• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.39-48
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• 2018

This study presents optimal design of gas lift considering composition of reservoir oil and injected gas which can affect gas lift performance in offshore oil reservoir. Reservoir simulation was conducted by using reservoir models which were built in accordance with API gravity of oil. The results of simulation reveal that oil production rate is considerably increased by gas lift when the reservoir productivity decrease. As a results of response curve analysis for gas lift using well models, gas injection rate to improve the production rate increases as the API gravity of oil decreases and the specific gravity of injected gas increases. The optimal design of gas lift was carried out using multiple lift valves. Consequently, gas lift can be operated at relatively low injection pressure because of decrease in injection depth in comparison to the single lift valve design. The improved oil production rates were analyzed by coupling between reservoir model and well model. As a results of the coupling, it is expected that natural gas injection in the heavy oil reservoir is the most efficient method for improving oil production by gas lift.

• Journal of the Korean Institute of Gas
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• v.26 no.5
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• pp.1-9
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• 2022

Selection of a suitable artificial lift is important in terms of efficient operation and economics for oil production. In general, process of well design includes the selection of artificial lift, but the oil recovery could be enhanced by use of hybrid system combined with two types of artificial lift method according to reservoir condition for oil production. Electric submersible pump (ESP), as a presentative artificial lift method, is a manner for supplying the pressure in the lower part of oil well by using of a multi-stage centrifugal pump with an electric energy. However, there is a disadvantage that has a limit to the application period because of mechanical defection on ESP. Accordingly, it is possible to reduce the shutdown time of production well by applying the ESP/Gas lift hybrid system, which is to switch to a gas lift when an ESP is defective. This study describes the effect of ESP/gas lift hybrid system compared with ESP method for a onshore horizontal well locating in the of Permian basin, USA. As a result of study, ESP/gas lift hybrid system could make more effective productivity than ESP method. Also, we quantitatively predicted how much economic benefit would be obtained when the hybrid system was applied in the production well.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.551-554
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• 2006

Inhibition of propellant temperature rising in liquid propulsion rocket using cryogenic fluid as a propellant is very important. Especially propellant temperature rising during stand-by after filling and pre-pressurization can bring into cavitation in turbo-pump. One of the method preventing propellant temperature rising in cryogenic feeding system is recirculating propellant through the loop composed of propellant tank, feed pipe, and recirculation pipe. The circulation of propellant is promoted through gas-lift effect by gas injection to lower position of recirculation pipe. In this experiment liquid oxygen and gas helium is used as propellant and injection gas. Under atmospheric and pressurized tank ullage condition, helium injection flow-rate is varied to observe the variation of recirculating flow-rate and propellant temperature in the feed pipe. There is appropriate helium injection flow-rate for gas-lift recirculation system.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.93-100
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• 2009

Intake/exhaust valve timing and exhaust cam lift were changed to control the internal exhaust gas recirculation (IEGR) and combustion phase of homogeneous charge compression ignition (HCCI) engine. To measure the IEGR rate, in-cylinder gas was sampled during from intake valve close to before ignition start. The lower exhaust cam made shorter valve event than higher exhaust cam and made IEGR increase because of trapping the exhaust gas. IEGR rate was more affected by exhaust valve timing than intake valve timing and increased as exhaust valve timing advanced. In-cylinder pressure was increased near top dead center due to early close of exhaust valve. Ignition timing was more affected by intake valve timing than exhaust valve timing in case of exhaust valve lift 8.4 mm, while ignition timing was affected by both intake and exhaust valve timing in case of exhaust valve 2.5 mm. Burn duration with exhaust valve lift 2.5 mm was longer than other case due to higher IEGR rate. The fuel conversion efficiency with higher exhaust valve lift was higher than that with lower exhaust valve lift. The late exhaust and intake maximum open point (MOP) made the fuel conversion efficiency improve.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.7-13
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• 2010

To satisfy the needs on fuel economy and engine performance, continuous variable valve lift systems are applying to engines. In the CVVL system, fuel economy can be improved by reducing pumping loss during the induction process, and engine performance can be also improved by controlling volumetric efficiency and the residual gas fraction. Because the residual gas fraction directly affects volumetric efficiency, engine performance, combustion efficiency and emissions in SI engines, controlling residual gas fraction is one of the important things in engine development process. This analysis investigates the residual gas fraction and volumetric efficiency with changes of intake valve lifts and intake valve timings. In this study, unsteady state solutions were solved during exhaust and induction processes. Results show variation of the residual gas fraction and volumetric efficiency by changing intake valve timing and lift. Decreasing intake valve lift leads to increase the residual gas fraction and to decrease volumetric efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.398-404
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• 1999

The EGR is needed for one of various strategies to reduce NOx emission. But to get the proper EGR rate the intake and exhaust system become complicated. That is a reason why we consider using the built0in EGR system. The built-in EGR is a system which reduces Nox by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust. In this paper characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results the possibility of suing the built-in EGR system was confirmed.

• Microbiology and Biotechnology Letters
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• v.22 no.6
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• pp.659-664
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• 1994

In order to predict gas hold-up and oxygen transfer rate during sisomicin fermentation employing air lift fermentor, simulated media similar to fermentation broths in rheological proper- ties were prepared and used. Rheological properties of fermentation broths from 40 hours and 60 hours of cultivation were analyzed by applying to Power's Law equation. Regardless of addition and no addition of MgSO$_{4}$, the tendencies, that n value was decreased and K value was increased as aeration rate was increased, were shown. Simulated media of twelve different fermentation broths were formulated in a range of 0.7 to 2.1% CMC, and the values of gas hold-up and k$_{L}$a depending on superficial air velocity were measured using these simulated media. And the relation- ships, $\varepsilon$=$\alpha$U$_{Gr}$$\beta$, K$_{L}$a=$\gamma$U$_{Gr}$$\delta$ were obtained, and these equations are thought to be used to predict the values of gas hold-up and k$_{L}$a during fermentation.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.28-36
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• 2001

In this study, a zero-dimensional two zone model is developed to investigate the effects of valve overlap period and valve lift on combustion and gas exchange process in SI engine. The simulation results show that the predicted data has good agreements with experimental ones. The useful information of combustion and gas exchange process such as residual gas fraction, cylinder pressure, mass flow rate and volumetric efficiency can be obtained and the effects of engine variables on combustion processes and performances can be evaluated.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.252-258
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• 1999

As an effective means to convey crushed materials from seabed to on board ship and to raise hazardous or abrasive liquids air-lift pump provides a reliable mechanism due to its simple config-uration and easy-to-operate principle. The present study is focused on fundamental investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newto-nian liquids. it is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates and furthermore attachment of downcomer gives little effects on riser performance the conveyed liquid flow rate increases with larger submergence rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.82-88
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• 2001

The EGR is needed fur one of various strategies to reduce NOx emission. But to get the proper EGR rate, the intake and exhaust system become complicated. That is a reason why we consider using the internal EGR system. The internal EGR is a system which reduces NOx by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper, characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results, residual gas fraction and volumetric efficiency in cylinder by variable valve timing were visualized.