EFFECT OF FUEL INJECTION STRATEGIES ON THE COMBUSTION PROCESS IN A PFI BOOSTED SI ENGINE

S. S. MEROLA,P. SEMENTA,C. TORNATORE,B. M. VAGLIECO 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.5

A low-cost solution based on fuel injection strategies was investigated to optimize the combustion process in a boosted port fuel injection spark ignition (PFI SI) engine. The goal was to reduce the fuel consumption and pollutant emissions while maintaining performance. The effect of fuel injection was analyzed for the closed and open valve conditions, and the multiple injection strategies (MIS) based on double and triple fuel injection in the open-valve condition. The tests were performed on an optical accessible single-cylinder PFI SI engine equipped with an external boost device. The engine was operated at full load and with a stoichiometric ratio equivalent to that of commercial gasolines. Optical techniques based on 2D-digital imaging were used to follow the flame propagation from the flame kernel to late combustion phase. In particular, the diffusion-controlled flames near the valves and cylinder walls, due to fuel deposition, were studied. In these conditions, the presence of soot was measured by two-color pyrometry, and correlated with engine parameters and exhaust emissions measured by conventional methods. The open valve fuel injection strategies demonstrated better combustion process efficiency than the closed ones. They provided very low soot levels in the combustion chamber and engine exhaust, and a reduction in specific fuel consumption. The multiple injection strategies proved to be the best solution in terms of performance, soot concentration, and fuel consumption. A low-cost solution based on fuel injection strategies was investigated to optimize the combustion process in a boosted port fuel injection spark ignition (PFI SI) engine. The goal was to reduce the fuel consumption and pollutant emissions while maintaining performance. The effect of fuel injection was analyzed for the closed and open valve conditions, and the multiple injection strategies (MIS) based on double and triple fuel injection in the open-valve condition. The tests were performed on an optical accessible single-cylinder PFI SI engine equipped with an external boost device. The engine was operated at full load and with a stoichiometric ratio equivalent to that of commercial gasolines. Optical techniques based on 2D-digital imaging were used to follow the flame propagation from the flame kernel to late combustion phase. In particular, the diffusion-controlled flames near the valves and cylinder walls, due to fuel deposition, were studied. In these conditions, the presence of soot was measured by two-color pyrometry, and correlated with engine parameters and exhaust emissions measured by conventional methods. The open valve fuel injection strategies demonstrated better combustion process efficiency than the closed ones. They provided very low soot levels in the combustion chamber and engine exhaust, and a reduction in specific fuel consumption. The multiple injection strategies proved to be the best solution in terms of performance, soot concentration, and fuel consumption.

SI엔진의 냉간초기 HC 저감을 위한 포집백 및 컨트롤러 개발

김종일,차정연,손정배 조선대학교 환경연구소 2001 環境硏究 Vol.17 No.1

It is well known that unburned hydrocarbons are abundantly emitted into the atmosphere ate cold start in SI engine. Many nations tend to enforce regulations of emission much more strictly. This study was conducted to develop a system which reduces HC emissions at cold start using the device of temporary storage and recombustion after analyzing the emission characteristics of hydrocarbons during the cold start. The exhaust gas measurements are focused upon the first 30 seconds of operation after starting, with the engine and coolant initially at ambient temperature because this period has a major effect on HC emissions, over the FTP cycle. The engine examined is a 4-cylinder, 16-valve SI engine. K type thermocouples attached on the O_2 sensor, the catalytic converter and the coolant, and each sensor for the engine sere connected to the A/D board to find the parameters for storage time and reconbustion mode. The emissions were initially enriched in light fuel alkanes and depleted in heavy aromatic species. It was decided that the maximum storage time was 30 seconds at cold start. The time for storage was decreased with warmed start because the O_2 sensor's conversion at warmed start is much faster than that at cold start. The recombustion mode was selected by using the rate of throttle valve, engine speed, and operation conditions of purge solenoid valve to avoid engine torque fluctuation.

Performance and emission characteristics of a low heat rejection spark ignited engine fuelled with E20

C. Ramesh Kumar,G. Nagarajan 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.4

In internal combustion engines, the concept of low heat rejection (LHR) using thermal barrier coating on the surface of combustion chamber is gaining attention. Thermal barrier coating reduces the heat transfer to the cooling system, protects engine components from peak heat flux and fluctuating temperature produced during combustion and improves the performance of the engine. Information in the literature is plentiful for LHR diesel engine and only few studies exist on LHR spark ignited engine. The application of thermal barrier coating in spark ignited engine is limited by pre-ignition and knocking due to elevated combustion chamber temperature. A spark ignited engine with moderate insulation on the combustion chamber and higher octane fuel can overcome this difficulty. The objective of the present experimental study is to quantify the changes in performance and emission characteristics brought by partial thermal insulation on the combustion chamber of a four stroke spark ignited engine fueled with E20 blend. Partial thermal insulation was created by coating 0.3 mm thick Alumina (Al2O3) on the cylinder head, inlet and exhaust valves. The changes are quantified with respect to unmodified engine fueled with gasoline. The combustion parameters such as flame development and rapid burn duration are also estimated and compared. The results indicate that partially insulated SI engine when fueled with E20 improves performance and reduces emission. A maximum of 48% reduction in THC and 50% reduction in CO emission at part load was achieved.

