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In this study, the impact of engine control parameters on combustion behaviors and particle number emissions was investigated with a spark ignition direct injection (SIDI) engine used various gasoline-ethanol blended fuels. The SIDI engine was tested with the E0, E30 and E85 at a engine operation of 1500 rpm/1.5 BMEP. The combustion pressure and mass burn fraction (MBF) according to the control parameters and ethanol fractions were analyzed. To verify the PN oxidation characteristics of the ethanol blended fuels, the size-resolved PN emissions over the three-way catalyst (TWC) were determined with a DMS500. The peak pressure in the cylinder was similar regardless of the type of fuel and the particle emissions were reduced by 92 % compared to gasoline at the engine out position in the E85 fuel. The results show that gasoline-ethanol blends have potential as alternative fuels and are effective in reducing the particle emissions in internal combustion engines.

Worldwide regulations on particulate matter for passenger vehicles have become stricter in recent years, which makes it difficult to satisfy for gasoline direct injection (GDI) vehicles. In this study, the level of reduction efficiency of particle emissions with a metal-foam gasoline particulate filter (GPF) for the turbocharged GDI vehicle was evaluated in the federal test procedure (FTP)-75 mode operation. The particle number (PN) emissions were analyzed using the AVL particle counter (APC) and fast response differential mobility spectrometer (DMS500) for particle size distribution. The PN concentration from the base GDI vehicle with only TWC is 1.64 E+12 number/km (#/km), while the value of the GPF-equipped case is 5.02 E+11 #/km with 69 % filtration efficiency in the vehicle test mode. In particular, the reduction rate of small particles under 23 nm in size was strongly improved with the additional installation of the metal-foam GPF. The maximum pressure drop through the GPF reached approximately 39 mbar at the highest acceleration point of phase 1 of the FTP-75 mode. The upstream temperature of the GPF was distributed at approximately 380 ∼ 510 oC in the vehicle test. The results show that the GPF-equipped GDI vehicle can satisfy the stringent particle regulation by Euro 6 in a straightforward manner.

This study investigated the impact of engine oil formulation on particulate matter (PM) characteristics from a light-duty diesel engine. The test engine was a 1.6 L Euro-5 diesel engine operated from low- to high-speed and high-load conditions. Specially formulated nonadditive containing base oil and genuine oil were evaluated. For diesel PM characterization, physicochemical analytic procedures were conducted on engine oil formulation, oil flushing, PMs sampling, morphology, and particle constituent determination. Size-resolved particle number (PN) concentration at the engine-out position was evaluated by differential mobility spectrometer (DMS). Nucleation mode particles originating from engine oil consumption during the expansion stroke had a higher concentration from genuine oil than those from base oil. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology patterns and atomic compositions with engine oil packages. From the SEM analysis, spherical PM of nucleation and accumulation mode particles were agglomerated on a quartz filter. In the XPS spectrum, more engine oil additive fractions of Ca, P, and Zn were found in the PM sample from genuine oil. In conclusion, the variation of physicochemical engine oil properties and additive amounts had strong contributions to engine oil derived PN emissions, morphology, and additive metal compositions in the exhaust gas stream.

Test flexibilities, such as the tire pressure, adjustment of brakes, vehicle preconditioning, test mass, and running-in period, are multiple factors that can confound vehicle emissions and fuel economy tests. The road load force is the most influential flexibility factor for a type-approval vehicle certification test. Because of these various factors, it was revealed that there was a substantial difference between the type-approval emissions and those from a real-driving emissions test. In this study, the test cycle road load energy using the road load coefficients determined by the TA coast-down procedure was the base condition. After calculating the test cycle road load power, the constant term of the road load coefficient was adjusted by the energy loss. The tolerance of the road load in domestic regulation is 15%, so the constant term of the road load coefficient was increased by 5% in the cycle road load energy loss. Then, the road load power and tractive power were calculated from the force and vehicle speed. The vehicle fuel efficiency, under the road load variation conditions, was determined for modern 2.4 L gasoline direct injection and lean NOxtrap-equipped diesel vehicles on a chassis dynamometer. To assess the impact of different road load values on the FE and carbon dioxide emissions, the test cycle was performed over the combined modes of the federal test procedure-75 and the highway fuel economy test. To investigate the road load variations of the vehicle fuel economy in correlation with the energy difference, the statistical approach of the one-way analysis of variance was applied. The results showed that the variations of the road load energy of the tested cycle were closely related in a trade-off relationship with the vehicle fuel economy.

Certified testing of motor vehicle driving resistance, fuel economy and emissions requires that the vehicle has reached the target distance specified for each country through running-in. In general, motor vehicles experience different tire wear and internal resistance profiles from their moving parts, including the brake, hub bearing, drive shaft and transmission, depending on how they have performed running-in over what range. This means that such differences can result in a discrepancy in the level of mechanical resistance that consists of tire rolling resistance and internal resistance. There is thus a potential impact on the fuel economy and emissions as tested by the chassis dynamometer. In this study, the nomenclatures define where the running-in testing takes place (“Location”), how the testing is performed (“Mode”) and over which distance the testing takes place (“Distance”) as the factors having the major impact on the mechanical resistance of a motor vehicle. Then the mechanical resistance was measured under different running-in distances using a chassis dynamometer and the determination was made on how the resistance decrease over the range to understand statistically how Location and Mode affect the reduction in mechanical resistance under different Distances. This study was also evaluated on which running-in test mode is the best for fuel economy and emissions certification through total cost analysis over the 6,500 km running-in distance. In addition, the process to identify the impact of vehicle running-in test conditions on the reduction in the mechanical resistance of the vehicle was suggested.

