• Title/Summary/Keyword: high temperature high pressure

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An Experimental Study on Spray Characteristics of Diesel and Bio-diesel Fuel (디젤 및 바이오디젤 연료의 분무특성에 관한 연구)

  • Kim, Jae-Duk;Ainull, Ghurri;Song, Kyu-Keun;Jung, Jae-Yeon;Kim, Hyung-Gon
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.1
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    • pp.53-59
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    • 2011
  • The using of diesel engine will be increased in the world for fuel economy. But diesel engine emits harmful emissions such as much NOx, smoke etc. In this study, experiments were performed to investigate the spray characteristics of diesel spray in a common-rail system according to fuel temperature, injection pressure, injection period and fuel viscosity etc. using a high speed video camera. Diesel oil has different spray patten due to injection pressure and injection period in a common-rail system. A Filter pressure was influenced by fuel temperature which was turned to fuel viscosity related to a fluid flowing. The effect of the bio-diesel fuel mixing ratio on the spray and atomization characteristics was also investigated at various experimental conditions. It shows that the droplet atomization characteristics of bio-diesel fuel showed deteriorated results as the mixing ratio of biodiesel increased because of the high viscosity.

Morphological study of $SF_6$ clathrate hydrate crystal ($SF_6$ 하이드레이트 결정 성장의 특성)

  • Lee, Yoon-Seok;Lee, Hyun-Ju;Lee, Eun-Kyung;Kim, Soo-Min;Lee, Ju-Dong;Kim, Yang-Do
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.711-711
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    • 2009
  • Global warming has been widely recognized as a serious problem threatening the future of human beings. It is caused by the buildup in the atmosphere of greenhouse gases, such as carbon dioxide, methane, hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6). Particularly, SF6 has extremely high global warming potential compare to those of other global warming gases. One option for mitigating this greenhouse gas is the development of an effective process for capturing and separating these gases from anthropogenic sources. In general, gas hydrates can be formed under high pressure and low temperature. However, SF6 gas is known to form hydrate under relatively milder conditions. Therefore, technological and economical effects could be expected for the separation of SF6 gas from waste gas mixtures. In this study, we carried out morphological study for the SF6 hydrate crystals to understand its formation and growth mechanisms. The observations were made in high-pressure optical cell charged with liquid water and SF6 gas at constant pressure and temperature. Initially SF6 hydrate formed at the surface between gas and liquid regions, and then subsequent dendrite crystals grew at the wall above the gas/water interface. The visual observations of crystal nucleation, migration, growth and interference were reported. The detailed growth characteristics of SF6 hydrate crystals were discussed in this study.

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An Experimental Study on Expansion of Operation Range by Lean Boosting for a HCCI H2 Engine (희박과급에 의한 수소 예혼합 압축착화 기관의 운전영역 확장에 관한 실험적 연구)

  • Ahn, Byunghoh;Lee, Jonggoo;Lee, Jongmin;Lee, Jongtai
    • Journal of Hydrogen and New Energy
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    • v.24 no.6
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    • pp.573-579
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    • 2013
  • Hydrogen engine with homogeneous charged compression ignition can achieve high efficiency by high compression ratio and rapid chemical reaction rates spatially. However, it needs to expansion of the operation range with over-all load conditions which is very narrow due to extremely high pressure rise rate. The adoption of the lean boosting in a HCCI $H_2$ engine is expected to be effective in expansion of operation range since minimum compression ratio for spontaneous ignition is decreased by low temperature combustion and increased surround in-cylinder pressure. In order to grasp its possibility by using lean boosting in the HCCI $H_2$ engine, compression ratio required for spontaneous ignition, expansion degree of the operation range and over-all engine performance are experimentally analyzed with the boosting pressure and supply energy. As the results, it is found that minimum compression ratio for spontaneous ignition is down to the compression ratio(${\varepsilon}$=19) of conventional diesel engine due to decreased self-ignition temperature, and operation range is extended to 170% in term of the equivalence ratio and 12 times in term of the supply energy than that of naturally aspirated type. Though indicated thermal efficiency is decreased by reduced compression ratio, it is over at least 46%.

