• International Journal of Automotive Technology
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• 제7권5호
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• pp.585-593
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• 2006

The effect of the shape of the side wall on vaporization and fuel mixture were investigated for the impinging spray of a direct injection(DI) gasoline engine under a variety of conditions using the LIEF technique. The characteristics of the impinging spray were investigated under various configurations of piston cavities. To simulate the effect of piston cavity configurations and injection timing in an actual DI gasoline engine, the parameters were horizontal distance from the spray axis to side wall and vertical distance from nozzle tip to impingement plate. Prior to investigating the side wall effect, experiments on free and impinging sprays for flat plates were conducted and these results were compared with those of the side wall impinging spray. For each condition, the impingement plate was located at three different vertical distances(Z=46.7, 58.4, and 70 mm) below the injector tip and the rectangular side wall was installed at three different radial distances(R=15, 20, and 25 mm) from the spray axis. Radial propagation velocity from spray axis along impinging plate became higher with increasing ambient temperature. When the ambient pressure was increased, propagation speed reduced. High ambient pressures tended to prevent the impinging spray from the propagating radially and kept the fuel concentration higher near the spray axis. Regardless of ambient pressure and temperature fully developed vortices were generated near the side wall with nearly identical distributions, however there were discrepancies in the early development process. A relationship between the impingement distance(Z) and the distance from the side wall to the spray axis(R) was demonstrated in this study when R=20 and 25 mm and Z=46.7 and 58.4 mm. Fuel recirculation was achieved by adequate side wall distance. Fuel mixture stratification, an adequate piston cavity with a shorter impingement distance from the injector tip to the piston head should be required in the central direct injection system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.774-778
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• 2004

The atomization process of a circular $SF_{6}$ liquid jet issued into an otherwise quiescent, high-pressure $N_2$ gas was observed to explore the breakup mechanism of liquid ligaments involved in turbulent atomization. Both liquid and gas temperatures were fixed at a room temperature but the gas pressure was elevated to more than twice the critical pressure of $SF_{6}$. Therefore, the liquid surface was in a thermodynamic state close to a critical mixing condition with suppressed vaporization. Since the surface tension and the surface gas density approach zero and the surface liquid density, respectively, phenomena equivalent to those which would appear when a very high speed laminar flow of water were injected into the atmospheric-pressure air can be observed by issuing $SF_{6}$ liquid at low speeds in micro-gravity environment which avoid disturbances due to gravity forces. The instability ob near-critical mixing surface jet was quantitatively characterized using a newly developed device, which could issue a very small amount of $SF_{6}$ liquid at small constant velocity into a very high-pressure $N_2$ gas.

• 한국분무공학회지
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• 제4권3호
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• pp.15-23
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• 1999

The use of LPG as clean fuel for Diesel engine is very attractive way to reduce soot and NOx emission. In this study, a numerical study has been done to know the transient behavior of LPG fuel in chamber pressures which is held at a pressure above (0.37MPa)and below(0.15MPa)the fuel vapor pressure. Results show that the vortex formed within the start of injection at the leading edge of the spray cone and was most apparent for 0.15MPa chamber pressure case. The high speed photographs and model results showed a narrower cone angle during the quasi-steady spray period at the 0.37MPa chamber pressure compared to the 0.15MPa case. And it can be shown that more realistic vaporization process is necessary to predict the spray length well.

• 한국분무공학회지
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• 제13권2호
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• pp.91-98
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• 2008

In the present study, in order to understand the overall spray combustion characteristics of DME fuel as well as to identify the distinctive differences of DME combustion processes against the conventional hydrocarbon liquid fuels, the sequence of the comparative analysis have been systematically made for DME and n-heptane liquid fuels. To realistically represent the physical processes involved in the spray combustion, this studyemploys the hybrid breakup model, the stochastic droplet tracking model, collision model, high-pressure evaporation model, and transient flamelet model with detailed chemistry. Based on numerical results, the detailed discussions are made in terms of the autoignition, spray combustion processes, flame structure, and turbulence-chemistry interaction in the n-heptane and DME fueled spray combustion processes.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.972-980
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• 2006

In general, to send out natural gas via a pipeline network across the nation in LNG terminal, high-pressure cryogenic pump supply highly compressed LNG to high-pressure vaporization facilities. The Number of cryogenic pumps determined the send-out amount in LNG receiving terminal. So it is main equipment at LNG production process and should be maintained on best conditions. In this paper, to find out the cause of high vibration at cryogenic pumps-motor system in LNG terminal, vibration spectrum analysis and motor current signature analysis have been performed together. Through the analysis, motor rotor bar problems are estimated by the vibration analysis and confirmed by the current analysis. So, it is demonstrated through the case study in this paper, how performing vibration analysis and current signature analysis together can reliable diagnosis rotor bar problems in pump-motor system.

• 동력기계공학회지
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• 제12권6호
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• pp.64-69
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• 2008

The spatial fuel distribution of the stratified charge of a high pressure 6-hole injector was examined in a single cylinder optical direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF(Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played more effective role in the spatial fuel distribution of the stratified charge than the swirl flow during the compression stroke and the fuel distribution area increased due to the activation of the fuel vaporization by the increase of the coolant temperature. But, the increase of the fuel supplying pressure could not change the pattern of the fuel vapor distribution against the expectation.