To meet greenhouse gas (GHG) emission target, automotive manufacturers should promote low carbon emission technology, including gasoline direct injection (GDI) systems. However, recent studies have shown that excessive levels of nanoparticles were emitted from GDI vehicles compared to port fuel injection (PFI) vehicles. One of the many ways to decrease nanoparticle emissions from GDI engine is to use alternative fuel This study used turbo charged 2.0 L 4-cylinder LPG direct injection engine (T-LPDi) that was converted from a turbo charged gasoline direct injection engine (T-GDI) with dedicated LPG fuel supply and control system. To analysis on combustion phenomena and nanoparticle emissions, in-cylinder pressure and exhaust gas were measured under engine dynamometer test. Additionally, various engine control parameters were swung to understand the effects of the control parameters on combustion and nanoparticle characteristics. Throughout this study, T-LPDi engine, compared to T-GDI engine, showed ∼ 9 % and 76 % reduction of CO2 and PN emissions respectively. By optimizing engine parameters based on parametric study, PN emissions were improved 70 % from the baseline of T-LPDi engine emissions.

As global warming and fine dust problem became issues, the regulation for relevant exhaust emissions has been strengthened gradually. Thus, a major challenge of automotive engineers is reducing the CO2 and particle emissions at the same time. Especially for gasoline direct injection (GDI) engines, which are widely used due to its higher fuel efficiency, an excessive particle emissions problem compared to port fuel injection system is the big nuisance. The LPG fuel, which has great fuel properties for applying this direct injection scheme, could deal with this. Also, downsized turbocharged system can reduce additional fuel consumption and CO2 emissions sequentially. In this study, a GDI passenger car and the same vehicle equipped with a downsized turbocharged liquefied petroleum gas direct injection (T-LPDi) engine were evaluated under chassis dynamometer test to verify the exhaust emission abatement capability of T-LPDi vehicle. The T-LPDi engine was developed for research use, which has dedicated fuel supply and control strategy for LPG fuel. Comparing the T-LPDi and GDI vehicles, the CO2 emissions were decreased by > 20% under the vehicle test condition, while particle number and mass emissions were decreased by > 90% and >50% from the T-LPDi vehicle respectively. These results showed a potential of T-LPDi concept as a good alternative with the environmental competitiveness, though there is room for further improvement of engine control and optimization of emission catalyst to meet more stringent future regulations.

This work investigated the aged diesel particulate filter substrate analysis procedure and ash physicochemical analysis method with various instruments such as CT, XPS, SEM and XRD. The procedure for analyzing two DPFs aged with the same lubricant oil but located in different locations was followed to determine the ash formation mechanism. We analyzed DPFs in their non-destructive state with X-ray computed tomography to determine the form how the ash was deposited, and after decanning the DPF, we verified ash formation with micro X-CT. A scanning electron microscope was used to determine the morphology of the ash and DPF substrates, and the distributions of the components were analyzed using energy dispersive spectroscopy. The ash pellets were used for X-ray photoelectron spectroscopy analysis to determine the percentages of different components, and the crystal structure of the ash powder was determined using a X-ray diffractometer. The result of this study is that the deposition patterns and composition of the ash components differ depending on where the DPF is mounted due to differences in temperature and pressure experienced during aging. Calcium is accounted for the largest percentage of the materials that formed the ash.

Particle number (PN) emissions must be below 9.0 × 1011 #/km according to the Euro 6d regulation with a conformity factor (CF) of 1.5 during a real driving emissions (RDE) test, including the cold start phase. Thus, the object of this study is to analyze the on-road PN emissions characteristics under a cold start condition of a gasoline direct injection (GDI) vehicle depending on a catalytic stripper (CS), a gasoline particulate filter (GPF), the cold start phase, and the trip section using a corona charger type particle sensor, a CS, and an exhaust flow meter. Because the fuel-rich mode and retarded injection timing were applied to compensate for engine instability and caused incomplete combustion and deterioration of fuel vaporization during the cold start phase, PN emissions during the cold start phase accounted for a significant portion of the total PN. On-road PN emissions for the total trip were 2.71 × 1012 (without CS and GPF), 1.72 × 1012 (with CS and without GPF), 1.47 × 1012 (without CS and with GPF) and 9.50 × 1011 (with CS and GPF) #/km for cases A, B, C and D, respectively. The average CS effects on the decrease of PN emissions were 35.4% and 32.2% in the urban, 52.2% and 63.4% in the rural, 22.8% and 88.6% in the motorway, and 36.5% and 35.6% in the total trip sections without and with GPF, respectively. The average GPF effects on the reduction of PN emissions were 42.7% and 39.9% in the urban, 58.2% and 68.0% in the rural, 27.9% and 89.3% in the motorway, and 45.6% and 44.8% in the total trip sections without and with CS, respectively.

Since it is common for vehicles with idle engines to be stored indoors during the winter season to remain warm, better constraints are needed for idling emissions at low ambient temperature. CH4 (methane), C2H6 (ethane), C2H4 (ethylene), HNCO (isocyanic acid), N2O (nitrous oxide), NH3 (ammonia), C3H6 (propylene), and HCHO (formaldehyde) from many unregulated exhaust emissions were selected and measured by a Fourier Transform Infrared Spectroscopy (FTIR) analyzer in this study. This paper investigates the idling regulated and unregulated emissions of Euro 5/6 diesel vehicles at cold start and hot restart near 0 °C conditions. The impact of cold start and hot restart on NOx idling emissions was lower than CO and HC idling emissions in diesel vehicles. With regard to unregulated emissions, high fuel–air equivalence ratios and longer ignition delay in the idle cold start condition may increase incomplete combustion and affect the thermal cranking processes, leading to the increase of CH4, C2H4 and C3H6. Furthermore, as the formation of N2O is considerably affected by the equivalence ratio and cylinder temperature, a high fuel-air equivalence ratio at low ambient temperature in the cold start condition resulted in the increase of N2O emissions.