Growth of zinc oxide thin films by oxygen plasma-assisted pulsed laser deposition

  • Pak, Sang-Woo;Suh, Joo-Young;Lee, Dong-Uk;Kim, Eun-Kyu
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.208-208
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    • 2010
  • Zinc oxide (ZnO) is a functional material with interesting optical and electrical properties, a wide band gap (more than 3.3 eV), a high transmittance in the visible light region, piezoelectric properties, and a high n-type conductivity. This material has been investigated for use in many applications, such as transparent electrodes, blue light-emitting diodes, and ultra-violet detector. ZnO films grown under low oxygen pressure by thin film deposition methods show low resistivity and large free electron concentration. Therefore, reducing the background carrier concentration in ZnO films is one of the major challenges ahead of realizing high-performance ZnO-based optoelectronic devices. In this study, we deposited ZnO thin films on sapphire substrates by pulsed laser deposition (PLD) with employing an oxygen plasma source to decrease the background free-electron concentration and enhance the crystalline quality. Then, the substrate temperature was varied between 200 'C to 900 'C The vacuum chamber was initially evacuated to a pressure of $10^{-6}$ Torr, and then a pure $O_2$ gas was introduced into the chamber and the pressure during deposition was maintained at $10^{-2}$ Torr. Crystallinity and orientation of ZnO films were investigated by X-ray diffraction (XRD). The film surface was analyzed with atomic force microscope (AFM). And electrical properties were measured at room temperature by Hall measurement.

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A Study on Characteristics of Durability for Plunger of High Speed and Ultra-High Pressure Reciprocating Pump Using High Velocity Oxygen Fuel Spraying (초고속 용사 적용 고속 초고압 왕복동 펌프 플런저의 내구성 특성에 관한 연구)

  • Bae, Myung-Whan;Park, Byoung-Ho;Jung, Hwa;Park, Hui-Seong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.5
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    • pp.20-28
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    • 2014
  • The high velocity oxygen fuel spraying (HVOF) is a kind of surface modification process technology to form the sprayed coating layer after spraying the powder to molten or semi-molten state by the ultra-high speed at the high-temperature heat source and conflicting with a substrate. It is desirable to melt completely the thermal spray powder in order to produce the coating layer with an optimal adhesion, however, because a semi-molten powder in a spray process has the low efficiency and become a factor that degrades the mechanical property by the inducement of pore-forming within the coating layer. To improve the wear resistance, corrosion resistance and heat resistance, in this study, the plungers of high-speed and ultra-high pressure reciprocating hydraulic pumps for oil and water used in ironwork are produced with $420J_2$ and the coating layers of plungers are formed by the powders of WC-Co-Cr and WC-Cr-Ni including the high hardness WC. The surface of these plungers is modified by the super-mirror face grinding machine using variable air pressure developed in this laboratory, and then the characteristics of cross-sectional microstructure, and surface roughness and hardness values between no operation and 100 days-operation are examined and made a comparison. The fine tops and bottoms on surface roughness curve of oil-hydraulic pump plunger sprayed by WC-Cr-Ni are molded more and higher than those of water-hydraulic pump sprayed by WC-Co-Cr because the plunger diameter of oil-hydraulic pump is 0.4 times smaller than that of water-hydraulic pump and the pressure of oil-hydraulic pump exerted on the plunger is operated with the 70 bars higher than that of water-hydraulic pump. As a result, it is found that the values of centerline average surface roughness and maximum height for oil-hydraulic pump plunger are bigger than those of water-hydraulic pump plunger.

An Experimental Study on the Energy Separation in the Ratio of Nozzle Area of a tow Pressure Vortex Tube (저압용 보텍스튜브의 노즐면적비에 따른 에너지 분리특성에 관한 실험적 연구)

  • 오동진;최정원
    • Journal of Energy Engineering
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    • v.13 no.1
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    • pp.34-39
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    • 2004
  • The process of energy separation in a low pressure vortex tube with compressed air as a working medium is studied in detail. Experimental data of the temperature of the cold and hot air leaving the vortex tube are presented. The variation of the maximum wall temperature along the inner surface of a vortex tube and the temperature distribution in a vortex tube provide useful information about the location of the stagnation point of the flow field at the axis of the vortex tube Analysis of the results enabled to find the optimum ratio of nozzle area and the optimum shape of an orifice. From this optimum geometric setup of a low pressure and big vortex tube the effectiveness of energy separation was better than a high pressure and small vortex tube.

