hydrogen liquefaction and storage are needed in order to apply actual industrial. In this study, we use the CFD program that apply navier-stokes equation. A hydrogen is cooled by heat transfer with the while passing gas hydrogen through Cu tube. We change diameter and flow rate and observe a change of the temperature and flow rate of gas hydrogen passing through Cu tube. As a result of, less flow rate and larger diameter are confirmed that liquefaction is more well. Ultimately, When we simulate the hydrogen liquefaction by using CFD program, and find optimum results, it is expected to contribute to the more effective and economical aspects such as time and cost.

Characterization of Hydrogen Uptake Properties for Titanate Nanotubes (티타네이트 나노튜브의 수소저장 특성 평가)

  • Lee, Nam-Hee;Oh, Hyo-Jin;Yoon, Cho-Rong;Guo, Yupeng;Park, Kyeong-Soon;Kim, Sun-Jae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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    • pp.42-42
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    • 2007
  • 티타네이트 나노튜브는 10 nm 이내의 내경과 0.74nm 정도의 크기를 갖는 층상 구조를 이루고 있어 높은 비표면적을 이용한 수소의 물리적 흡착뿐만 아니라 Ti-H 결합에 의한 화학적 흡착이 동시에 가능하다. 따라서 본 연구에서는 전이금속 원소 중 Ni을 첨가한 티타네이트 나노튜브를 합성하고 수소저장특성을 평가하고자 하였다. 티타네이트 나노튜브는 저온균일침전법으로 제조된 침상형의 $TiO_2$ 분말을 출발원료로 염화니켈을 $TiO_2$의 질량 비로 1~5wt% 첨가하고 10 M의 NaOH 수용액에서 일정시간 혼합한 후 $150^{\circ}C$에서 24시간 수열합성하였다. 합성된 분말의 입자형상 및 결정상은 전자현미경과 X-선 회절 시험을 이용하여 분석하였고, 입자의 비표면적은 액체질소흡착법을 이용하여 측정하였다. 전자현미경 관찰결과 이온교환 전후의 입자형상은 큰 변화가 없었던 반면 이온교환 후 입자의 비표면적이 30% 이상 증가함을 확인하였다. 특히 Ni의 도핑량이 증가함에 토라 입자의 비표면적도 함께 증가하였으며, 전자현미경 관찰결과 더욱 미세한 나노튜브가 형성됨을 확인할 수 있었다. P-C-T를 이용하여 측정한 순수한 티타네이트 나노튜브의 수소저장량이 20기압에서 1.2 wt% 정도로 측정된 반면 Ni이 5 wt% 첨가된 티타네이트 나노튜브의 경우 같은 압력에서 1.6 wt%를 나타내었다.

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A Simulation Study on the Hydrogen Liquefaction through Compact GM Refrigerator (소형 GM 냉동기를 이용한 수소 액화에 관한 시뮬레이션 연구)

  • JUNG, HANEUL;HAN, DANBEE;YANG, WONKYUN;BAEK, YOUNGSOON
    • Journal of Hydrogen and New Energy
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    • v.33 no.5
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    • pp.534-540
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    • 2022
  • Liquid hydrogen has the best storage capacity per unit mass and is economical among storage methods for using hydrogen as fuel. As the demand for hydrogen increases, the need to develop a storage and supply system of liquid hydrogen is emphasizing. In order to liquefy hydrogen, it is necessary to pre-cool it to a maximum inversion temperature of -253℃. The Gifford-McMahon (GM) refrigerator is the most reliable and commercialized refrigerator among small-capacity cryogenic refrigerators, which can extract high-efficiency hydrogen through liquefied hydrogen production and boil of gas re-liquefaction. Therefore, in this study, the optimal conditions for liquefying gas hydrogen were sought using the GM cryocooler. The process was simulated by PRO/II under various cooling capacities of the GM refrigerator. In addition, the flow rate of hydrogen was calculated by comparing with specific refrigerator capacity depending on the pressure and flow rate of a refrigerant medium, helium. Simulations were performed to investigate the optimal values of the liquefaction flow rate and compression pressure, which aim for the peak refrigeration effect. Based on this, a liquefaction system can be selected in consideration of the cycle configuration and the performance of the refrigerator.