Although the chassis dynamometer type approval test considers real-world conditions, there are a few limitations to the experimental test environment that may affect gaseous or particulate emissions such as road conditions, traffic, decreasing tire pressure, or fluctuating ambient temperature. Furthermore, the real driving emission (RDE) test takes a long time, and it is too long to repeat under different experimental conditions. The National Institute of Environmental Research (NIER) test modes that reflect the driving pattern of Korea are not certification test modes, but can be used to evaluate the influence of traffic conditions because these modes consist of a total of 15 test modes that vary according to average speed. The use of the NIER #03, #09, and #13 modes as low-, medium-, and high-speed modes allow for gaseous and particulate emissions to be measured and analyzed. Additionally, the worldwide harmonized light-duty vehicle test procedure (WLTP), the certification mode of Europe, is used to test cycles to investigate the difference under cold- and hot-engine start conditions. The engine operating parameters are also measured to evaluate the relationships between the various test conditions and test cycles. The regulated and greenhouse gas levels decrease under various driving conditions, but the particle number (PN) emission level shows a different trend with gaseous emissions. While the PN and CO2 results dramatically increase when the air conditioner is on, tire pressure conditions show different PN size distributions: a large-sized PN fraction, which contains particles larger than 100 nm, increases and a sub-23 nm-sized PN fraction decreases. Under cold-start conditions in the WLTP modes, there are much higher PN emissions than that of an engine under hot-start conditions, and the sub-23-nm-sized PN fraction also increases.

This study investigated the effects of various ethanol-gasoline blends on the hazardous air pollutants (HAPs) emissions from a wall-guided direct injection passenger vehicle. The fuel economy (FE) as well as regulated and unregulated gaseous emissions was evaluated on a chassis dynamometer using the federal test procedure (FTP-75) mode. Five fuels with varying ethanol contents of E0, E10, E30, E50, and E85 were prepared by blending ethanol into commercial gasoline on a volumetric basis and were analyzed each fuel specification. The engine control schemes of fuel injection quantity for various ethanol blends were adjusted to optimize the engine starting capability, vehicle drivability and emissions performance. The FE of the E85 fueled vehicle decreased by 29% relative to gasoline fuel due to the low energy content of ethanol. Blending ethanol into gasoline produced a dramatic decrease of particulate emission, because pure ethanol has no aromatic compounds and carbon content lower than that of gasoline. As a result, nano-particles were rarely emitted in the vehicle tests of fuels with more than 30% ethanol. Carbonyl compounds emissions, which originate from partial oxidization or incomplete combustion of ethanol, also rose sharply as the ethanol content increased, while volatile organic compound (VOC) emissions were reduced considerably with medium- and high-ethanol formulations due to the lower proportion of aromatic components in these fuels.

Construction of harmful emission inventory from conventional and sustainable low carbon fueled vehicles is important issues to improve urban air quality and human health. In this study, the gaseous, nanoparticle, and unregulated gaseous emission formation behavior from a medium-duty minibus were investigated using the World Harmonized Vehicle Cycle (WHVC). The state-of-the-art diesel and turbocharged direct-injection liquefied petroleum gas (LPG) vehicle were tested on a chassis dynamometer. The after-treatment system of the 3.9-L diesel engine was composed of the DOC, DPF and SCR, which satisfy the Euro 6 emission regulation. The 3.3-L stoichiometric spark ignition direct injection LPG engine was a TWC-only system. The formation of harmful emission components from the light-duty minibus operation was closely related to powertrain types, combustion mechanisms, after-treatment devices, and physicochemical properties of the tested fuels. Additionally, the chemical composition and low heating value (or energy content) of the respective fuels substantially affected the vehicle CO2 emissions and fuel economy performance. Compared to LPG vehicle, the THC and NOx emissions from diesel vehicle were 63% and 511%. Similar PN concentrations were measured with each powertrain, but 2–3 times higher nucleation mode particles were released with diesel vehicle. Two vehicles showed comparable CO2 emissions, while fuel economy from diesel and LPG vehicle were 6.81 km/L and 4.60 km/L. The proportions of N2O and CH4 emissions with ozone forming potential (OFP) were 1.2% (diesel) and 0.3% (LPG), which showed the potential to mitigate the CO2-equivalent emissions from LPG minibus.

Advanced nitrogen oxides (NOx) after-treatment systems for diesel cars are effectively reducing tailpipe NOx emissions in laboratory test cycles; however, some de-NOx systems showed limitation for passing environmental standards during real-world driving conditions. In this study, the NOx concentration of a lean NOx trap (LNT)-equipped diesel engine were investigated over various vehicle certification cycles. The LNT performance was compared to the new European driving cycle (NEDC), world-harmonized light-duty vehicle test cycle (WLTC), federal test procedure (FTP)-75, highway fuel economy test (HWFET), and US06. The real-time NOx concentration behaviors were tracked using NOx sensors at the engine-out and downstream of the LNT to determine the NOx storage and regeneration phase. The NOx conversion efficiencies were 36.3–71.7% of which reflecting the mode severity and cycle duration of the diesel engine. The tailpipe NOx emissions were 0.059 g/km during the NEDC which was within the Euro-6 emissions regulations. The NOx emissions in the WLTC, FTP-75, and US06 modes were approximately 1.9, 1.5, and 6.6 times higher than the NEDC due to the higher frequency of LNT purge and higher engine-out NOx formation. During the diesel particulate filter (DPF) regenerating stage in WLTC mode, tailpipe NOx emissions substantially increased by more than 8.8-fold. The exhaust gas recirculation (EGR) supply and lambda control scheme were closely related with strong NOx increment at de-NOx and de-PM processes.

