• 한국분말재료학회지
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• 제10권6호
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• pp.390-394
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• 2003

Ultra fine titanium carbide particles were synthesized by novel metallic thermo-reduction process. The vaporized TiC1$_4$+$CCl_4$ gases were reacted with liquid magnesium and the fine titanium carbide particles were then produced by combining the released titanium and carbon atoms. The vacuum treatment was followed to remove the residual phases of MgC1$_2$ and excess Mg. The stoichiometry, microstructure, fixed and carbon contents and lattice parameter were investigated in titanium carbide powders produced in various reaction parameters.

• 대한기계학회논문집B
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• 제32권11호
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• pp.878-883
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• 2008

The spray characteristics of a high pressure 6-hole injector were examined in a single cylinder optical direct injection spark ignition (DISI) engine. The effects of injection timing, in-cylinder charge motion, fuel injection pressure and coolant temperature were investigated using the 2-dimensional Mie scattering technique. It was confirmed that the in-cylinder charge motion played a major role in the fuel spray distribution during the induction stroke while the propagation of fuel spray was restrained during the compression stroke by the increasing pressure and the upward moving piston. In additions, it was confirmed that the liquid fuel droplets existing at the sprays edges were vaporized by the increase of the coolant temperature.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.93-98
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• 2004

An experimental research on supersonic combustion of kerosene in a model scramjet combustor has been conducted. Kerosene was injected normally into a Mach 2 vitiated airstream either at an atomized liquid state or at a gaseous state. The atomization of kerosene was achieved by the “effervescent atomization” method, and the gaseous kerosene was supplied by passing kerosene inside a heated pipe. The results are discussed and are also compared to those in our previous experiment, in which no atomization nor vaporization methods has been conducted to the kerosene.

• 한국전기전자재료학회논문지
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• 제32권6호
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• pp.516-521
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• 2019

The top seeded solution growth (TSSG) method is an alternative technique to grow high-quality SiC crystals that has been actively studied for the last two decades. However, the TSSG method has different issues that need to be resolved when compared to the commercial SiC crystal growing method, i.e., physical vapor transport (PVT). A particular issue of the TSSG method of results from the presence of liquid droplets on the grown crystal that can remain even after crystal growth; this induces residual stress on the crystal surface. Hence, the residual droplet causes several unwanted effects on the crystal such as the initiation of micro-cracks, micro-pipes, and polytype inclusions. Therefore, this study investigated the formation of the residual droplet through multiphysics simulations and lead to the development of a liquid droplet removal method. As a result, we found that although residual liquid droplets significantly apply residual stress on the grown crystal, these could be vaporized by adopting thermal annealing processes after the relevant crystal growing steps.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.721-724
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• 2011

터보펌프에서 발생 가능한 cavitation을 동반하지 않으면서 추진제를 요구하는 압력과 유량으로 연소기에 공급하기 위해서는 추진제 탱크에 저장된 추진제를 가압하는 시스템이 필요하다. 가압시스템은 선가압과 주가압으로 분류할 수 있으며, 본 연구에서는 주가압 시스템에 대해서만 언급한다. 추진제탱크 가압 방식에는 가압가스 생성방법과 공급 방법으로 나눌 수 있으며, 가압가스 생성방법으로는 비활성가스 및 극저온 산화제를 기화시켜 추진제탱크에 공급하는 방법이 있다. 본 연구에서는 가압시스템의 분류와 가압 방식에 따른 장단점을 비교하였으며, 특히 발사체에서 사용하고 있는 가압방식 중에서 임펄스 제어방식의 원리와 가압시스템의 특성을 기술한다. 또한 가압시스템의 구성요소인 열교환기의 형상과 구조 및 각 열교환기의 특징에 대하여 설명한다. 본 자료는 발사체 개발단계에서 가압시스템의 기본요구조건 도출과 개념설계 단계에서 활용할 수 있다.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.3022-3029
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• 2015

본 연구에서는 물과 비 혼합 비 공비 물질을 작동 유체로 사용하는 가시화 실험 장치를 제작하여 열유속을 증가시키며 시간에 따른 벽면온도 특성과 내부 유동를 카메라로 연속 촬영하며 2유체 열사이폰의 내부의 유동 및 열전달 특성에 대하여 가시적 방법으로 실험을 수행하여 실험 결과로부터 다음과 같은 결론을 얻을 수 있었다. 물과 FC40을 사용한 비 혼합 2유체 열사이폰은 열유속의 크기에 따라 자연대류, 펄스비등, 연속비등의 세가지 영역으로 구분 되었으며 비등은 증기압이 낮은 물에서 발생하였다. 자연대류에서는 액체 풀에서 물의 증발과 대류 액막 유동이 발생하였다. 액체 풀에서 비등이 발생할 때에는 강한 비등에 의하여 FC40과 물의 혼합된 상태로 전 영역에 걸쳐 기-액 이상 유동이 발생하였다.

