• Title/Summary/Keyword: 연소 저항성

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High Temperature Combustion Behavior of Carbon/Carbon Composites Coated with SiC (탄화규소로 도포된 탄소/탄소 복합재의 고온 연소거동)

  • Choi, Don-Mook;Kim, Joung-Il
    • Journal of the Korean Society of Hazard Mitigation
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    • v.1 no.1 s.1
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    • pp.127-138
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    • 2001
  • Although Carbon/Carbon Composites(CFRCs) have excellent mechanical properties at high temperature, the disadvantage of combustion in air restricts their applications. Thus a lot of investments have been studied to improve the drawback of CFRCs. In this study, SiC used as a thermal protective coating material possesses almost the same expansion coefficient compared to that of carbon, so SiC was coated on 4D (directional) CFRCs by Pack-Cementation process. For the 4D CFRCs coated with SiC, optical microscopy observations were performed to estimate the coating mechanism involved and TGA tests were also performed to evaluate the improvement of combustion resistance. And their high temperature combustion properties were investigated by the arc torch plasma test. From the results, it is found that the mechanical properties and high temperature combustion properties of the 4D(directional) CFRCs coated with SiC were much better than bare 4D CFRCs.

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Base Drag Characteristics with Exothermic Bleed/Jet (발열성 유출류와 제트를 고려한 기저부 저항 특성)

  • Shin J.R.;Choi J.Y.;Kim C.K.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.05a
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    • pp.327-330
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    • 2006
  • Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base homing process. Overall fluid dynamic process is modeled by Wavier-Stokes equations for reacting flows with two-equation $k-\omega$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

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Ablative Mechanism of SiC Coated Carbon/carbon Composites with Ratio of Oxygen to Fuel at Combusion Test (연소시험에서 산소와 연료 비에 따른 탄화규소로 코팅된 탄소/ 탄소 복합재의 삭마 메커니즘)

  • Zhang, Eun-Hee;Kim, Zeong-Baek;Joo, Hyeok-Jong
    • Applied Chemistry for Engineering
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    • v.18 no.3
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    • pp.227-233
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    • 2007
  • Carbon/carbon (C/C) composites as unique materials possess exceptional thermal resistance with light weight, high stiffness, and strength even at high temperature. However, one serious obstacle for application of the C/C composites is their poor oxidation resistance in high temperature oxidizing environments. SiC coating has been employed to protect the composites from oxidation. This study explored combustion characteristics of 4-directional (4D) carbon/carbon composites using liquid fuel rocket engine to investigate ablative motion of the materials. C/C composites were made of coal tar pitch as a matrix precursor, and heat-treated at $2300^{\circ}C$. Throughout repeated densification process, the density of the material reached $1.903g/cm^3$. After machining 4D C/C composites, the nozzle surface was coated by a SiC layer by pack-cementation method to improve oxidation resistance. Erosion characteristics of SiC-coated C/C composites were measured as function of the ratio of oxygen to fuel. The morphological change of the composites after combustion test was investigated using SEM and erosion mechanism also was discussed.

knock in a spark-ignition engine and octane number of gasoline (스파크 점화 기관의 녹킹과 가솔린의 옥탄가)

  • 전광민
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.1
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    • pp.6-9
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    • 1990
  • 본 고에서는 녹킹현상과 녹킹 발생의 결과, 그리고 녹킹과 연료와의 관계등에 대해 개략적으로 설명하려 한다. 녹킹 발생 유무는 흡입공기상태, 스로틀 열림정도, 연소실 형상, 스파크 점화시기, 화염 전파속도 및 연료의 자연 발화 특성에 관계되며 화염 전파속도와 end-gas에 있는 연로의 반응속도와의 경쟁이라 볼수 있다. 연료의 녹킹 발생에 대한 저항성을 나탄내는 척도가 옥탄가이며 옥탄가가 높을 수록 자연 발화하기 어려우므로 녹킹이 잘 일어나지 않는다.

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Plasma Surface Modification of Electrospun PEI(polyetherimide) Web (전기방사된 PEI(polyetherimide) 웹의 플라즈마 표면개질)

  • 권미연;이승구;추보영;주창환
    • Proceedings of the Korean Fiber Society Conference
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    • 2003.10b
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    • pp.126-129
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    • 2003
  • PEI(polyetherimide)는 고강도, 고탄성율를 가지며 20$0^{\circ}C$에서 연속사용이 가능한 고내열성, 내화학성을 가진 고성능 고분자이다. 우수한 물성과 더불어 성형성도 뛰어나 다양한 제품설계를 할 수 있으며, 특히 연소시 낮은 연기배출율(smoke emission)을 지니며, 고유의 우수한 난연성을 가지고 있다. 또한 광범위한 온도와 주파수대에서 높은 유전율과 전기 저항 특성을 유지할 수 있다. (중략)

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A Study on improving the Reliability of Thrust Measurement System (추력측정장치의 신뢰도 향상 방안에 관한 연구)

  • Kang, Donghyuk;Joo, Seongmin;Kim, Jong-gyu;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.1188-1191
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    • 2017
  • Thrust is one of the crucial performance parameter of a combustion chamber in the combustion chamber development test. So it is very important to measure an accurate thrust. Thrust calibration test was performed to identify the system characteristics, resistance and linearity of a vertical thrust measurement system(TMS) for accurate thrust measurement. It has been found 6.9% ~ 8.6% errors between the measured thrust by TMS calibration equations and theoretical thrust. It has been confirmed that the TMS calibration is necessary to be performed with the propellant lines connected to the combustion chamber for accurate thrust measurement.

