• Title/Summary/Keyword: high temperature high pressure

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The Effects of Niobium on Sliding Wear Characteristics of High Speed Steel by Powder Metallurgy (분말고속도공구강의 미끄럼마모특성에 미치는 Nb의 영향)

  • 이한영;배종수;김용진
    • Tribology and Lubricants
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    • v.16 no.3
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    • pp.194-200
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    • 2000
  • In order to evaluate the effect of Nb on wear properties of high speed steel(HSS) by powder metallurgy, niobium-alloyed HSS have been prepared by adding 0%, 1%, 3% and 5%Nb to HSS of 6%W-5%Mo-4 %Cr-5%V-5%Co. Sliding wear tests were conducted at various sliding speed conditions under the constant pressure using a pin-on-disc type machine. The results of this study show that the wear resistance of HSS by powder metallurgy was increased by the addition of Nb within the range of sliding speed used in this experimental study. However, the amount of Nb did not improve the wear resistance. It may be due to the thermal stability of carbide and high temperature properties of the matrix containing Nb comparing to that without Nb.

Innovative Modeling and Simulation of Reacting Flow with Complex Confined Boundaries

  • Kim, Ki-Hong;Yoh, Jai-Ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.311-319
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    • 2008
  • We present an innovative method of multi physics application involving energetic materials. Energetic materials are related to reacting flows in extreme environments such as fires and explosions. They typically involve high pressure, high temperature, strong shock waves and high strain rate deformation of metals. We use an Eulerian methodology to address these problems. Our approach is naturally free from large deformation of materials that make it suitable for high strain rate multi-material interacting problems. Furthermore we eliminate the possible interface smearing by using the level sets. We heave devised a new level set based tracking framework that can elegantly handle large gradients typically found in reacting gases and metals. We show several work-in-progress application of our integrated framework.

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A Study on Pore Pressure Evaluation of Concrete Lining in Road Tunnel Fire (도로터널 라이닝 화재조건 콘크리트 라이닝 공극압력 특성에 관한 연구)

  • Park, Kyung-Hoon;Kim, Heung-Youl;Yoo, Yong-Ho;Lee, Chul-Ho;Kim, Hyung-Jun
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 2008.11a
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    • pp.484-489
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    • 2008
  • We carried out a one-way heating experiment on the PC panel manufactured by changing the filling depths(20,30,40,50mm) of concrete regarding the fire strength in order to measure the inner concrete pressure which is a direct cause of concrete spalling. This fire experiment was conducted under the fire strength conditions of ISO 834 Standard, Modified Hydrocarbon and the maximum value of Pore Pressure was measured. As a result of analyzing the time it took to reach maximum pressure, it showed that the time rising to the maximum pressure of high strength concrete of 40MPa is slower than that of a 24MPa tunnel lining. In case of ISO fire conditions, spalling damage might take place in heating period of $20{\sim}40$ minutes in the range of $100{\sim}200^{\circ}C$ temperature. In case of MHC fire conditions, the area damaged by fire can appear after a lapse of $25{\sim}50$ minutes in the range of $150{\sim}250^{\circ}C$ temperature.

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A Study on the Expansion Cavity Pipe for Performance Improvement of Exhaust System in Automotive (자동차 배기성능개선을 위한 확장형 공동파이프에 관한 연구)

  • Son, Sung-Man;Park, Kyoung-Suk
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.5
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    • pp.1-6
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    • 2009
  • The temperature of exhaust gas was raised by increasing of engine movement on developing engine. Thermal of high temperature and pressure reverse in bellows, because of increasing of engine movement and the thermal performance of converter in combustion. As a result, thermal loss is increased and thermal efficiency is decreased rapidly in bellows, it can occur to damage in mechanical structure. In this study, it was necessary to analyze back pressure performance and thermal characteristic on driving condition in exhaust system. It was adapted braid type bellows and straight type exhaust pipe. It was compared with curve type exhaust pipe for lay-out on considering to design of exhaust system. It was necessary to improve thermal characteristic and back pressure performance so that expansion cavity pipe(ECP) was installed between bellows and catalyst convert. Not only decreasing back pressure was solved but also thermal characteristic problems in exhaust pipe because of increasing capacity. According to this study, the basis of data is presented when new exhaust system is designed.

A Study on the Disc Design of a Safety-valve for the Specialized Pressure-vessel Considering Thermal Expansion (열팽창을 고려한 특수 압력용기용 안전밸브 디스크의 설계에 관한 연구)

  • Kang, Jae-Won;Kim, Chang-Ho;Kang, Dong-Ho
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1581-1584
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    • 2007
  • The safety valve is the important equipment used to protect the pressure vessel and pressure facilities from overpressure by discharging the operation medium when the pressure of system is reaching the design pressure of the system. Some materials for a safety valve disk are studied in this paper. A studied safety valve has to resist sulfurous acid and nitric acid. etc. Furthermore teflon which is a general material of the valve easily sticks to a disk and a sliding part of the valve by thermal expansion. Therefore both teflon and stainless-steel are used to improve these problems. The analysis of the thermal expansion is conducted with commercial FEM software to improve the problems. Boundary conditions were temperature and load in this study. From the analysis, the thermal expansion of by teflon/stainless steel-made valve is lower than that of teflon-made valve under high temperature. Thus, teflon/stainless steel-made valve is safe and no malfunction by thermal expansion.