INVESTIGATION OF RUNNING BEHAVIORS OF AN LPG SI ENGINE WITH OXYGEN-ENRICHED AIR DURING START/WARM-UP AND HOT IDLING

Xiao, G.,Qiao, X.,Li, G.,Huang, Z.,Li, L. The Korean Society of Automotive Engineers 2007 International journal of automotive technology Vol.8 No.4

This paper experimentally investigates the effects of oxygen-enriched air (OEA) on the running behaviors of an LPG SI engine during both start/warm-up (SW) and hot idling (HI) stages. The experiments were performed on an air-cooled, single-cylinder, 4-stroke, LPG SI engine with an electronic fuel injection system and an electrically-heated oxygen sensor. OEA containing 23% and 25% oxygen (by volume) was supplied for the experiments. The throttle position was fixed at that of idle condition. A fueling strategy was used as following: the fuel injection pulse width (FIPW) in the first cycle of injection was set 5.05 ms, and 2.6 ms in the subsequent cycles till the achieving of closed-loop control. In closed-loop mode, the FIPW was adjusted by the ECU in terms of the oxygen sensor feedback. Instantaneous engine speed, cylinder pressure, engine-out time-resolved HC, CO and NOx emissions and excess air coefficient (EAC) were measured and compared to the intake air baseline (ambient air, 21% oxygen). The results show that during SW stage, with the increase in the oxygen concentration in the intake air, the EAC of the mixture is much closer to the stoichiometric one and more oxygen is made available for oxidation, which results in evidently-improved combustion. The ignition in the first firing cycle starts earlier and peak pressure and maximum heat release rate both notably increase. The maximum engine speed is elevated and HC and CO emissions are reduced considerably. The percent reductions in HC emissions are about 48% and 68% in CO emissions about 52% and 78%; with 23% and 25% OEA, respectively, compared to ambient air. During HI stage, with OEA, the fuel amount per cycle increases due to closed-loop control, the engine speed rises, and speed stability is improved. The HC emissions notably decrease: about 60% and 80% with 23% and 25% OEA, respectively, compared to ambient air. The CO emissions remain at the same low level as with ambient air. During both SW and HI stages, intake air oxygen enrichment causes the delay of spark timing and the increased NOx emissions.

SI 희박연소 엔진의 연소특성에 미치는 EGR의 영향에 관한 실험적 연구

김치원(C. KIM),서병준(B. SEO),채태희(T. CHAE),오민석(M. OH),김대훈(D. KIM),이종진(J. LEE),이병호(B. LEE) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

As an intake process in the conventional spark ignition gasoline engine, the mixture with gasoline and air are inlet through the suction valve into cylinder, compressed and then ignited by an electric discharge, therefore the state of mixture is very important in the characteristics of combustion and emission. Therefore the lean operation is known to decrease the exhaust emission while maintaining a good fuel economy, but at very lean mixtures, the combustion rate has been resulted to reduce. In this experimental study, it is experimented and analyzed the combustion and emission formation according to intake some charge conditions in the lean bum and normal gasoline engine, which is modified the intake system with engine speed, EGR rates and gas temperatures. The following conclusions were drawn out by using the analysis of combustion and emission in this engine with engine speed, flow rates and temperatures of EGR. It is found that the maximum combustion pressure has risen in the condition of lower temperature more than higher temperature of the inflow exhaust gas. And the occurance crank angle of peak pressure has been advanced to the TDC. The brake specific fuel consumption in the cooled EGR gas has enhanced by 7 g/ps-h than that in the hot exhaust recirculation gas of engine charge. It has been verified that NO formation has been reduced as the flow rate of the cooled exhaust recirculation gas, but not reduced clearly the temperature of the hot EGR gas. The formation of unburned hydrocarbon has been reduced more in the case of 10% rate of EGR gas, and then found this phenomenon at lean mixture operation of this gasoline engine.

전기점화 기관의 시동 및 재시동 성능 연구

김성수 신라대학교 자연과학연구소 2002 自然科學論文集 Vol.10 No.-

Engine-out HCs emission were investigated during cold and hot start. The test was conducted according to engine cooling temperatures which were controlled by simulated coolant temperatures of cold and hot start, on a 1.5L, 4-cylinder, 16va1ve, multipoint-port-fuel-injection gasoline engine. Real time engine-out HCs emission were measured at exhaust ports and cylinder head using Fast Response Flame ionization Detector (FRHD). Unburned hydrocarbons emitted at the cold coolant temperature were much higher than that of the hot coolant temperature. And the main source of the high HC emission was confirmed as misfire at cold coolant temperature. In addition, the effect of intake valve timing on engine-out HC emission was investigated. The results obtained indicate that optimized intake phasing provides the potential for start-up engine-out HC emission reduction.

