• 한국자동차공학회논문집
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• 제22권4호
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• pp.55-64
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• 2014

This work was investigated on pilot injection strategy of blended fuels(Diesel-DME) for combustion and emissions in a single cylinder direct injection compression ignition engine. Diesel and DME were blended by the method of weight ratio. Weight ratios for diesel and DME were 95:05 and 90:10 respectively. dSOI between main and pilot injection timing was varied. A total amount of injected fuels(single injection) was adjusted to obtain the fixed BMEP as 4.2 bar in order to compare with the fuel conditions. Also, the amount of pilot injection fuel was varied by 5%, 10% and 20% of total injection fuel. The engine was equipped with common rail and injection pressure is 700 bar at 1200 rpm. As a result, when mixing ratio increase, indicated thermal efficiency was increased in comparison with DD 100 and CO, THC and smoke were lower than DD 100. The influence of reducing NOx by pilot injection was more effective than DD 100. When pilot injection quantity increase, abrupt increase of NOx was occured at pilot injection quantity of 20%.

• 한국자동차공학회논문집
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• 제20권3호
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• pp.141-147
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• 2012

A direct injection diesel engine with large amount of exhaust gas recirculation was used to investigate low temperature diesel combustion. Pilot injection strategy was adopted in low temperature diesel combustion to reduce high carbon monoxide and hydrocarbon emissions. Combustion characteristics and exhaust emissions of low temperature diesel combustion under different pilot injection timings, pilot injection quantities and injection pressures were analyzed. Retarding pilot injection timing, increasing pilot injection quantity and higher injection pressure advanced main combustion timing and increased peak heat release rate of main combustion. As a result of these strategies, carbon monoxide and hydrocarbon emissions were reduced. Soot emission was slightly increased with retarded pilot injection timing while the effect of pilot injection on nitrogen oxides emission was negligible under low combustion temperature condition. Spatial distribution of fuel from the spray targeting visualization was also investigated to provide more insight into the reason for the reduction in carbon monoxide and hydrocarbon emissions.

• 한국자동차공학회논문집
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• 제18권4호
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• pp.132-139
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• 2010

This paper describes an investigation of the performance and emission characteristics of a commercial cylinder direct injection diesel engine operating on natural gas with pilot diesel ignition. Engine tests for variations in the pilot injection timing were performed at an engine speed of 1500 rpm. This study showed that the performance of the dual-fuel diesel engine increased as the engine load increased and as the pilot diesel injection timing angle advanced. The peaks of cylinder pressure, pressure rise rate, and heat release rate all increased while the fuel ignition timing advanced with the pilot injection timing. The engine operation was stable, and the least smoke was produced at a pilot injection timing of $12^{\circ}$ before top dead center. NOx emissions were only exhausted under high-load conditions, and they increased as the pilot injection timing angle advanced.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3007-3012
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• 2008

Multidimensional simulation has been carried out to be clear the role of initial combustion in a marine diesel engines on reduction of NOx and soot emissions by different pilot injection condition. Pilot injection can shorten the ignition delay, thus it reduces the premixed combustion phase. Since most NOx is formed during premixed combustion, pilot injections is one of reliable strategies to reduce the NOx. The formation of NOx consists of that formed by pilot injection and that formed by main injection. The result explains that 25-3-75 among the pilot injection conditions is effective to reduce the NOx, due to optimal combination pilot injection with main injection. The purpose of this study is to explain the characteristics of combustion with pilot injection of the marine diesel engine on reduction of exhaust emissions by examining the combustion process in a cylinder and to explore the formation mechanism of NOx between pilot injection and main injection.

• 한국산학기술학회논문지
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• 제15권5호
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• pp.2573-2578
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• 2014

본 연구는 4실린더 커먼레일 디젤 기관에서 바이오 디젤 혼합 연료를 사용하여 예비 분사시기와 EGR율을 변화시켰을 때 연소 압력과 배기 특성에 미치는 영향을 조사하기 위하여 실험을 수행하였다. 예비 분사 시기와 EGR율은 디젤 기관의 연소 및 배기 배출 특성에 큰 영향을 미친다. 본 연구에서는 일반적으로 많이 사용되고 있는 기관 회전 속도 2,000rpm에서 바이오 디젤 혼합율 20%의 연료를 사용하여 예비 분사 시기와 EGR율에 다양하게 변화를 주어 실험을 하였다. 실험결과, 도시 평균 유효 압력은 예비 분사 시기가 상사점전 BTDC $10^{\circ}$에서 가장 높았으며, 연소 압력과 열 발생율은 동일 예비 분사 시기에서 EGR율에 비례하여 감소하였다. NOx배 출량은 예비 분사시기에 관계없이 EGR율이 증가할수록 큰 폭으로 감소하였으며, 매연(Soot)은 예비 분사 시기 BTDC $20^{\circ}$에서 가장 적게 배출되었다.

