• 한국자동차공학회논문집
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• 제14권3호
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• pp.1-9
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Because this concept reduced NOx and smoke emissions simultaneously. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and intake air temperature affect the mixture formation. The purpose of this study is to investigate characteristics of combustion and mixture formation according to injection timing and intake air temperature in a common rail direct injection type HCCI engine using an early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel injection timing and intake air temperature affect the mixture formation and in turn affects combustion in the PCCI engine.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.66-72
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• 2002

A premixed charge compression ignition engine is experimentally investigated for the reduction of NOx and smoke emissions from diesel engines. In this study, the premixed fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber and then this pre-mixture is ignited by small amount of diesel fuel directly injected into the cylinder. In the premixed charge compression ignition engine, NOx and smoke concentrations of the exhaust emissions were reduced simultaneously as compared with the conventional diesel engine. But HC emission was increased with the increase of premixed ratio. Also, when EGR system was applied to the PCCI diesel engine, the effect of EGR rate on the combustion characteristics and the exhaust gas emissions was discussed.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.20-25
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and injection angle affects the mixture formations. Thus the purpose of this study was to investigate relationship of combustion and mixture formations according to injection timing and injection angle in a common rail direct injection type HCCI engine using a early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel. injection timing and injection angle affect the mixture formations and in turn affects combustion in the PCCI engine.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.101-104
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• 2012

In this work, in-cylinder pressure measurements and high-speed direct imaging of the flame were performed in an optically accessible single cylinder diesel engine with premixed charge compression ignition combustion and a narrow injection angle. The results show that the frequency ranges of pressure ringing were 8.35 to 9 kHz and 12..2 to 13.1 kHz. The frequencies of the flame movement were shown as 8.7 kHz and 13 kHz. It was found that there is a direct relationship between the pressure ringing and the flame movement.

• International Journal of Automotive Technology
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• 제8권5호
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• pp.543-553
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• 2007

It is becoming increasingly difficult for engines using conventional fuels and combustion techniques to meet stringent emission norms. The homogeneous charge compression ignition(HCCI) concept is being evaluated on account of its potential to control both smoke and NOx emissions. However, HCCI engines face problems of combustion control. In this work, a single cylinder water-cooled diesel engine was operated in the HCCI mode. Diesel was injected during the suction stroke($0^{\circ}$ to $20^{\circ}$ degrees aTDC) using a special injection system in order to prepare a nearly homogeneous charge. The engine was able to develop a BMEP(brake mean effective pressure) in the range of 2.15 to 4.32 bar. Extremely low levels of NOx emissions were observed. Though the engine operation was steady, poor brake thermal efficiency(30% lower) and high HC, CO and smoke were problems. The heat release showed two distinct portions: cool flame followed by the main heat release. The low heat release rates were found to result in poor brake thermal efficiency at light loads. At high brake power outputs, improper combustion phasing was the problem. Fuel deposited on the walls was responsible for increased HC and smoke emissions. On the whole, proper combustion phasing and a need for a well- matched injection system were identified as the important needs.

• 한국산학기술학회논문지
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• 제22권6호
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• pp.75-82
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• 2021

디젤엔진의 열효율을 높이면서 NOx와 PM을 효과적으로 저감시키기 위해 HCCI(Homogeneous Charge Compression Ignition), PCCI(Premixed Charge Compression Ignition), RCCI(Reactivity Controlled Compression Ignition) 등의 저온연소(LTC: Low Temperature Combustion)전략이 개발되어 왔다. 본 연구에서는 저반응성 연료로는 가솔린을 사용하고 고반응성 연료로는 디젤을 사용하는 RCCI 엔진에서 고반응성 연료인 디젤연료의 분사 시기와 이단 분사비율이 성능 및 배출가스에 미치는 영향을 수치해석을 통하여 파악하고자 하였다. 이단 분사 시 첫 번째 분사시기가 너무 진각되면 연소가 느려지면서 연소온도가 낮아져 연소성능이 저하되고 HC, CO가 증가한다. 대략 -60°ATDC 의 분사시기가 연소성능, 배출가스 및 최대압력상승률을 고려하였을 때 가장 최적의 분사시기라고 판단된다. 이단 분사 시 두 번째 분사시기를 변경하였을 때 연소성능 및 배출가스, 최대압력상승률 등을 고려하면 대략 -30°ATDC 부근에서 최적인 것으로 판단된다. 이단 분사 시 분사량 비율은 첫 번째 분사량을 60% 정도로 하였을 때 최적의 결과를 얻었다. 마지막으로 단일 분사보다는 이단 분사한 경우 연소성능 및 배출가스 부분에서 더 효과적인 것으로 판단된다.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.49-54
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• 2003

The purpose of this work is to investigate the effect of premixed fuel on the reduction of exhaust emissions in premixed charge compression ignition engine. The premixed fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber. The pre-mixture is ignited by a small amount of diesel fuel directly injected into the cylinder. In the case of gasoline as a premixed fuel of the engine, $NO_x$ and smoke concentration of exhaust emissions were reduced compared with the conventional diesel engine. But in the event of diesel fuel for premixed fuel, the rate of smoke reduction was small compared with the case of gasoline as a premixed fuel. HC and CO emissions were increased at high premixed ratio in the case of two premixed fuels. The combustion characteristics of the engine such as the combustion pressure, the rate of heat release, and other characteristics are compared.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.83-89
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• 2011

Diesel engines can produce higher fuel efficiency and lower $CO_2$ emission, they are subject to ever more stringent emission regulation. However, there are two major emission concerns fo diesel engines like such as particulate matter (PM) and nitrogen oxides (NOx). Moreover, it is not easy to satisfy the regulations on the emission of NOx and PM, which are getting more strengthened. One of the solutions is to apply the new combustion concept using multistage injection such as HCCI and PCCI. The other solution is to apply after-treatment systems. For example, lean NOx trap catalyst, Urea-SCR and others have various advantages and disadvantages Especially, Urea-SCR system have advantages such as a high conversion efficiency and a wide operation conditions. Hence the key factor to implementation of Urea-SCR technology, good mixing of urea(Ammonia) and gas, reducing Ammonia slip. Urea mixer components are required to facilitate evaporation and mixing because the liquid state of urea poses significant barriers for evaporation, and the distance to mixer is the most critical that affect mixer performance. In this study, to find out the distance from injector to mixer and simulation factor, a laser diagnostics and high speed camera are used to analyze urea injector spray characteristics and to present a distribution of urea solution in transparent manifold In addition, Droplet Uniformity Index is calculated from the acquired images by using image processing method to clarify the distribution of spray.