Carbon Coated Si-Metal Silicide Composite Anode Materials Prepared by High-Energy Milling and Carburization for Li-Ion Rechargeable Batteries

Choi, Woo Jeong,Reddyprakash, M.,Loka, Chadrasekhar,Jo, Young Woong,Lee, Kee-Sun The Electrochemical Society 2019 Journal of the Electrochemical Society Vol.166 No.3

<P>In this article, we report a novel Si-Metal silicides/Carbon composite anode material for lithium-ion rechargeable batteries. The composite powder comprised of Si, FeSi<SUB>2</SUB> and CrSi<SUB>2</SUB> were synthesized by high-energy mechanical milling and then a primary carbon was formed over the Si-silicide at 900°C. The prepared composite powder was agglomerated and subsequently a thin carbon layer was coated. The X-ray diffraction results revealed that the Si and silicide crystal size decrease with respect to milling time. The critical milling time to achieve the completely nano-scale powders was 5 h. The composite powder exhibits randomly distributed carbon-coated Si-silicide. The TEM microstructure revealed homogeneous distribution of nanocomposite powder consists a very fine nanoparticles of the order of ∼30 nm. The prepared Si-silicide/C composite powders exhibited good capacity retention with an average coulombic efficiency of 99.6%. The composite powders showed good cyclability, 1076 mAh g<SUP>−1</SUP> at 50<SUP>th</SUP> cycle and 959 mAh g<SUP>−1</SUP> at 100<SUP>th</SUP> cycle. The electrode internal microstructure revealed a shell-like carbon-coated Si-silicide phases, and a complete amorphization of nanocrystalline Si during the initial cycling, while the inactive silicide phase remains unchanged. Consequently, the size reduction of Si-silicide and carbon coating over it greatly enhanced the cycling performance of the electrode.</P>

Improved Performance in Charge-Trap-Type Flash Memories with an Al2O3 Dielectric by Using Bandgap Engineering of Charge-Trapping Layers

서유정,안호명,김희동,김태근 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

A band-engineered configuration of the new polycrystalline Si / Al2O3 / Si3N4 / SiO2 /Si (SANOS) device structure with a non-uniform nitride composition is proposed for high-density flash memories. The dramatic improvement can be attributed to the charge trapping efficiency, the data retention and the cycling endurance performance. The SANOS device designed in this paper holds promise for applications to next-generation charge-trap memory devices. A band-engineered configuration of the new polycrystalline Si / Al2O3 / Si3N4 / SiO2 /Si (SANOS) device structure with a non-uniform nitride composition is proposed for high-density flash memories. The dramatic improvement can be attributed to the charge trapping efficiency, the data retention and the cycling endurance performance. The SANOS device designed in this paper holds promise for applications to next-generation charge-trap memory devices.

Alternative fuels for internal combustion engines

Bae, Choongsik,Kim, Jaeheun Elsevier 2017 Proceedings of the Combustion Institute Vol.36 No.3

<P><B>Abstract</B></P> <P>This review paper covers potential alternative fuels for automotive engine application for both spark ignition (SI) and compression ignition (CI) engines. It also includes applications of alternative fuels in advanced combustion research applications. The representative alternative fuels for SI engines include compressed natural gas (CNG), hydrogen (H<SUB>2</SUB>) liquefied petroleum gas (LPG), and alcohol fuels (methanol and ethanol); while for CI engines, they include biodiesel, di-methyl ether (DME), and jet propellent-8 (JP-8). Naphtha is introduced as an alternative fuel for advanced combustion in premixed charge compression ignition. The production, storage, and the supply chain of each alternative fuel are briefly summarized, and are followed by discussions on the main research motivations for such alternative fuels. Literature surveys are presented that investigate the relative advantages and disadvantages of these alternative fuels for application to engine combustion. The contents of engine combustion basically consist of the combustion process from spray development, air–fuel mixing characteristics, to the final combustion product formation process, which is analyzed for each alternative fuel. An overview is provided for alternative fuels together with summaries of engine combustion characteristics for each fuel, in addition to its current distribution status and future prospects.</P>

실린더 내 유동해석에 레이저 기반 유동 진단기술 적용을 위한 실험용 Four-valve SI 기관의 설계 및 제작기술 개발

유성출 한국기계기술학회 2018 한국기계기술학회지 Vol.20 No.3

An AVL research engine, type 520, is modified to adapt to the 3.5L four-valve SI engine. With these given engine configurations, a test rig is constructed which allows easy changing of the different pistons and engine heads with a motoring capacity up to 3500 rpm. Nearly complete optical access to the inside of the cylinder is obtained by installing a transparent quartz cylinder on an AVL single cylinder engine. To avoid lubrication and to minimize scratches in the quartz cylinder the piston rings are made of Rulon-LD. With this experimental engine, researches for the in-cylinder flow characteristics by changing the induction system have been carried out using the laser based flow diagnostic techniques. In accordance with the previous result, it is evident that larger sized particles would be required in order to observe the flow characteristics of interest. The flow visualization taken with microballoon particles shows significant improvement. This provide detailed information.