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Hydraulic Characteristics of Branching and Merging of Channels in Regenerative Cooling Passage in Liquid Rocket Combustors (채널의 분기 및 병합이 있는 액체로켓 연소기 재생냉각 유로에서의 수력학적 특성)

  • Kim, Hong-Jip;Kim, Seong-Ku;Choi, Hwan-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.11
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    • pp.1087-1093
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    • 2008
  • Regenerative cooling passage to guarantee the thermal survivability in high performance rocket engine combustors could have complex configurations of the branching/merging of channels and flow turning, etc. By applying the classical hydraulic coefficients which can be found in the literature according to the flow conditions, hydraulic characteristics in regenerative cooling passages can be obtained effectively through dividing the pressure loss into friction loss and local resistance loss. Satisfactory agreement has been obtained by comparing the present results with experimental measurement of water flow test. In addition, the present results were in good agreement with CFD results when the actual coolant, kerosene was used. Therefore, the application of the present method is expected to be useful to design regeneratively cooled combustors.

Characterization of $SiO_2-R_2O_3$-RO with compositions changes of $R_2O_3$, RO on Sealant ($SiO_2-R_2O_3$-RO계에서 $R_2O_3$, RO 변화에 따른 밀봉재 특성)

  • Yang, Sang-Jin;Choi, Byung-Hyun;Lee, Mi-Jai;Lee, Hong-Lim;Yoo, Young-Sung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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    • pp.23-23
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    • 2007
  • 고체산화물연료전지(SOFC)는 연료가 갖는 화학에너지를 연소과정 없이, 공기와 $H_2$, CO, $CH_4$와 같은 환원성 가스를 공급받아 $700^{\circ}C-850^{\circ}C$에서 전기화학적 반응을 통하여 직접 전기를 얻는 방식이다. SOFC는 여러장의 단위 셀을 적층하여 스택을 구성하는데, 스택 제조시 단전지에 공급되는 산화, 환원 가스의 누출이나 흡입을 막기 위하여 밀봉재를 사용한다. 이러한 밀봉재는 완벽한 밀봉, 열에 대한 안정성, 충격에 견디는 저항성 등의 기계적인 특성 및 구성요소와의 최소한의 열팽창계수차를 가져야 한다. 따라서 본 연구에서는 $SiO_2-R_2O_3$-RO계에서 $R_2O_3$, RO의 변화에 따른 밀봉 특성 및 열팽창계수에 미치는 영향을 조사하였다.

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Improvement of Boiler Performance on 550 MW Coal Fired Thermal Power Plant via Baffle Plates (다공판 연소가스 유량제어를 통한 석탄화력발전소 보일러 성능 개선)

  • Kim, Chi Ho;Moon, Seung-Jae
    • Plant Journal
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    • v.17 no.1
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    • pp.38-49
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    • 2021
  • In order to increase power plant efficiency, the steam temperature was increased to 610 ℃ which deteriorates the durability of the boiler tube and as the use of low-calorie coal increases the post combustion and delayed combustion phenomenon, the overheating of the final reheater and the tube rupture are becoming frequent. In order to prevent overheating of the final reheater, desuperheater water injection was increased, leading to a decrease in boiler efficiency. In this study install a baffle plate at the back of some overheated tube groups, thereby reduce the temperature of the tube by reducing the amount of combustion gas, and the reduced combustion gas moves to an adjacent place to increase the temperature of other tubes. As a result of the study, the temperature deviation between tubes decreased 1.5. And the heat-reducing injection amount was reduced to 6,929 kg/h and the maximum tube temperature was reduced to 623.4℃ which is 6.6℃ more below than the control standard of 630℃.

Powder Preparation and Electrical and Magnetic Properties of ${La_{0.7}}{Ca_{0.3}}{MnO_3}$by Solution Combustion Method for CMR Applications (용액연소법에 의한 CMR용 ${La_{0.7}}{Ca_{0.3}}{MnO_3}$분말 제조 및 전기.자기적 특성)

  • Lee, Kang-Ryeol;Min, Bok-Ki;Park, Sung
    • Journal of the Korean Ceramic Society
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    • v.38 no.6
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    • pp.551-557
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    • 2001
  • La$_{0.7}$Ca$_{0.3}$MnO$_3$분말을 용액연소법으로 제조하였으며 분말 특성과 CMR에 응용하기 위해 박막의 전기적, 자기적 특성을 조사하였다. 조성과 구조 특성을 XRD와 SEM으로부터 조사하였으며 분말의 하소온도를 TG 분석으로부터 결정하였다. 또한 소결성은 dilatometer에 의해 조사되었으며 분말 특성은 BET에 의해 조사되었다. 소결성이 우수한 분말을 이용하여 스퍼터 타겟으로 제조하였으며 SiO$_2$/Si 기판 위에 스퍼터링한 후, 온도에 따른 four point probe 측정으로 막의 MR비를 측정하였다. VSM (Vibrating Sample Magnetometer)를 이용하여 증착된 막의 온도에 따른 자화율(Magnetization:M)을 측정하였다. 분말 특성으로는 평균입자 크기가 sub-micron 이하로 초미세하고 49.44$m^2$/g의 비표면적 값을 얻을 수 있었으며 고순도의 perovskite 구조를 갖는 La$_{0.7}$Ca$_{0.3}$MnO$_3$분말을 쉽게 얻을 수 있었다. 온도에 따른 저항값의 변화로부터 96K에서 최고의 MR값을 얻을 수 있었으며, 240K에서 강자성체로 전이되었다.로 전이되었다.

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