• 한국분무공학회지
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• 제21권2호
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• pp.95-103
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• 2016

The effect of pilot injection quantity on the combustion and emissions characteristics of a compression ignition engine with a biodiesel-compressed natural gas (CNG) dual fuel combustion (DFC) system is studied in this work. Biodiesel is used as a pilot injection fuel to ignite the main fuel, CNG of DFC. The pilot injection quantity is controlled to investigate the characteristics of combustion and exhaust emissions in a single cylinder diesel engine. The injection pressure and injection timing of pilot fuel are maintained at approximately 120 MPa and BTDC 17 crank angle, respectively. Results show that the indicated mean effective pressure (IMEP) of biodiesel-CNG DFC mode is similar to that of diesel-CNG DFC mode at all load conditions. Combustion stability of biodiesel-CNG DFC mode decreased with increase of engine load, but no notable trend of cycle-to-cycle variations with increase of pilot injection quantity is discovered. The combustion of biodiesel-CNG begins at a retarded crank angle compared to that of diesel-CNG at low load, but it is advanced at high loads. Smoke and NOx of biodiesel-CNG are simultaneously increased with the increase of pilot fuel quantity. Compared to the diesel-CNG DFC, however, smoke and NOx emissions are slightly reduced over all operating conditions. Biodiesel-CNG DFC yields higher $CO_2$ emissions compared to diesel-CNG DFC over all engine conditions. CO and HC emissions for biodiesel-CNG DFC is decreased with the increase of pilot injection quantity.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.27-32
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• 2003

Diesel-Fueled HCCI(Homogeneous Charge Compression Ignition) Engine is an advanced combustion process explained as a premixed charge of diesel fuel and air is admitted into the cylinder and compression ignited. It has possibility to reduce NOx by spontaneous auto-ignition at multiple points that allows very lean combustion resulting in low combustion temperatures. Also PM could be reduced by the premixed combustion and no fuel-rich zones. But HCCI couldn't be realized because of the difficulties in vaporizing the diesel, control of combustion phase directly. To solve these problems, new fuel injection strategy, explained as the pilot fuel injection to promote ignition near TDC following the main fuel injection at the extremely advanced timing, is applied during the compression ratio is varied from 18.9:1 to 27.7:1 This is not a pilot fuel to promote the ignition but also the direct control method of the combustion phase. Experimental result shows the pilot fuel injection promote the ignition and the compression ignition of the HCCI engine is achieved as compression ratio becomes higher. Also there is an optimal pilot fuel injection timing for the HCCI combustion. NOx is reduced more than 90% compared to DI-Diesel case but PM and THC emission needs more investigation.

• 한국자동차공학회논문집
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• 제15권4호
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• pp.76-82
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• 2007

This paper described the effect of the multiple injections on the stability of combustion and emission characteristics in a direct injection diesel engine at various operating conditions. In order to investigate the influence of multiple injections in a diesel engine, the fuel injection timing was varied one main injection and two pilot injections at various conditions. The experimental apparatus consisted of DI diesel engine with four cylinders, EC dynamometer, multi-stage injection control system, and exhaust emissions analyzer. The combustion and emission characteristics were analyzed for the main, pilot-main injection, pilot-pilot-main injection strategies. It is revealed that the combustion pressure was smoothly near the top dead center and the coefficient of variations is reduced due to the effect of pilot injection. Also, $NO_x$ emissions are dramatically decreased with pilot injection because the decrease of rate of heat release. However, the soot is increased at early pilot injection and main injection.

• 한국분무공학회지
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• 제17권1호
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• pp.1-8
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• 2012

This study described the effect of the multiple injections and diesel-ethanol on the NVH, combustion and emission characteristics of 4 cylinder common rail diesel engine. In order to investigate the influence of diesel-ethanol blended fuel in a light-duty common rail diesel engine, the injection strategy was varied with pilot injection, double pilot injections, and one main injection at various operating conditions. The results showed that diesel-ethanol blended fuel had longer ignition delay than that of the ultra low diesel fuel(ULSD). Also, in the case of multiple injections, the combustion pressure is increased smoothly near the TDC and the NVH are decreased. In the emission characteristics, diesel-ethanol blended fuel produced lower indicated specific nitrogen oxides(IS-NOX) and indicated specific Soot(IS-soot) emissions, however, indicated specific unburned hydrocarbon(IS-HC) and indicated specific carbon monoxide(IS-CO) emissions are slightly increased.

• Journal of Advanced Marine Engineering and Technology
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• 제27권5호
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• pp.657-665
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• 2003

Combined De-NOx Process in which $NH_3$ SCR (Selective Catalytic Reduction) and non-thermal Plasma Process are simultaneously used, has been investigated with a pilot test facility. The pilot test facility treats the combustion flue gases exhausted from a diesel engine that generates 240 kW of electrical power. Test results show that up to 80 % of NOx (NO and NO2) can be removed at 100 - $200^{\circ}C$. None of conventional De-NOx techniques works under such low temperature range. In addition to NOx. the Pilot test results show that soot can be simultaneously treated with the present non-thermal plasma technique. The present pilot test shows that the electrical power consumption to operate the non-thermal plasma reactor is equivalent to 3 - 4 % of the electrical power generated by the diesel engine.