• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.598-603
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• 2005

Biogas produced from anaerobic digestion processes has about 60% of methane and about 40% of carbon dioxide. Raw biogas can be used in internal combustion engines either spark ignition or diesel engines. Since the gas has relatively low calorific values, engine power also is lower than rated power values. Modified engines or biogas-specific engines have been utilized in order to increase efficiency. Another option is gas cleansing for increasing its calorific values. A couple of European countries adopted this approach in using biogas for one of transportation fuels, such as $CO_2$ scrubbing with water or special solutions. This study reports the results of water scrubbing for reducing $CO_2$ concentration. In 2.5m-high PVC pipe accepting water, $CO_2$ reduction rates were investigated. When flow rate of $CO_2$ and air mixture was about 5 LPM, $CO_2$ concentration was decreased up to 70%. Higher calorific biogas through water scrubbing is expected to be applied to various commercial engines without costly modification.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1050-1056
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• 2010

디젤기관은 공기만을 흡입 압축한 후에 연료를 분사하여 연소하기 때문에 높은 압축비가 가능하다. 높은 압축비에 의한 고효율의 장점과 연료의 직접분사에 의한 매연미립자의 배출 및 질소산화물의 배출이 많은 단점을 갖고 있다. 이러한 문제점을 해결하기 위하여 많은 연구들이 진행되었으며 수소를 흡기중에 공급하는 기술도 연구되고 있다. 본 논문에서는 미량의 수소를 연소실에 공급하여 엔진성능에 미치는 영향을 평가하였다. 토크와 엔진속도를 100%, 75%, 50%, 25%, 0%와 700rpm, 1000rpm, 1500rpm, 2000rpm로 구분하여 실험하였다. 실험결과 질소산화물이 약간 증가하였지만 연료소비율, 스모크와 일산화탄소 배출은 감소하였다. 수소의 첨가는 저부하 영역에서는 효과가 거의 없었지만 고부하 영역에서 큰 효과가 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제26권5호
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• pp.554-564
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• 2002

A newly designed combustion chamber of diesel engine with a modified piston crown was prepared for the purpose of investigation for reduction of NO emission. It was intended to realize 2-stage combustion that is to keep fuel rich condition during early stage of combustion and fuel lean condition during next stage. The engine was tested on various conditions concerning exhaust gas emissions especially about NO emission and simultaneously fuel consumption rate. It was found that the engine with 2-stage combustion type piston emits significantly low NO at various speed and torque compared with conventional engines, but it raised points at issue in CO and smoke emissions with fuel consumption rate. The increasing of injection pressure on 2 stage combustion type diesel engine affects on CO and smoke emission considerably to reduce but slightly on NO to increase. The effect of 2-stage combustion was better at low speed than at high speed.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.592-597
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• 2005

Biogas is widely accepted as one of renewable energy. Raw biogas can be used in internal combustion engines either spark ignition or diesel engines. Since the gas has relatively low calorific values, engine power also is lower than rated power values. Modified engines or biogas-specific engines have been utilized in order to increase efficiency. Recently, gas engine/generators are provided for various purposes. They are mostly for LPG or natural gas. When biogas is fueled to the gas engines, de-rating is inevitable due to its lower calorific values. Meanwhile, massively produced commercial gas engines are more competitive in terms of initial investment for engines, compared to biogas-specific engines. Then, the characteristics of the commercial engine and power generation should be understood for better operation. A 5kW gas engine/generator(natural gas) was tested for determining an allowable maximum concentration of $CO_2$ in synthetic biogas, with respect to engine stating, power generation. Experimental results indicated that about 65% of methane concentration is required to start the gas engine. At this condition, the power generated was about 3 kW. It is about 60% of the nominal power, which is similar to the ratio of calorific values.

• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.1010-1018
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• 2004

This study presents the methodological aspects of combustion instability modeling and provides the numerical results of the model (sub-scale) combustion chamber, regarding geometrical dimensions and operating conditions, which are for determining the combustion stability boundaries using the model chamber. An approach to determine the stability limits and acoustic characteristics of injectors is described intensively. Procedures for extrapolation of the model operating parameters to the actual conditions are presented, which allow the hot-fire test data to be presented by parameters of the combustion chamber pressure and mixture (oxidizer/fuel) ratio, which are customary for designers. Tests with the model chamber, based on the suggested scaling method, are far more cost-effective than with the actual (full-scale) chamber and useful for injector screening at the initial stage of the combustor development in a viewpoint of combustion instabilities.

• 한국연소학회지
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• 제18권4호
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• pp.21-28
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• 2013

HCCI engines have mainly focused on achieving low temperature combustion in order to obtain higher efficiency and lower emission. One of practical difficulties in HCCI combustion is to control the start of combustion and subsequent combustion phasing. The choice of primary reference fuels in HCCI strategy is one of various promising solutions to make HCCI combustion ignition-controlled. The behavior of ignition delay to the frequency variation of sinusoidal velocity oscillation is computationally investigated under HCCI conditions of PRF75 using a reduced chemistry in a counterflow configuration. The second-stage ignition is more delayed as the higher frequency is imposed on nozzle velocity fluctuation whereas the first-stage ignition is not much influenced.

• 한국연소학회지
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• 제15권4호
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• pp.53-57
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• 2010

The purpose of the present work is to investigate the effect of gasoline-premixing on a combustion and emissions characteristics in a compression ignition engine. For studying combustion characteristics, a combustion pressure and rate of heat release (ROHR) were measured using a single-cylinder DI compression ignition engine with a common-rail injection system and premixed fuel injection system. In addition, exhaust emissions characteristics were studied using emission analyzers and smoke meter. The experimental results showed that the case of gasoline-premixing had longer ignition delay and lower combustion pressure compared to the cases of diesel direct injection. Furthermore, premixed gasoline-air mixture reduced NOx emissions due to low peak of ROHR.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.363-366
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• 2012

Detonative combustion is considered as a promising combustion mechanism for improving thermodynamic efficiency of power generation systems as a PGC, as well as high-speed propulsion systems. Among the various types of detonative combustion, RDE is fascinated by many researchers because of the simplicity and continuos operation characteristics. Present paper is an introduction to the physical and operational concept of RDE with a brief history of RDE researches and recent development activities. Additional discussions will devoted to the relevance to the tangential mode instabilities in liquid rocket engines and improvement of liquid rocket performance.

• 한국분무공학회지
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• 제22권3호
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• pp.116-121
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• 2017

Pre-combustion chamber type indirect diesel engines have different combustion characteristics compared with those of common rail direct injection engine. The CONVERGE, specific engine CFD program, was used to simulate hollow cone spray model and combustion. The air-fuel mixture flow propagating from pre-combustion chamber to cylinder was concentrated at top half and center of the pre-combustion chamber throat. Stronger mixture flow was formed at smaller and longer throat cases. As a result, thermal efficiency and fuel consumption were improved for modified throat shape and the soot emission was also reduced.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.155-164
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• 1996

Dual-fuel engines are being researched with emphasis on the possible types of natural gas supply systems. Hence, a three-dimensional combustion model by using finite volume method was developed to provide a fundamental understanding of the auto-ignition of pilot distillate and subsequent burning of natural gas, when the natural gas as well as the distillate was directly injected into a quiescent diesel engine like combustion bomb tests and the numerical results were investigated for the mixed combustion phenomena. With high-pressure natural gas injection, it was found that the gaseous fuel injection characteristics had to be well harmonised with that of the pilot distillate. For better combustion efficiency, however, further researches are required for the optimisation of injection system in the existence of air motion.