Sea Level Variations at Kerguelen Island in the South Indian Ocean by the Satellite Data(ARGOS) and Meteorological Data(METEO)

  • Yoon, Hong-Joo
    • Korean Journal of Remote Sensing
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    • v.16 no.2
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    • pp.117-133
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    • 2000
  • We studied the sea level variations at Kerguelen island in the South Indian Ocean with ARGOS data and meteorological data during about 1 year(May 1993~April 1994) through using filter, spectral analysis, coherency and phase, and found characteristics for the two oceanic signal levels(detided oceanic signal level, h$_{detided}$ and seasonal oceanic level, h$_{corr.ib}$). The forms of atmospheric pressure variations are good agreed to between ARGOS data and meteorological data in the observed periods. This Kerguelen area shows the inflow of an air temperature(gain of a radiant heat) into the sea water and the stagnation of high atmospheric pressure bands in summer, and the outflow of a sea water temperature(loss of sensible and latent heat) toward the atmosphere and the stagnation of low atmospheric pressure bands in winter. The seasonal difference of sea level between summer and winter is about 1.6cm. Both the detided oceanic signal level(h$_{detided}$) variation and the inverted barometer level(h$_{ib}$) variation have a strong correlation for T>1day period bands. The characteristics of h$_{detided}$ variation are not decided by the influence of any meteorological distributions (atmospheric pressure), but the influence of other factors(bottom water temperature) for T>2days periods bands. h$_{corr.ib}$ plays a very important role of sea level variation in the observed periods (especially T>about 180days period bands).

Spontaneous Steam Explosions Observed In The Fuel Coolant Interaction Experiments Using Reactor Materials

  • Jinho Song;Park, Ikkyu;Yongseung Sin;Kim, Jonghwan;Seongwan Hong;Byungtae Min;Kim, Heedong
    • Nuclear Engineering and Technology
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    • v.34 no.4
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    • pp.344-357
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    • 2002
  • The present paper reports spontaneous steam explosions observed in fuel coolant interaction experiments using prototypic reactor materials. Pure ZrO$_2$ and a mixture of UO$_2$ and ZrO$_2$ are used. A high temperature molten material in the form of a jet is poured into a subcooled water pool located in a pressure vessel. An induction skull melting technique is used for the melting of the reactor material. In both tests using pure ZrO$_2$ and a mixture of UO$_2$ and ZrO$_2$, either a quenching or a spontaneous steam explosion was observed. The morphology of debris and pressure profile clearly indicate the differences between the qunching cases and explosion cases. The dynamic pressure. dynamic impulse, water temperature, melt temperature, and static pressure Inside the containment chamber were measured . As the spontaneous steam explosion for the reactor material is firstly observed in the present experiments, the results of present experiments could be a siginificant step forward the understanding the explosion of the reactor material.

Numerical Analysis on Depressurization of High Pressure Carbon Dioxide Pipeline (고압 이산화탄소 파이프라인의 감압거동 특성에 관한 수치해석적 연구)

  • Huh, Cheol;Cho, Meang Ik;Kang, Seong Gil
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.19 no.1
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    • pp.52-61
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    • 2016
  • To inject huge amount of $CO_2$ for CCS application, high pressure pipeline transport is accompanied. Rapid depressurization of $CO_2$ pipeline is required in case of transient processes such as accident and maintenance. In this study, numerical analysis on the depressurization of high pressure $CO_2$ pipeline was carried out. The prediction capability of the numerical model was evaluated by comparing the benchmark experiments. The numerical models well predicted the liquid-vapor two-phase depressurization. On the other hands, there were some limitations in predicting the temperature behavior during the supercritical, liquid phase and gaseous phase expansions.

A Study on the Preocessing of high Runctional Composites and the Evaluation of Its Characteristics (고기능성 복합재료의 제조와 그 특성평가에 관한 연구)

  • 김윤해
    • Journal of Advanced Marine Engineering and Technology
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    • v.22 no.2
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    • pp.139-145
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    • 1998
  • Filament winding method is widely used for composite fabrications using low viscosity liquid for-mation and processing asymmetrical structures of pressure vessel pipe rocket motor case etc. The filament winding method is affected by several parameters such as pot life of process time viscosi-ty of resin filament winding temperature and schedules curing condition and post curing condi-tion of resin. To develope high functional composite materials the rotation(5, 15, 20, 30rpm) of the winding machine was controlled by D.C motor. And the wiper to give proper tension was equipped between strand and resin bath. The resin is hooked by the design wiper. The adequate cure schedule was found by DSC. NOL ring test is carried out to investigate the basic physical properties such as design technology. The void contents in filament winding is generally higher than that of the prepreg laminated plate. These high contents of void can make a crack in resin in spite of low deformation. These problem was solved by giving tension in processing. To improve the characteristics of fiber volume fraction void contents resin/fiber bonding the winding speedc is changed under constant tension. It was found that resin impregnation was not different from in fiber contents void contents at the range of 0.5~1kg tension but it was found that resin was not impregnated at the above of 1.5kg tension. In burst test a pure PE liner was failed at a nozzle part under the $14kg/\textrm{cm}^2$ pressure but a pressure vessel of CNG was failed at a cylinder part under the $200kg/\textrm{cm}^2$ pressure.

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