• 한국세라믹학회지
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• 제33권5호
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• pp.485-494
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• 1996

Silica Aerogels with the density and porosity of 0.1g/cm3 and 96% were synthesized by two different supercri-tical drying processes (i.e additional solvent and intial pressure methods) Isoptopanol was chosen as sol-gel and supercritical drying solvents in order to synthesize aerogels at the lower temperature and pressure because the critical values of isopropanol are lower than those of methanol and ethanol commonly used. The P-V-T relationship of isopropanol was experimentally described for optimizing supercritical drying conditions such as the amount of extra solvent and supercritical drying temperature and pressure. In the addional solvent method monolithic and transparent aerogels were obtained by supercritical drying at 25$0^{\circ}C$ and 900 psing after 40% of the reactor volume was filled with isopropanol. Crack-free aerogels were synthesized at 25$0^{\circ}C$ and 1100~1200 psig by the initial pressure method with an intial nitrogen gas pressure of 400 psig and the isopropanol amount of 5% of the reactor volume.

• 대한기계학회논문집B
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• 제33권6호
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• pp.454-460
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• 2009

To analyze the mixture formation process of evaporating diesel spray is important for emissions reduction in actual engines. Then the effects of change in density of ambient gas on spray structure in high temperature and pressure field have been investigated in this study. The ambient gas density was changed from ${\rho}_a=5.0kg/m^3$ to ${\rho}_a=12.3kg/m^3$ with CVC(Constant Volume Chamber). Also, simulation study by modified KIVA-II code was conducted and compared with experimental results. The ambient temperature and injection pressure are kept as 700K and 72MPa, respectively. The images of liquid and vapor phase in the evaporating free spray were simultaneously taken by exciplex fluorescence method. As experimental results, with increasing ambient gas density, the tip penetration of the evaporating free spray decreases due to the increase in the drag force from ambient gas. The spatial structure of a diesel spray can be verified as 2-regions consisted of liquid with momentum decrease and vapor with large-scale vortex. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• 한국연소학회지
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• 제5권1호
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• pp.67-79
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• 2000

An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swril flow(DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microstructure using thermophoretic sampling particle diagnostic(TSPD) as TEM were carried out. The NOx, $CO_2,\;O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.

• Journal of the Korean Wood Science and Technology
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• 제14권2호
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• pp.21-28
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• 1986

목질물질(木質物質)인 톱밥, 볏짚 그리고 왕겨를 열분해(熱分解)하여 기상물질(氣相物質)을 합성(合成)하기 위해, 석영으로 설계 제작된 반응탑(反應塔)을 사용하였다. 최초의 반응온도 350$^{\circ}C$로부터 열분해(熱分解)와 gasification 반응(反應)이 완결된다고 예상되는 550$^{\circ}C$까지 가열하였다. 촉매가 반응온도에 어떤 영향을 미치는지 조사하기 위해 $K_2CO_3$와 $Na_2CO_3$를 촉매로 사용하였다. 합성(合成) gas chromatograph와 mass spectrometer에 의해 CO, $CO_2$, $CH_4$ 그리고 $CH_3CHO$등인 것으로 판명되었다. 합성(合成) gas의 수율(收率)과 조성(組成)은 반응온도(反應溫度)와 이 반응에 사용되는 촉매에 달려있지만, 톱밥을 시료(試料)로 반응온도 550$^{\circ}C$, $K_2CO_3$를 촉매로 사용한 반응(反應)에서 생성되는 gas 체적(體積)은 1,800$m{\ell}$/g 톱밥에 달한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1358-1362
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• 2005

The Ni-base superalloy GTD-111DS was designed in the 1970s and is widely used as the material of the first stage blade under a severe combination of temperature and pressure in gas turbines. But because GTD-111DS is distributed in the shape of blade and blade has a unique figure and many cooling channels, it is hard to manufacture the test specimen. In this reason, there are little data on the microstructure and mechanical properties of the alloy. Therefore through the microstructure analysis, present paper observed that the shape of $\gamma{'}$ did not change even if aging time was increased but the amount and volume of the deposition of secondary $\gamma{'}\;rose\;and\;secondary\;\gamma{'}\;grew\;among\;primary\;\gamma{'}$. Also, by tensile test for different temperature, there was difference between yield strength and tensile strength in room temperature on heat treatment and extracting region but the more increasing temperature, the more decreasing difference between yield strength and tensile strength.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2000년도 제20회 KOSCO SYMPOSIUM 논문집
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• pp.105-116
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• 2000

An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swril flow(DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microrstructure using thermophoretic sampling particle diagnostic(TSPD) as TEM were carried out. The NOx, $CO_2$,$O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.242-247
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• 2004

An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swirl flow (DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microrstructure using thermophoretic sampling particle diagnostic (TSPD) as TEM were carried out. The NOx, $CO_2$, $O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.

• 대한기계학회논문집B
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• 제21권3호
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• pp.358-370
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• 1997

In the present study, investigations were carried out to obtain data on combustion characteristics of methane gas and hydrogen supplemented methane gas in a constant volume combustion chamber. The main results obtained from the study can be summarized as follows. The maximum combustion pressure increases as the initial pressure and hydrogen supplement rate increase, the total burning time is shorten by lowering the initial pressure and by increasing the hydrogen supplement rate. The maximum flame temperature and NO concentration increase by the initial pressure and hydrogen supplement rate increase. The flame propagation processes in near stoichiometric mixture are propagated with a spherical shape, but in excess rich or lean mixtures are propagated with a elliptical shape. And, they are changed an unstable elliptical shape flame with very regular cells by increasing the hydrogen supplement rate.

• 공업화학
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• 제5권1호
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• pp.105-113
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• 1994

Spherocarb와 Sucrose Char에 의해 흡착된 질소가스의 양은 온도를 77K에서 184K가지 일정하게 유지시키면서, 상대적 압력의 함수로서 측정되었다. 다른 온도에서의 Isotherm은 흡착제를 일정한 온도에서 유지시키면서, 액화질소, iso-펜탄, n-펜탄, 에틸알코올과 iso-프로필 알코올의 Slush bath를 사용하여 얻어졌다. 이 연구의 목적은 BET와 D-R 같은 흡착모델을 사용하여, 실험적 데이타를 분석함으로써, 비표면적과 세공부피에 대한 정보를 얻는데 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제36권6호
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• pp.756-761
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• 2012

천연가스는 $-160^{\circ}C$까지 냉각 및 액화되어 액화천연가스(LNG)가 되고, 이때 LNG의 체적은 천연 가스의 1/600로 줄어든다. 이로 인해 LNG는 수송시에 이점이 있다. 본 연구에서는 천연가스 액화용 초저온 캐스케이드 냉동사이클의 LNG 열교환기내 냉매와 천연가스의 압력강하가 액화사이클에 미치는 영향을 파악한 후, LNG 열교환기 설계시 압력강하에 대한 기준안을 제시하고자 한다. 이를 위해 HYSYS를 이용하여 초저온 캐스케이드 액화사이클 내 LNG 열교환기의 압력강하에 대해서 시뮬레이션을 수행하였다. 그 결과, 초저온 액화사이클의 압축일량과 성능계수(COP)의 증가로부터, LNG 열교환기 내의 압력강하는 50 kPa정도를 기준 설계 압력강하로 설정할 수 있음을 알 수 있었다.