• 한국대기환경학회지
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• 제29권5호
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• pp.634-641
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• 2013

Condensing species behaviour downstream of a combustor was discussed with particle size distribution in this study. The effects of operating conditions in a biomass combustion facility, i.e. concentration of condensing species, temperature gradient, residence time and injection of adsorbents, on particle size distribution were investigated. Pyroligneous liquid which was completely vaporized at the temperature higher than $350^{\circ}C$ was used as a representative of condensing gaseous species. We found that particle size downstream of a combustor increased with increasing heating temperature (i.e. concentration of condensing species) and residence time. However, temperature gradient was not an important factor to control the particle size. The addition of $SiO_2$ precursor as an adsorbent could effectively prevent the particle formation by adsorbing condensing gaseous species on $SiO_2$ particles, and increased the particle size up to 300 nm, resulting in increasing particle removal efficiency in a conventional air pollution control device.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1637-1641
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• 2003

Korea Gas Corporation(KOGAS) is a Liquified Natural Gas(LNG) supplier through out the Korea. LNG, which is imported wholly from foreign countries, is compressed 1/600 for easy transportation and is stored in a liquid state in the storage tanks at Incheon, Pyeongtaek and Tongyeong. At LNG receiving terminals, LNG is vaporized to natural gas before supplying to City Gas Consumer of Power Plant. The secondary pump is a equipment which compress LNG from 1- kgf/cm2 to 70 kgf/cm2. The secondary pump at Tongyeong LNG receiving terminal is consisted of two pumps in one underground PIT, and is connected to supporting structures. It is therefore expected that there is a vibration problem whit the pump and was found that high level vibration was occurred in a low frequency band($5^{\sim}10Hz$). In this paper, the vibration of secondary pump was analyzed, and the main cause of vibration was found out.

• 한국세라믹학회지
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• 제31권9호
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• pp.1037-1043
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• 1994

The effects of annealing atmosphere and temperature on piezoelectricity (k33) and the mechanical strength of machined PZT was studied. Morphotropic Nb-doped PZT was sintered, machined to a rod and then annealed between 80$0^{\circ}C$ and 100$0^{\circ}C$ in air, PbZrO3, and CuO atmospheres respectively. In air or PbZrO3 atmosphere, the compressive strength of Nb-doped PZT increased by 12% with little change in k33 irrespective of annealing temperature. In CuO atmosphere, on the other hand, the compressive strength increased by 20% with little change in k33 at 80$0^{\circ}C$ but both turned to significant decrease above 90$0^{\circ}C$. The examination of the phase distribution and microstructure beneath the surface of CuO-treated PZT revealed that the changes in compressive strength and k33 are closely related to the reaction between PZT and vaporized CuO:liquid PbO precipitated in shallow surface region by the substitution of Cu to Pb sites enhances the decrease in microcracks and the surface roughness at 80$0^{\circ}C$ ; rapid evaporation of precipitated PbO expands a porous region of changed composition into the bulk above 90$0^{\circ}C$.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.741-747
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• 2010

발사체의 추진공급시스템에 사용되는 벤트/릴리프밸브는 안전밸브의 조합체로 극저온의 산화제를 주입할 때와 비행 중에 기화된 산소기체를 배출시킨다. 벤트/릴리프밸브의 설계검증을 위해 AMESim과 FLUENT 상용코드를 이용하여 밸브모델을 구성하였다. AMESim 밸브모델을 검증하기 위해 밸브의 개폐압력, 개폐작동시간을 수학적 계산결과와 비교하였고 내부유동해석 결과를 반영하여 모델의 정확도를 높였다. 본 연구에서는 설계인자를 검증 및 작동성능을 분석하였다. 이 결과는 한국형 발사체에 사용되는 다양한 규격의 벤트/릴리프밸브 개발과정의 효율성을 높일 수 있을 것으로 판단된다.