Euro 6-compliant diesel passenger cars have tended to feature lean NO x traps (LNTs) to satisfy the increasingly stringent NO x regulations. This paper focused on NO x emission characteristics by the NO x sensors installed at both before and after LNT from a Euro 6 diesel vehicle on a chassis dynamometer. The vehicle was repeatedly driven according to the new European driving cycle (NEDC) and the world-harmonized light-duty vehicle test cycle (WLTC) at various ambient temperatures (23, 14 and −5 °C). LNT regeneration was detected twice in the NEDC but 5 times in the WLTC due to the longer period, increased mileage and more frequent acceleration in the WLTC. Accordingly, the NO x conversion rate was higher, and the NO x emission factor was lower for the NEDC than for the WLTC. Additionally, as the ambient temperature decreased, the NO x concentration increased considerably. Because of the poor mixing of fuel and air and the reduced combustion efficiency and stability, the exhaust gas recirculation (EGR) rates decreased. Because the LNT did not reach the light-off temperature (LOT) in the cold start phase, the chemical reactions in the LNT did not occur, and only NO was detected. For the LNT regeneration process, the EGR rates decreased, and the fuel rates increased to release the stored NO x in the LNT. The emissions characteristics of the products, such as NO, NO 2 , N 2 O and NH 3 , during regeneration varied depending on the stored NO x , the after-treatment temperature, and the vehicle driving condition. The results from this comparative study can contribute to monitoring the NO x emission characteristics and optimizing the engine management system to meet future emission regulations including WLTC and low ambient temperature conditions.

Since the Euro 5 regulation was implemented, increasing numbers of Light-Duty (LD) diesel vehicles are being equipped with Diesel Particulate Filter (DPF). Inherently, if a DPF is filled with soot and Particulate Matter (PM), then the DPF must be regenerated periodically. Therefore, this study investigates how an active regeneration process influences the emissions of gases and the size-resolved particle emissions from LD diesel vehicles. The experimental apparatuses were installed to measure the exhaust gas emissions during regeneration events. Two Fast particle analyzers (DMS-500) were positioned upstream and downstream of the DPF to measure the PN concentration and particle size distribution. X-ray Photoelectron Spectroscopy (XPS) was used to investigate the elemental composition and chemical state information of the collected soot samples during regeneration. The experimental results showed that during an active regeneration, the post-injection rate increased, and the post injection timing was significantly retarded, which caused the peak pressure of the cylinder and the thermal efficiency to decrease and the exhaust temperature to increase. According to the upstream PN results, a large increase in the number of nucleation particles occurred during an active regeneration due to the retarded and increased post-injection process. In contrast, the accumulation mode particles measured downstream of the DPF had a majority of total particles during a regeneration because of the increased exhaust temperature, which caused the nucleation mode particles to be easily oxidized.

The purpose of this study was to investigate particle emission characteristics from a spark ignition direct injection (SIDI) engine fueled with ethanol–gasoline blends. Particulate matter (PM) from internal combustion engine is a complex mixture of substances deemed harmful for the human body. Consequently, they are regulated by stringent legislation. According to the Euro-6 regulation, the standard for particle number (PN) emissions of SIDI vehicles is 6.0 × 10 11 N/km. Recent studies have reported that SIDI engines, renowned for their feasibility in reducing CO 2 emissions, could produce excessive amounts of PM due to its structural characteristics. For this reason, there have been many studies on reducing PM emissions from SIDI engines to satisfy strict emission standards. Because ethanol contains an oxygen atom in each molecule, it has a significant influence on combustion performance and characteristics of vehicular discharge, including PM. This study focused on the effect of intermediate ethanol blends from E0 (pure gasoline fuel) to E20 (gasoline fuel with 20% volume of ethanol) on engine performance, size-resolved particle emissions, and engine startability. Particle emission characteristics including particle number and size distribution at part-load test and start performance were investigated with operation points, fuel pressure and injection timing.

In this study, the regulated, particulate, and unregulated emissions, and the fuel economy (FE) from a direct injection spark ignition (DISI) vehicle were investigated on a chassis dynamometer. Two vehicle test cycles, the congested urban (NIER03) and rural modes (NIER09), which reflect vehicle driving patterns in Korea, were tested with varying ethanol contents of gasoline (E0), and low- (E10), medium- (E30 and E50), and high-ethanol blended fuels (E85). The particle number (PN) concentration from E0 was substantially reduced by one or two orders of magnitude with medium- or high-ethanol blended fuels, respectively. The E10 fuel showed the highest PN concentration because of the physicochemical mixture properties of the azeotropic characteristics. As the ethanol fraction increased, the particle sizes shifted to smaller sizes that were dependent on the vehicle test modes and oxygen proportions in the fuels. The regulated and unregulated emissions showed close relationships with the vehicle test modes and ethanol blends. Vehicle running with frequent idle-stops at an extremely low speed and dynamic transient driving under NIER03 showed higher BTEX emissions than the NIER09 mode, and produced lower emission levels due to the higher oxygen and lower aromatic proportions of the ethanol blends. Compared to the NIER03 mode, the CO2 emissions and FEs under the NIER09 mode were substantially improved, with a higher vehicle speed and more energy efficient engine operation points. The low energy contents of the E85 fuel resulted in slight increases in the CO2 emissions and reductions in the FEs of the NIER modes.