• 방사성폐기물학회지
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• 제16권4호
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• pp.479-490
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• 2018

본 연구에서는 심부시추공 처분을 위한 밀봉시스템으로서 Gibb's Group에 의해 제안된 화강암 용융 및 재결정화에 의한 시추공 밀봉 방안에 대해 KURT 화강암을 대상으로 실현 가능성을 확인하였다. 화강암 용융 실험은 첨가제를 이용한 상압 용융시험과 물의 기화에 의한 수증기 고압용융시험 2가지로 수행되었다. 상압 용융시험 결과, KURT 화강암 분말에 NaOH를 첨가하여도 기본 융점보다 낮은 $1,000^{\circ}C$에서 부분용융이 시작되었으며, 냉각된 용융물에서 침상결정의 형성을 확인하였다. 수증기 고압시험은 물의 첨가량에 따라 수증기압을 달리하며 최대 400 bar의 수증기압까지 용융 시험이 진행되었다. KURT 화강암은 낮은 수증기압에도 $1,000^{\circ}C$에서 부분 용융이 시작되었으나, 물이 많이 첨가된 높은 수증기압에서 화강암의 부분 용융은 보이지 않았다. 따라서 소량의 수증기가 있는 고압상태가 화강암의 용융에 적합한 것으로 판단되었다. 한편, 고온고압의 수증기는 내부식성의 반응기 벽을 부식시켜, 고온의 수증기에 의한 처분용기의 부식 문제가 발생되었다.

• 동력기계공학회지
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• 제18권6호
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• pp.186-192
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• 2014

The spray structures under the stratified and homogeneous charge condition of a gasoline direct injection were investigated in a visualized constant volume chamber. The chamber pressure was controlled from 0.1 MPa to 0.9 MPa by the high pressure nitrogen and the chamber temperatures of $25^{\circ}C$, $60^{\circ}C$ and $80^{\circ}C$ were controlled by the band type heater. The fuel, iso-octane was injected by a 6-hole injector with the pressures of 7 MPa and 12 MPa. From the experiments results, it is confirmed that at lower chamber pressure, the penetration length and spray angle are mainly affected by the chamber temperature with the vaporization of the fuel droplets and generated vortices at the end region of the spray. And at higher chamber pressure, the penetration lengths at the end of the injection were about 50~60% of that at lower chamber pressure regardless of the chamber temperature and the effect of fuel injection pressure is larger than that of the chamber temperature which results from larger penetration lengths at higher fuel injection pressure than at lower fuel injection pressure regardless of the chamber temperatures.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.120-131
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• 2005

The evaporation characteristics of single and multicomponent droplets hanging at the tip of a quartz fiber are studied experimentally at the different environmental conditions under normal gravity. Heptane and Hexadecane are selected as two fuels with different evaporation rates and boiling temperatures. At the first step, the evaporation of single component droplet of both fuels has been examined separately. At the next step the evaporation of several blends of these two fuels, as a binary component droplet, has been studied. The temperature and pressure range is selected between 400 and 700 $^{\circ}C$, and 0.1 and 2.5 MPa, respectively. High temperature environment has been provided by a falling electrical furnace. The initial diameter of droplet was in range of 1.1 and 1.3 mm. The evaporation process was recorded by a high speed CCD camera. The results of binary droplet evaporation show the three staged evaporation. In the the first stage the more volatile component evaporates. The droplet temperature rises after an almost non evaporating period and in the third stage a quasi linear evaporation takes place. The evaporation of the binary droplet at low pressure is accompanied with bubble formation and droplet fragmentation and leads to incomplete microexplosion. The component concentration affects the evaporation behavior of the first two stages. The bubble formation and droplet distortion does not appear at high environment pressure. Nomenclature

• Journal of Welding and Joining
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• 제16권1호
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• pp.52-62
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• 1998

Laser beam welding of zinc-coated steel, especially lap joints, has a problem of zinc vapor produced during welding which has a low vaporization temperature of 906.deg. C. It is lower than the melting temperature of steel (1500.deg. C). The high pressure formed by vaporization of zinc during laser welding splatters the molten pool and creates porosities in weld. During laser lap welds of zinc-coated steel sheets with CW CO$_{2}$ laser the gap size has been analyzed and simulated using a FEM. The simulation has been carried out in the range of gap aetween 0 and 0.16 mm. The vaporized zinc gas has effected to prevent heat from conducting toward the bottom of sheets. In vaporized zinc gas has effected to prevent heat from conducting toward the bottom of sheets. In the case of too small gap size, zinc gas has not ejected and existed between two sheets. Therefore heat was difficult to conduct from the upper sheet to lower sheet and the upper sheet could over-melted. In the case of large gap size the zinc gas has been prefectly ejected but only a part of lower sheet has melted. The optimum range of gap size in the lap welds of zinc-coated steel sheets has been calculated to be between 0.08 and 0.12 mm. According to the comparison of experiment, the simulation is proved to be acceptable and applicable to laser lap welds.