• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.151.2-151.2
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• 2012

터보펌프 구동에 사용된 가스발생기 생성가스를 연소기로 공급하여 주추력 발생에 사용하는 다단연소 사이클 로켓엔진은 고추력을 요하는 우주 발사체에 널리 사용되고 있다. 다단연소 사이클 로켓엔진에 사용되는 가스발생기를 예연소기라 부르며 케로신과 액체산소를 추진제로 하는 다단연소 사이클 로켓엔진에는 산화제 과잉 예연소기가 사용된다. 예연소기는 터보펌프 구동을 목적으로 하기 때문에 예연소기 생성가스의 횡단면 온도분포는 터빈에 의해 제한되는 온도범위 내에서 균일하여야 하며 넓은 운전영역에서 안정적인 연소가 이루어져야 한다. 산화제 과잉 예연소기는 모든 추진제가 혼합헤드를 통해 분사되는 방식과 추진제를 혼합헤드와 연소실로 나누어 공급하는 방식이 있다. 기술검증을 위해 산화제 일부와 연료를 혼합헤드를 통해 연소실에 공급하여 1차 연소시키고 나머지 산화제를 연소실 냉각채널을 거쳐 연소실 중앙의 분사공을 통해 연소실로 주입하여 기화시키는 형태로 최종적으로 연소압 20MPa, 혼합비 60에서 작동하는 산화제 과잉 예연소기를 설계하여 연소시험을 수행하였다. 혼합헤드에는 별도의 점화용 분사기 없이 전체 연료 분사기를 통해 점화용 연료인 TEA/TEB 혼합물을 분사하여 점화하였다. 추진제를 2단으로 공급할 수 있도록 고안된 가압식 연소시험 설비에서 10회, 누적 60초 이상의 연소시험이 성공적으로 수행되었다. 연소시험결과 넓은 작동영역에서 안정적 연소특성과 생성가스 온도 분포의 균일성을 확인할 수 있었다. 고온 고압의 산화제 과잉 예연소기 기술 확보를 통해 케로신/액체산소 다단연소 사이클 로켓엔진 개발을 위한 기술적 기반을 마련하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.4
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• pp.48-55
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• 2008

In this paper, numerical analysis of the surface gas temperature on turbine blades has been performed to investigate the temperature profiles characteristics of a partial admission supersonic turbine driven by high temperature and pressure gas of pyro-starter with two different types of turbine blade edge shape. In order to examine the surface gas temperature on turbine blades at initial starting, computations tlave been carried out at several turbine rotational speeds in the range of $0{\sim}10,000$ rpm for each type of turbine edge shape. "Sharp" edge and "Round" edge types were taken as the turbine edge shape factor. As turbine rotational speed increased, the average temperature of turbine blades was further decreased. It was also found that the surface temperature of turbine blades with a sharp edge was lower than round-type edge turbine blades.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.536-542
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• 2017

A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assembly for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluated the complex phenomena of nozzle assembly during burning time with co-simulation which include fluid, thermal surface reaction/ablation and structural analysis. The validity of this approach was verified by comparison of analysis results with measured strains.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.857-863
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• 2017

In this paper, the process of electro Ni and electro Cr plating is studied for the purpose of thermal barrier to protect the inner wall combustion chamber. The chamber is under the environment of very high temperature and high pressure when propellants burn in there. As one of the thermal barrier coatings, Zr-based thermal spray coating has been applied to the chamber. However, peeling of coating layer can occur under such a hard condition because of the difference of thermal expansion coefficients between the ceramic and the metallic wall. We study the characteristics of Ni-Cr coating and establish its process. It is found that the thickness of over $100{\mu}m$ of Ni and Cr coating layers with the uniformity of ${\pm}10%$ can be obtained with the used of as-developed plating bath.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.57.1-57.1
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• 2009

나노이산화티타늄은 인체에는 화장품, 의약, 식품분야 등에 쓰이고 외부 환경 재료에는 광촉매로서 유독가스 정화제, 옥내 외 항균, 수소발생 가시광 응답형 촉매 및 멤브레인 필터 등과 전자소재용 유전재료, 발광 재료 등 용도가 다양하다. 나노 산화티타늄 화합물의 제조법은 수열합성법, 기상법 등 여러 방법이 있다. 이들에 대한 리뷰의 목적은 2009년도 정부의 투자 계획 중에서 본제목에 관련되는 핵심 산업 재원 원천기술 개발, 태양광, 풍력 등의 신재생 에너지 개발, 록색 기술 개발을 통한 에너지절약형 LED 개발, 차세대 핵심환경 기술 개발, 핵심나노기반기술개발 등의 개발을 위하여 4,363억 원의 예산을 편성하고 연구자와 기술자들이 참여하여 유익한 실적이 창출되기를 원하고 있으므로 본 발표자들은 이 분야에서 연구하는 연구자와 기술자들에게 이 분야에 관련되는 자료를 참고로 제시하는데 있다. 페로브스카이트형 산화물인 유전재료($BaTiO_3$), 발광재료(CaTiO3:Pr3+적색), 박막형 반응기재료($Ca0.8Sr0.2TiO_3$), 등의 여러 가지 산화물은 류통식 급속 승온 수열 합성법, 겔 졸 법, 수열 합성법 등 여러 방법에 의하여 페로브스카이트형 산화물 입자 직경이 약 20nm~100nm 범위까지 합성된다. 태양광을 조사하여 물을분해 해서 수소를 생산하는 산화티타늄계 가시광 응답형 Vis-$TiO_2$ 박막은 기상법으로 제조하는데 한 예로써 RF 스퍼터링법으로 박막을 제조하여 수소와 산소를 회수하였으며, 황도프산화티타늄, 질소 도프 산화티타늄은 유기물 분해에 의한 공해제거, $NO_x$ 제거 등 환경정화에 사용되고, 고온 고압수법/산화티타늄 복합기술에 의해서는 바이오매스 분해 하고, 일종의 수열법인 개량형 HyCOM 법은 가시광 응답성 산화티타늄을 합성하여 NO가스 제거에 사용한다. 이들 여러 방법에 관한 것을 소개하고저 한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.2
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• pp.165-170
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• 2015