The nanoparticle emissions from gasoline direct-injection engines are of concern because of the high particle number concentrations compared with those from a gasoline port fuel injection engine. A gasoline particulate filter is a potential solution for reducing the particulate matter emissions. In this study, a 2.0 l turbocharged gasoline direct-injection vehicle with a metal-foam-type gasoline particulate filter was tested using the New European Driving Cycle and steady vehicle operating conditions. The particle number concentration, the particle-size distribution and the filtration efficiency were determined using a condensation particle counter and a fast response differential mobility spectrometer (DMS500). The particle number emissions (particle numbers per vehicle travelling distance (particles/km)) over the New European Driving Cycle were 1.95 × 1012 particles/km for a base vehicle equipped with a three-way catalytic converter and 5.68 × 1011 particles/km for the additional installation of a gasoline particulate filter on the base gasoline direct-injection vehicle. The filtration efficiency of the particle number and the particulate matter mass reached approximately 71% and 67% respectively. The nucleation-mode particles in the size range less than 23 nm for the gasoline direct-injection vehicle equipped with a three-way catalytic converter were further reduced on installation of a gasoline particulate filter at the downstream position of the three-way catalytic converter. A sharp pressure drop between the gasoline particulate filter of 21.0 mbar was obtained at a vehicle speed of 120 km/h in the New European Driving Cycle. The exhaust gas temperature before the gasoline particulate filter reached around 380–610 °C at steady vehicle speeds of 60–120 km/h. The installation of the gasoline particulate filter has the potential to satisfy the Euro 6c particle number emissions regulations for light-duty gasoline direct-injection vehicles.

This study evaluated the pollutants and nanoparticles, the fuel economy and the levels of carbon dioxide emissions of vehicles equipped with a 1.6 l direct-injection spark ignition engine fuelled by gasoline or by liquefied petroleum gas. The nanoparticles were analysed using a particle measurement system that is used in Europe for regulatory purposes. A fast-response particle size and number spectrometer (model DMS500) were used to characterize the size-resolved particle distributions. The vehicle was tested on a chassis dynamometer for the New European Driving Cycle and Federal Test Procedure 75 in its factory default state (gasoline version) and modified state (for liquefied petroleum gas fuel), and the results were compared. The liquefied-petroleum-gas direct-injection vehicle emitted significantly lower levels of total hydrocarbons than did the gasoline direct-injection vehicle. However, the levels of nitrogen oxide emissions from the liquefied-petroleum-gas direct-injection vehicle were equivalent to those from the gasoline direct-injection vehicle. Because of the higher combustion and exhaust temperatures and relatively higher loads imposed during the driving cycles, the liquefied-petroleum-gas direct-injection vehicle showed a slightly higher level of nitrogen oxide emissions. The particle emissions from the vehicles were mainly affected by the vehicle driving conditions of the test driving cycles. In particular, the particle emissions from the vehicle were pronounced in the cold-start and accelerating phases of the emission certification standards. The nanoparticles from the liquefied-petroleum-gas direct-injection vehicle were significantly fewer in number, exhibiting a reduction of over 99%.

In order to satisfy stringent future emission regulation in diesel engines, systematic approaches to mitigate the harmful exhaust emissions were developed, such as engine hardware, fuel injection equipment, engine control, and after-treatment system. In this study, to improve the nano-particle and NOx emissions from a state-of-the-arts diesel engine, effect of various EGR and fuel injection pressure with combustion analysis were evaluated. Size-resolved nano-particle and NOx emissions showed trade-off characteristics with various EGR rate and increment of fuel injection pressure. Key words :EGR(배기재순환), NOx(질소산화물), Nano-particle(입자상물질), Fuel injection pressure(연료분사압력), Diesel engine(디젤엔진) Nomenclature 1) IMEP : indicated mean effective pressure, barBMEP : brake mean effective pressure, barMBF : mass burned fraction, % 1. 서 론 자동차에서 배출되는 배기가스는 대기오염의 주요한 원인으로써, 세계적으로 자동차에서 배출되는 배기가스 규제를 점점 강화하는 추세이다. 자동차에서 배출되는 질소 산화물 및 입자상 물질은 중추 신경 및 호흡기를 자극하고 산성비 및 대기 중에서 * Corresponding author, E-mail: spark@korea.ac.kr

Mobile source air toxic (MSAT) emissions from a direct injection spark ignition (DISI) passenger vehicle fueled with gasoline and liquid phase liquefied petroleum gas (LPG) were compared using a chassis dynamometer under several in-use vehicle driving conditions. For operation of a dedicated LPG-DI engine, low-pressure fuel systems were specially installed and various engine control parameters were recalibrated considering different chemical properties of LPG. A series of the National Institute of Environmental Research (NIER) modes for determining the emission factors of in-use vehicles in Korea were chosen to quantify not only the regulated emissions with particles but also the unregulated emissions of carbonyls, BTEX, and PAHs from a DISI light-duty vehicle (LDV) with gasoline and LPG. The regulated and particle emissions of LPG-DI vehicles showed strong reduction, and the proportions of sub-23 nm particles were 32–35% in gasoline and 50–65% in LPG. The results revealed that the levels of the MSAT emissions from a DISI engine were closely related to the driving patterns and the fuel properties. A substantial reduction of regulated emissions, particulates, BTEX, and particle-bound PAH emissions was achieved from a LPG-DI vehicle in real driving conditions. Carbonyl compounds acetaldehyde and acrolein showed significant increment from a LPG-DI vehicle.

This paper presents a review of the characterization of physical properties, morphology, and nanostructure of particulate emissions from internal combustion engines. Because of their convenience and readiness of measurement, various on-line commercial instruments have been used to measure the mass, number, and size distribution of nano-particles from different engines. However, these on-line commercial instruments have inherent limitations in detailed analysis of chemical and physical properties, morphology, and nanostructure of engine soot agglomerates, information that is necessary to understand the soot formation process in engine combustion, soot particle behavior in after-treatment systems, and health impacts of the nano-particles. For these reasons, several measurement techniques used in the carbon research field, i.e., highresolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy, were used for analysis of engine particulate matter (PM). This review covers a brief introduction of several measurement techniques and previous results from engine nano-particle characterization studies using those techniques.

