• 대한기계학회논문집B
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• 제31권8호
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• pp.718-723
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• 2007

The new concept spark plug was developed to study its influence on the combustion characteristics of SI engine. It has pre-ignition chamber in the lower end of spark plug and flame hole, in which fresh mixture gas can be introduced without any fuel supply system. This spark plug was tested with a commercial SI engine. Fuel consumption rate, emission gas and MBT timing were measured in the engine dynamometer for various flame hole numbers, hole positions, hole sizes of the pre-ignition chamber of the spark plug. And average flame propagation speed was measured by using the head gasket ionization probe in single cylinder engine. The new concept spark plug induces fast bum in combustion compared with the conventional spark plug, and MBT(Minimum advance for Best Torque) timing was retarded about $3{\sim}5^{\circ}$ crank angle. The flame hole number, hole direction and volume of pre-ignition chamber were found to influence the combustion characteristics.

• International Journal of Automotive Technology
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• 제7권7호
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• pp.763-768
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• 2006

Emission reduction in the cold start period of SI engines is crucial to meet stringent emission regulations such as SULEV Emissoin reduction is the starting point of the study in the which the variable valve timing (VVT) technology may be one promising method to minimize cold start emissions while maintaining engine performance. This is because it is possible to change valve overlap and residual gas fraction during cold start and idle operations. Our previous study showed that spark timing is another important factor for reducing cold-start emissions since it affects warm-up time of close-coupled catalysts (CCC) by changing exhaust gas temperature. However, even though these factors may be favorable for reduction of emissions, they may deteriorate combustion stability in these operating conditions. This means that the two variables should be optimized for best exhaust emissions and engine stability. This study investigated the effects of valve and spark timings in idle performance such as combustion stability and exhaust emissions. Experiments showed that valve timings significantly affected engine stability and exhaust emissions, especially CO and $NO_x$, due to change in residual gas fraction within the combustion chamber. Spark timing also affects HC emissions and exhaust gas temperature. Yet it has no significant effects on combustion stability. A control strategy of proper valve timing and spark timing is suggested in order to achieve a reduction in exhaust emissions and a stable operation of the engine in a cold start and idle operation.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.295-301
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• 2006

A new combustion method of high compression ratio SI engine was studied and proposed in order to achieve high thermal efficiency, comparable to that of CI engine. Compression ratio of SI engine is generally restricted by the knocking phenomena. A combustion chamber profile and a cranking mechanism were studied to avoid knocking with high compression ratio. Because reducing the end-gas temperature will suppress knocking, a combustion chamber was considered to have a wide surface at the end-gas region. However, wide surface will lead to large heat loss, which may cancel the gain of higher compression ratio operation. Thereby, a special cranking mechanism was adapted which allowed the piston to move rapidly near TDC. Numerical simulations were performed to optimize the cranking mechanism for achieving high thermal efficiency. An elliptic gear system and a leaf-shape gear system were employed in numerical simulations. Livengood-Wu integral, which is widely used to judge knocking occurrence, was calculated to verify the effect for the new concept. As a result, this concept can be operated at compression ratio of fourteen using a regular gasoline. A new single cylinder engine with compression ratio of twelve and TGV(Tumble Generation Valve) to enhance the turbulence and combustion speed was designed and built for proving its performance. The test results verified the predictions. Thermal efficiency was improve over 10% with compression ratio of twelve compared to an original engine with compression ratio of ten when strong turbulence was generated using TGV, leading to a fast combustion speed and reduced heat loss.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• 한국대기환경학회지
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• 제13권4호
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• pp.307-317
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• 1997

Samples of fine particle $(d_P<2.5 \mum)$ were taken in Chongju area using a dichotomous sampler. The data set was collected on fifty-eight different days with 24 hour sampling period from October 27, 1995 through August 25, 1996. The samples were analyzed using a proton induced x-ray emission (PIXE) for Na, Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, M, Fe, Ni, Cu, Zn, Br and Pb. Values of Fe, Ca, Si, Cu, K and Cl exhibit marked seasonal variations. Mean concentrations for this study had the following order S > Cl > Si > K > Al > Fe on fine particle. Concentrations of Ca, Si and Fe were higher during the spring season compared with any other season. These phenomena may be attributable to soil dust. Cl and K were higher in the winter, which may be explained by combustion of fossil fuel. Higher values for Cu and Zn in the Winter may be due to the combustion and incineration.