Pipe-rack structures supporting high temperature and pressure are of great importance to ensure the safety of the operation of the plants. If some damage occurred in the pipe-rack structure, the facilities not only bring damage to the commercial property, but also result in economic losses. Specially, since pipe-rack structures are exposed to various environmental conditions, it is essential to evaluate the thermal behavior of the structure caused by environmental conditions for the appropriate design and maintenance of the pipe-rack structure. Thus, based on a selected, typical pipe-rack structure, a thermal-stress coupled analysis was conducted to evaluate the temperature distributions and thermal stresses of the structure. For this, this study accounted for the operating condition of the pipe and the effect of environmental conditions, Yeosu in South Korea and Saudi Arabia in the Middle East. The results of the study showed the need for accounting for a variance in the environmental factors to evaluate the thermal behavior of the pipe-rack structure along with the working condition of pipe.

• Journal of Sensor Science and Technology
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• v.12 no.5
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• pp.199-204
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• 2003

This paper describes on the fabrication and characteristics of a ceramic thin-film pressure sensor based on Ta-N strain-gauges for harsh environment applications. The Ta-N thin-film strain-gauges are sputter-deposited onto a micromachined Si diaphragms with buried cavity for overpressure protectors. The proposed device takes advantages of the good mechanical properties of single-crystalline Si as diaphragms fabricated by SDB and electrochemical etch-stop technology, and in order to extend the operating temperature range, it incorporates relatively the high resistance, stability and gauge factor of Ta-N thin-films. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low non-linearity and excellent temperature stability. The sensitivity is $1.097-1.21\;mV/V{\codt}kgf/cm^2$ in the temperature range of $25-200^{\circ}C$ and the maximum non-linearity is 0.43%FS.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.2
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• pp.101-107
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• 2009

Investigation of resaturation and thermal-hydro-mechanical behavior for the buffer of a repository requires measuring the water content of compacted bentonite. This study investigated the relative humidity of compacted bentonites using a humidity sensor (Vaisala HMT 334) applicable under high temperature and pressure, and then conducted a multi-regression analysis based on the measured results to determine relationships among the water content, relative humidity, and temperature. The relationships for the compacted bentonites with the dry densities of 1,500 $kg/m^3$ and 1,600 $kg/m^3$ were expressed as ${\omega}=0.196RH-0.029T+1.391({r^2=0.96)}$ and ${\omega}=0.199RH-0.029T+2.596({r^2=0.98)}$, respectively. These were then used to interpret the resaturation of bentonite blocks in the KENTEX test.

• Applied Biological Chemistry
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• v.50 no.1
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• pp.6-11
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• 2007

This study was carried out to evaluate the growth characteristics of Propionbacterium freudenreichii KCCM 31227 and production of organic acids in whey broth. Bacterial growth and increase rate of TTA (Total Titratible Acidity) were analysed. Log numbers of Propionibacterium freudenreichii KCCM 31227 was at the highest peak at 7.5${\times}10^7$ cfu/ml in fementation of 72 hr in 12% whey broth treated with low temperature long time method (60$^{\circ}C$, 30min) containing 1% yeast extract. TTA value of 12% whey broth treated with low temperature long time method and containing 1% yeast extract showed the highest peak at 5.2 in fermentation of 72 hr. The increase rate of cells and TTA in whey broth revealed almost the same tendency. Production of propionic and acetic acids showed higher value in the whey broth treated with low temperature long time method.

• Membrane Journal
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• v.7 no.4
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• pp.167-174
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• 1997

The concentration of silica is required to meet a certain level because silica affects fuel and materials integrity by forming a zeolite layer on fuel cladding surfaces. When the established Feed and Bleed method is employed, nuclear waste increase and the corresponding amount of boric acid is constantly consumed. This study concentrates on minimizing the amount of nuclear waste and consumption of boric acid. Using five different membranes, operating conditions such as temperatur, feed water flow rate, boric acid recovery and silica removal rate were examined. A silica-selective removal system was designed based on the above optimization procedures. Three-stage system was designed with two characteristically different membranes so that it could correspond with the different situation easily. Compared to the pevious results of the Feed and Bleed method, the current method showed that the amount of nuclear waste was reduced to 7%, and the consumption of boric acid to 15.7%.