This paper is review of the characterization of exhaust particles from state-of-the-art internal combustion engines. We primarily focus on identifying the physical and chemical properties of nano-particles, i.e., the concentration, size distribution, and particulate matter (PM) morphology. Stringent emissions regulations of the Euro 6 and the LEV III require a substantial reduction in the PM emissions from vehicles, and improvements in human health effects. Advances in powertrains with sophisticated engine control strategies and engine after-treatment technologies have significantly improved PM emission levels, motivating the development of new particle measurement instruments and chemical analysis procedures. In this paper, recent research trends are reviewed for physical and chemical PM characterization methods for gasoline and diesel fueled engines under various vehicle certification cycles and real-world driving conditions. The effects of engine technologies, fuels, and engine lubricant oils on exhaust PM morphology and compositions are also discussed.

This study explores the carbon dioxide (CO2) emissions reduction potential of passenger vehicles in Republic of Korea, by assuming a number of CO2 reduction routes. Historical data pertaining to important factors affecting the CO2 emissions of passenger vehicles, such as the number of registered vehicles, annual mileage, and average CO2 emissions per vehicle, were analyzed to predict the extent by which these factors would change in 2020. The results show that the total CO2 emissions from passenger vehicles in 2015 would be approximately 37.1 Mton, assuming automobile manufacturers will meet the regulations for CO2 emissions reductions for 2015. The CO2 emissions reduction route is determined in accordance with a hypothetical regulation for CO2 emissions reductions in 2020. If the CO2 emissions rates of new passenger vehicles are reduced by 3–7% per year after complying with the 2015 regulation, then total CO2 emissions and required energy would be approximately 36.5–38.6 Mton and 12.9–13.6 Mtoe, respectively. Also, if the current fuel economy competition persists until 2020, the CO2 emissions reductions will follow the plausible reduction route and consequently reach 35.1 Mton CO2 and 12.4 Mtoe energy in 2020. As a result, in order to reduce the total CO2 emissions of passenger vehicles in 2020 (compared with 2015), the value of regulated CO2 emissions in 2020 should be set to less than 103 g/km per passenger vehicle.

This study was focused on experimental comparisons of the effects of various vehicle certification modes on the nano-particle and regulated emission characteristics of light duty vehicles with gasoline, diesel particulate filter (DPF) diesel, liquefied petroleum gas (LPG) and non-DPF diesel. The particulate matter, regulated emissions, and CO 2 emission of various fueled vehicles were analyzed with the golden particle measurement system, as recommended by the particle measurement program. The solid particles with a diameter above 23 nm, which in only non-volatile, were measured using a particle number counter (CPC). The vehicle tests were performed on the federal test procedure-75 (FTP-75) and the new European driving cycle (NEDC) mode, and the results were compared to evaluate particle formation with both CPC and a differential mobility spectrometer (DMS500). Particle formation was highly dependent on the vehicle speed and load conditions of each mode. In particular, the particle numbers of conventional fuels sharply increased during cold start, fast transient acceleration, and high-load operation phases of the vehicle emission tests. The DPF diesel vehicle fitted with a particulate filter showed substantial reduction of particulate matter whose number concentration was equivalent to those of gasoline and LPG fueled vehicles. It was found that particle emission and regulated emissions as well as CO 2 emission, and fuel economy were closely related with vehicle driving patterns and fuel composition, simultaneously. Finally, sub-23 nm nucleation mode particles using DMS500 were majority in the gasoline and LPG vehicles, whereas accumulation mode particles were mainly discharged in the diesel vehicles.

The particulate emissions generated from a side-mounted 2.4 L gasoline direct injection (GDI) engine were evaluated using a metal foam-type gasoline particulate filter (GPF), placed on the downstream of a three-way catalyst. An ULEV legislation-compliant light-duty vehicle was tested under the new European driving cycle (NEDC) and at constant-speed driving conditions. Particle number (PN) concentrations, particulate size distribution and the filtration efficiency of the GPF were evaluated with the condensation particle counter (CPC) and the differential mobility spectrometer (DMS). The PN emissions for the entire NEDC were 1.17E+12 N/km for the base GDI vehicle and 4.99E+11 N/km for the GPF-equipped GDI vehicle, and the filtration efficiency of the GPF was 57%. In particular, the number of sub-23 nm particles formed in the GDI vehicle was substantially reduced, with 97% efficiency. The pressure drop in the metal foam-type GPF was constrained to be below 1.0 kPa at a 120 km/h vehicle speed, and as a result, the fuel economy and the CO 2 emission for the GPF-applied vehicle were equivalent to those for the base vehicle.

This study investigates the time resolved total hydrocarbon (THC) and nano-particle emission characteristics of liquid phase LPG direct injection (LPG-DI) engines during the cold start and during fast-idle operation state. The fuel circuit for the direct injection of LPG fuel was converted from a returnless-type into a return-type system to evaluate the cold start performance of a dedicated LPG-DI engine. To improve the engine-out THC as well as nano-particle emissions and catalyst light-off behavior during the cold start phase, the effect of various spark timings and excess air ratio were investigated using a fast response THC analyzer, combustion analyzer, and differential mobility spectrometer (DMS). The combustion stability, cycle-to-cycle THC, light-off temperature (LOT) of the catalyst, and nano-particle emission characteristics were evaluated during the cold start and warm-up phase of the LPG-DI engine. The experimental results showed that the retarded spark timing after the top dead center (TDC) and lean operation have advantage to improve the time resolved THC, LOT, and combustion characteristics in the cold start condition. The cumulative THC reduction rate during 30 s was about 25–43% and the light-off times of the catalyst were shortened by 25–31 s as the retarded spark timing after TDC.