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Preparation of FeB by SHS (Self Propagating High Temperature Synthesis) (자전연소합성법에 의한 FeB 분말의 제조)

  • Shin, Chang-Yun;Won, Chang-Whan
    • Journal of the Korean Ceramic Society
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    • v.45 no.7
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    • pp.418-422
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    • 2008
  • The preparation of FeB by SHS in $B_2O_3-Mg-Fe-Fe_3O_4$ system was investigated in this study. In the preparation of FeB, the effects of the initial pressure of inert gas in reactor, the content of Mg and $Fe_3O_4$ in mixture on the reactivity and reaction products was investigated. The minimum initial pressure of inert gas in reactor for SHS reaction in this system was 25 atm, and as the pressure increased, the concentration of unreacted Mg decreased and combustion temperature increased. At the initial inert gas pressure in reactor of 25 atm, the optimum composition for the preparation of pure FeB was $1.5B_2O_3$+3.43Mg+ 1.7Fe+$0.1Fe_3O_4$. The FeB synthesized in this condition had an irregular shape and the particle size of $5\;{\mu}m$.

Effect of Hydrogen Partial Pressure Ratio on Electrical and Structural Properties of ZnO Thin Film (ZnO 박막의 전기적 구조적 특성에 미치는 수소 분압비의 영향)

  • Lee, Sung-Hun;Shin, Min-Geun;Byon, Eung-Sun;Kim, Do-Geun;Jeon, Sang-Jo;Koo, Bon-Heun
    • Journal of Surface Science and Engineering
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    • v.39 no.6
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    • pp.250-254
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    • 2006
  • Effect of hydrogen partial pressure ratio on the structural and electrical properties of highly c-axis oriented ZnO films deposited by oxygen ion-assisted pulsed filtered vacuum arc at a room temperature was investigated. The hydrogen partial pressure ratio were $1.4%\sim9.8%$ at 40% oxygen pressure ratio. The conductivity of ZnO:H films was increased from 1.4% up to 4.2% due to relatively high carrier mobility caused by improvement of crystallinity While the conductivity of ZnO:H films were decreased over than 4.2% and (0002) orientation was also deteriorated. The lowest resistivity of ZnO:H films was $2.5{\times}10^{-3}\;{\Omega}{\cdot}cm$ at 4.2% of hydrogen pressure ratio. Transmittance of ZnO:H films in visible range was 85% which is lower than that of undoped ZnO films because of declined preferred orientation.

Pressurized Drop Tube Furnace Tests of Global Gasification Characteristics of Coal (PDTF를 이용한 석탄가스화 특성 실험)

  • 신용승;최상민;안달홍
    • Journal of Energy Engineering
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    • v.8 no.4
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    • pp.560-566
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    • 1999
  • PDTF (Pressurized drop tube furnace) experiments using variations of temperature, oxygen/coal ratio, steam/coal and pressure with Roto coal (Sub A) were performed in order to investigate the effects of these experimental parameters on global gasification characteristics at elevated pressure. The results shows that the gasification at elevated pressure is more profitable than that at atmospheric pressure considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at which maximum cold gas efficiency was appeared ranged from 0.5 to 0.7 g/g. only when the temperature is sufficiently high enough, the raise of steam/coal ratio brings improvement of cold gas efficiency. As the pressure increased, the volume of carbon conversion by heterogeneous reaction increased but the volume of carbon conversion by pyrolysis decreased relatively.

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Improvement of Surface Properties of Ti-6A1-4V Alloy by Low Pressure Carburizing (저압 침탄에 의한 Ti-6Al-4V 합금의 표면 특성 개선)

  • Kim, J.H.;Park, J.D.;Kim, S.W.
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.4
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    • pp.191-196
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    • 2003
  • For improvement of the wear performance of Ti alloy, vacuum-carburizing technique was tried for the first time using propane atmosphere. During the low pressure carburizing carbide was formed at the surface and carbon transfer was occurred from the carbide to the matrix. It was found that: (i) surface hardness increased with the reduction of operating pressure and time; (ii) optimum hardness distribution could be obtained with the proper choice of temperature and carbon flux control; and, (iii) case depth was largely influenced not by time but by temperature. The two steps process was recommended for obtaining thick case depth and high surface hardness of Ti alloy. For the low oxygen partial pressure, it was necessary to introduce additional CO gas to the atmosphere.Grain boundary oxidation and non-uniformity could be prevented.

Pressurized drop tube furnace tests of global gasification characteristics of coal (PDTF를 이용한 석탄가스화 특성 실험)

  • 신용승;최상민;안달홍
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • 1999.05a
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    • pp.23-31
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    • 1999
  • PDTF(Pressurized drop tube furnace) experiments using varied temperature, oxygen/coal ratio, steam/coal ratio and pressure with Roto coal(Sub A) were performed in order to investigate the effects of these experimental parameters on global gasification characteristics at elevated pressure. The results shows that the gasification at elevated pressure is more profitable than that at atmospheric pressure considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at which maximum cold gas efficiency was appeared ranged from 0.5 to 0.7g/g. Only when the temperature is sufficiently high enough, the raise of steam/coal ratio brings improvement of cold gas efficiency. As the pressure increased, the volume of carbon conversion by heterogeneous reaction increased but the volume of carbon conversion by pyrolysis decreased relatively.

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