• 대한기계학회논문집B
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• 제32권8호
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• pp.582-588
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• 2008

An experimental investigation was conducted to investigate the effect of Bio-ethanol fuel on the engine performance and exhaust emission characteristics under various engine operating conditions. To investigate the effect of bio-ethanol fuel, the commercial 1.6L SI engine equipped with 4 cylinder was tested on EC dynamometer. The engine performance including brake torque, brake specific fuel consumption, and barke specific energy consumption of bio-ethanol fuel was compared to those obtained by pure gasoline. Furthermore, the exhaust emissions were analyzed in terms of regulated exhaust emissions such as unburned hydrocarbon, oxides of nitrogen, and carbon monoxide.Result of this work shows that the effect of blending of ethanol to gasoline caused drastic decrease of emissions under various operating conditions. Also, improved engine performance such as brake torque and brake power were indicated for bio-ethanol fuel.

• 한국세라믹학회지
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• 제36권2호
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• pp.203-209
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• 1999

Si 기판위에 Ba2YCu3O7-$\delta$ 고온초전도체를 응용하기 위해 요구되는 buffer층으로 유망한 재료인 LaAlO3 단일상 분말을 고상반응법과 자발착한 연소반응법으로 제조하였다. 제조된 LaAlO3 분말의 입자형태와 결정상태는 scanning electron microscope (SEM)과 X-ray diffractometer (XRD)를 이용하여 분석하였다. 분말의 비표면적과 소결특성은 각각 Brunauer-Emmett-Teller(BET) 방법과 dilatometer를 측정하였다. 고상반응법으로 LaAlO3 분말을 제조할 때에는 하소온도를 150$0^{\circ}C$까지 높게 하여도 단일상을 얻는 것이 어려웠으나 자발착한 연소반응법에 의한 분말제조는 $650^{\circ}C$의 저온에서 하소하여도 쉽게 얻을 수 있었다. Dilatometer 측정을 통하여 분석해 보면, 고상반응법에 의한 분말보다 자발착한 연소반응법에 의한 분말로 제조된 소결체가 고상반응법에 의한 소결체에 비해 1.4배나 큰 소멸밀도(98.87%)를 가졌다. 이렇게 소결밀도에서 큰 차이가 나는 것은 자발착한 연소방법에 의한 분말의 평균 입자크기가 nano crystal size이고 비표면적 값(56.54 $m^2$/g)이 매우 크기 때문이다. 두가지 방법으로 제조된 분말을 이용, LaAlO3 layer를 스크린 프린팅과 소결법으로 Si 기판상에 제조하였으며 자발착한 연소합성법으로 제조된 분말은 110$0^{\circ}C$에서 우수한 소결특성을 나타내었다.

• Transactions on Electrical and Electronic Materials
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• 제15권5호
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• pp.249-252
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• 2014

The aim of this work is to investigate the effect of $Ca_xSr_{2-x}$ and activator on the structural and luminescent properties of green-emitting $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ nano phosphor. Using urea as fuel and ammonium nitrate as oxidizer, $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ has been successfully synthesized, using a combustion method. The particles were found to be small, spherical and of round surface. SEM imagery showed that the phosphors particles are of nanosize. The $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ emission spectrum for 360 nm excitation showed a single band, with a peak at 490 nm, which is a green emission. The highest luminous intensity was at $1,000^{\circ}C$, which was obtained when the $Eu^{2+}$ content (y) was 0.05. The results support the application of $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor as a fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). Characteristics of the synthesized $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) detection.

• 대한금속재료학회지
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• 제48권5호
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• pp.417-423
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• 2010

A dense nanostructured MoSi$_{2}$-SiC composite was synthesized by a pulsed current activated combustion synthesis method within 2 min of one step from mechanically activated powders of Mo$_{2}$C and Si. Simultaneous combustion synthesis and consolidation were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense MoSi$_{2}$-SiC with a relative density of up to 98% was produced under simultaneous application of an 80 MPa pressure and pulsed current. The average grain size and mechanical properties of the composite were investigated.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 춘계 학술발표강연 및 논문개요집
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• pp.118-118
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• 2002