• 동력기계공학회지
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• 제1권1호
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• pp.22-34
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• 1997

Circumstances require improving diesel engine, and many studies have been done in constant volume chamber(CVC). Because the combustion mechanism of a diesel engine has many difficulties with non-homogeneous nature, there has been a limitation to analyzing the combustion mechanism with CVC. Studies are often given in a real engine, but also it has difficulties in modifying configuration of combustion chamber etc. To get more easy way for mote engine-like test, a rapid compression mechanism has been introduced. This study addresses to designing a rapid compression expansion machine(RCEM) driven by compressed air, and to applying it on IDI diesel combustion chamber which has a glow plug. RCEM is introduced first and its characteristics are tested, then spray/combustion characteristics of diesel spray impinging on a glow plug in RCEM combustion chamber are investigated. The results show active combustion in the system employing spray impinging on a glow plug so as to improve combustion efficiency.

• 에너지공학
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• 제16권3호
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• pp.120-127
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• 2007

본 연구의 목적은 디젤연소장의 분위기조건에 따라 다성분 혼합연료의 질량분률이 분무착화 및 연소특성에 미치는 영향을 실험적으로 고찰하는데 있다. 착화 및 연소특성은 화학발광계측법 및 직접촬영법을 이용하여 분석되었다. 실험은 광계측기를 사용하여 RCEM에서 이루어졌으며, 이소옥탄, 노말 도데칸, 노말 헥사데칸으로 혼합한 다성분연료는 커먼레일 인젝터의 전자제어에 의해 RCEM의 연소실 내로 분사된다. 실험조건은 분사압력 42, 72, 112 MPa과 분위기온도 700, 800, 900 K로 하였다. 그 결과로서 착화지연은 고세탄가성분에 의존하고, 분위기온도가 낮을 경우 저비점성분 혼합비율의 증가에 따라 휘도영역이 현저하게 낮아지며, 열발생률이 증가하면서 확산연소기간을 단축시킨다.

• 연구논문집
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• 통권29호
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• pp.29-38
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• 1999

In comparison with gasoline engine, LPG direct injection engine has some advantages not only in emission and fuel efficiency but also in prevention of power decrease and back fire etc. which are disadvantages of conventional LPG engine. In this study, comparision tests of the incylinder spray and combustion characteristics between of LPG and gasoline fuels were performed in the RCEM as a basic research for the development of future LPG engine with low emission and high fuel efficiency During the direct injection of LPG fuel and gasoline into the inside of RCEM, spray development characteristics according to the injection condition have been photographed by the high speed shadow graph methods. The conditions for the optimum mixture distribution of LPG and gasoline fuels are achievable at the selected ignition timing, respectively.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.250-261
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• 1995

In this study, a rapid compression and expansion machine(RCEM) equipped with a swirl generator was designed and developed, in order to clarify normal and abnormal combustion(knocking phenomena). This RCEM is intended to simulate combustion process in actual automotive S.I.engines, having a high reproducibility in the compression stroke. Flame propagation and autoignition processes associated with normal and abnormal combustion were captured by the high speed schlieren photography. And swirl intensity. equivalence ratio and ignition position were varied to investigate the effect of turbulence, concentration in the unburnt gas region and flame propagation length. The knock intensity, knock mass fraction and knock mass fraction after autoignition were calculated by use of history of measured cylinder pressure.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.76-85
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• 1999

GDI(Gasoline Direct Injection( engine technology is well known as a new technology since it can improve fuel consumption and meet future emission regulations. But the GDI has many difficulties to be solved, such as complexity of injection control mode, unburned hydrocarbon, and restricted power. A 2-D shape combustion chamber was adopted to investigate mixture formation and combustion characteristics of GDI engine. Spray and combustion experiments were performed by changing the injection timing. injection pressure an din-cylinder flow in Rapid Compression and Expansion Machine(RCEM).Through the experiments, the detailed characteristics of fuel spray and combustion was analyzed by visualizing the in-cylinder phenomena according to the change of injection condition, and the optimal fuel injection timing and fuel injection pressure were obtained.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.103-110
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• 1998

This experiment is performed to investigate the effects of the emulsion on the flame temperature and soot formation in a diesel engine. The two-color method is used to measure the flame temperature for combustion of emulsified diesel in the Rapid Compression and Expansion Machine(RCEM). The concentration of soot is estimated via calculation of the KL factor. The solenoid valve, elecronic controller and needle lift sensor are used to control the exact injection timing and duration under various operating conditions. According to the results the soot concentration is reduced with the increasing W/O while the temperature reduced. The pressure data and the flame images captured by a high speed camera show that the ignition delay of emulsified diesel increase the duration of premixed combustion. The sizes of water drops are measured to be about 10${\mu}m$ by a microscope.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.487-492
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• 2010

For developing a two-stroke free-piston hydrogen engine with high efficiency and low emission, determination of the scavenging type is one of the most important factor. In this research, backfire characteristics for loop scavenging were analyzed with the number of piston crevice volume and piston expansion speed. Rapid Compression Expansion Machine, RCEM was used for combustion research of the free piston $H_2$ engine in the experiment. As the results, it was shown that although backfire occurring in a loop scavenging type can be partially controled by a complete exhaust of burned gas, possibility of backfire basically exist due to the structure which piston crevice volumes contact with fresh mixture in a scavenging port. However, a loop scavenging may be considered as combustion chamber of a free piston $H_2$ engine from the point of view that backfire does not occur nearby lean equivalence ratio obtained high thermal efficiency. It was also analyzed that an advances of backfire occurrence timing with increase of the fuel-air equivalence ratio were due to promotion of flame propagation into piston crevice volumes by decrease of the quenching distance.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.8-14
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• 2007

Compression ignition of homogeneous charges in IC engines indicates possibilities of achieving the high efficiency of DI diesel engines with low level of NOx and particulate emissions. The objectives of this study are to further understand the characteristics of the HCCI(Homogeneous charge compression ignition) combustion and to find ways of extending the rich HCCI operation limit in an engine-like environment. DME fuel is supplied either in the form of premixture with air or directly injected in the combustion chamber of a rapid compression and expansion machine under the conditions of various equivalence ratio and injection timing. The cylinder pressure is measured and the rate of heat release is computed from the measured pressure for the analysis of the combustion characteristics. The experimental data show that the RCEM can operate without knock on mixtures of higher equivalence ratio, when DME is directly injected in the combustion chamber than introduced as a fraction of a perfect or nearly perfect premixture. Very early fuel injection timings usually employed in HCCI operation are seen to have only insignificant effects in control of ignition timing.