This investigation focused on the particle emission characteristics of a heavy-duty diesel engine and the effects of after-treatment systems such as diesel particulate filter and selective catalytic reduction. The test engine was operated on the worldwide harmonized transient cycle mode, which is a new transient cycle for Euro 6, and the conventional European transient cycle mode. Four combinations of after-treatment systems, engine-out, selective catalytic reduction, diesel particulate filter, and diesel particulate and nitrogen oxide reduction, were evaluated for the transient cycles, respectively. The whole test procedure, as part of the Korea particulate measurement programme and the inter laboratory correlation exercise for domestic heavy-duty diesel engines, complied with the recommended method of particulate measurement programme. The particles that were extracted through the golden particle measurement system the constant volume sampler tunnel consisted of solid particles like carbonaceous fraction, metal ash, etc. The particles emitted from the tail-pipe, as analyzed by the differential mobility spectrometer, included volatile or soluble particles like sulphate fraction, nitrate fraction, and organic fraction. The test results showed that the particle number and size distribution depended on the catalytic activity or filtration efficiency of the after-treatment system. Compared to the accumulation mode, the nucleation mode was easily caught or oxidized by the after-treatment system. Additionally, the nucleation mode was sharply increased by excessive ammonia injection because nitrogen dioxide-assisted diesel particulate filter regeneration resulted in reduced conversion efficiency of the selective catalytic reduction.

In this study, to evaluate the potential of a dedicated liquefied petroleum gas-direct injection (LPG-DI) vehicle, regulated and unregulated emissions from a light-duty gasoline direct injection (GDI) vehicle were compared. The vehicle tests were performed on a chassis dynamometer with constant volume sampler (CVS) over the federal test procedure (FTP)-75, highway fuel economy test (HWFET), and new European driving cycle (NEDC), which include the engine starting, transient and warm-up operation. The emissions of total hydrocarbon (THC) as well as nitrogen oxides (NOx) and nano-particles from the LPG-DI vehicle showed significantly superior performance relative to gasoline with excellent gaseous mixture preparation and low carbon fuel. The CO 2 emission of the LPG-DI vehicle decreased approximately 4–6% compared to the GDI vehicle. Aldehydes formation was influenced by vehicle test modes, such as the proportions of vehicle low speed patterns as well as long idle duration and the inclusion of engine warm-up periods. Formaldehyde, acetaldehyde, and acrolein compounds significantly increased with the LPG-DI vehicle, and this increase was related with partial oxidation during the combustion process of butane and propane. Except for the slightly increase in the HWFET mode, strong decreases in BTEX were observed with the application of LPG fuel in the FTP-75 and NEDC mode. It was found that the regulated and unregulated emissions were closely related to both the vehicle driving patterns and fuel compositions.

Lean NOx Trap (LNT) catalysts are capable of reducing exhaust NOx emissions from diesel engines. LNT stores NOx in lean condition and exhausts N2 by reducing NOx in rich condition. NOx reduction characteristic of LNT catalysts using throttle position sensor and fuel injection timing control for light-duty diesel engine was investigated. In contrast to SCR system, LNT catalyst uses diesel fuel in resuctant. Also if the concentration of reductant is exceeded, excessive amount of reductant will slip throughout LNT and cause another emission problem. Thus LNT regeneration with precise engine control established that can make higher NOx conversion efficiency and lower fuel penalty, prevent another emission problem. NOx and reductant concentration were measured by the NOx sensor and Mexa7100D equipped inlet and outlet of catalyst. As a result of engine test, regeneration strategy has reached high of 77.8% NOx conversion efficiency according to engine operation condition. Moreover, we have proved that it is possible to use regeneration strategy of LNT within 5% fuel penalty.

Time-resolved nanoparticle number concentrations and size distribution characteristics were investigated in gasoline direct-injection vehicles, according to fuel preparation methods. Particle number emissions were measured using the golden particle measurement system recommended by the Particle Measurement Programme, and the particle size spectrum was determined using a DMS500 spectrometer installed at the tailpipe of the vehicles. The wall-guided gasoline direct-injection vehicle exhibited the most temperature-dependent nanoparticulate matter exhaust characteristics, owing to direct accumulation of fuel on the piston head and cylinder liner and a high concentration of accumulation mode particles. The air-guided gasoline direct-injection vehicle emitted particle emissions mostly during cold transient driving conditions and high acceleration, which had a weak trimodal characteristic with evenly distributed nucleation and accumulation mode particles. The spray-guided gasoline direct-injection vehicle continuously discharged 105 particles/cm3 during constant-speed driving segments, because of the ultra-lean-burn operation and bulk quenching; particulate matter from the spray-guided gasoline direct-injection vehicle demonstrated a strong bimodal characteristic, spreading over 10–100 nm. The particle number emissions for the gasoline direct-injection vehicles for the New European Driving Cycle test mode were 1.48 × 1012 particles/km, 6.03 × 1011 particles/km and 3.17 × 1012 particles/km for the wall-guided type, the air-guided type and the spray-guided type respectively, and none of these were able to satisfy the proposed particle number regulations for the Euro 6 standard. For gasoline direct-injection vehicles, it should be considered that engine hardware modifications, as well as energy management system calibrations and even the application of the particle filter, may be needed to meet the upcoming particulate matter number regulation.

Cooled EGR system is widely used to reduce NOx emissions in diesel engine. But when EGR rate was increased, combustion stability was worsened and PM level was increased. So determining optimized control point of EGR rate is important. In order to determine this point, it is important to figure out the effect of EGR system on the exhaust emissions. In this research, NOx and PM emissions were analyzed with various coolant temperature supplied to the EGR cooler at several positions such as downstream of turbocharger, upstream and downstream of DPF. Effects of some variables such as EGR rate, hot / cooled EGR and change of injection timing were estimated. And CO 2 emissions were measured at exhaust and intake manifold to calculate EGR rate at each engine operating condition. Also combustion analysis was performed in each engine operating conditions. In the result of this study, there was trade-off between NOx emissions and PM emissions. When EGR rate was increased, combustion pressure was decreased and COV of IMEP was increased.

To evaluate the potential of a dedicated direct injection liquefied petroleum gas (LPG-DI) vehicle, we investigated several engine control parameters that are closely related to the characteristics of mixture preparation and nano-particle emissions. The fuel supply circuit for the direct injection of LPG in liquid form was modified into a return-type system comprised of a three-way high pressure pump, a low pressure regulator, a brushless direct current (BLDC) pump, and an LPG tank. Particulate number (PN) and size distribution measurements were performed in FTP-75 and HWFET modes, and also using an engine test bench. The experimental results showed that significant PN emissions were produced during the cold start and the transient warm-up operations of the gasoline direct injection (GDI) vehicle; this production of particle emissions was due to application of split injection and catalyst heating function. A bimodal particle size of 10

이에 현재 시중에 판매되고 있는 GDI 차량 Key Words: GDI(가솔린직접분사), DMS(고속 PM 분석기), HFR-400(고속 THC 분석기), CLD-400(고속 NOx 분석기), THC(미연탄화수소), NOx(질소 산화물), PM(입자상 물질) 초록: 본 논문에서는 GDI 엔진의 냉각수 온도에 따른 연소 및 배출가스 특성을 연구하였다. 엔진에서 나오는 입자상 물질의 수와 크기 분포는 DMS-500 장비로 측정하였다. 배기포트 에 장착된 CLD-400 과 HFR-400 을 통해 NOx 및 THC 의 배출 특성을 연소주기 별로 측정하였다. 결과적으로 낮은 냉각수온에서 5~10 nm 의 입자상 물질이 크게 증가하는 특성을 보였다. THC 또한 낮은 냉각수온에서 증가하는 특성을 보였는데 이는 연소실 내 연료의 액막현상 때문이다. 그리고 NOx 는 높은 냉각수온에서 감소하는 특성을 보였는데 이는 내부 EGR 이 증가하기 때문이다. 결론적으로 THC 와 NOx 그리고 입자상 물질의 배출을 줄이기 위해서는 냉각수온을 빠르게 올리는 EMS 변수 설정 필요하다. Abstract: This paper investigated the combustion and exhaust gas characteristics of gasoline direct injection engines for various cooling water temperature. The engine-out nanoparticle emission number and size distribution were measured by a DMS-500 equipped upstream of the catalyst. A CLD-400 and an HFR-400 were equipped at the exhaust port to analyze the cyclic NOx and total hydrocarbon emission characteristics. The results showed that the nanoparticle emission number greatly increased at low coolant temperatures and that the exhaust mainly contained particulate matter of 5–10 nm. THC also increased under low temperature conditions because of fuel film on the combustion chamber. NOx emissions decreased under high temperature conditions because of the increase in internal exhaust gas recirculation. In conclusion, an engine management system control strategy for driving coolant temperature up rapidly is needed to reduce not only THC and NOx but also nanoparticle emissions.

This study was conducted for the experimental comparison of particulate emission characteristics between the European and World-Harmonized test cycles for a heavy-duty diesel engine as part of the UN/ECE PMP ILCE of the Korea Particulate Measurement Program. To verify the particulate mass and particle number concentrations from various operating modes, ETC/ESC and WHTC/WHSC, were evaluated. Both will be enacted in Euro VI emission legislation. The real-time particle emissions from a Mercedes OM501 heavy-duty golden engine with a catalyst based uncoated golden DPF were measured with CPC and DMS during daily test protocol. Real-time particle formation of the transient cycles ETC and WHTC were strongly correlated with engine operating conditions and after-treatment device temperature. The higher particle number concentration during the ESC #7 to #10 mode was ascribed to passive DPF regeneration and the thermal release of low volatile particles at high exhaust temperature conditions. The detailed average particle number concentration equipped for golden DPF reached approximately 4.783E+11 #/kWh (weighted WHTC), 6.087E+10 #/kWh (WHSC), 4.596E+10 #/kWh (ETC), and 3.389E+12 #/kWh (ESC). Particle masses ranged from 0.0011 g/kWh (WHSC) to 0.0031 g/kWh (ESC). The particle number concentration and mass reduction of DPF reached about 99%, except for an ESC with a reduction of 95%.

Key Words: PM(입자상물질), DPF(매연여과장치), EGR(배기재순환), DMS(고속입자상물질측정장치),NucleationMode(핵화모드),AccumulationMode(축적모드)초록: 본연구는승용디젤엔진의입자상물질배출특성에관한것으로써, 엔진에서배출된입자상물질이배기관및후처리장치인디젤산화촉매와매연여과장치를통과할때의특성변화를파악하기위하여후처리장치각각전 후단및배기관에서직접측정하였다.또한다양한엔진회전속도및부하조건에서측정함으로써입자상물질배출맵을구축하였으며,디젤산화촉매및매연여과장치의입자상물질저감효과에대해평가하였다.뿐만아니라배기재순환율과연료분사시기를변경시켜입자상물질의배출특성변화를파악하였다.모든시험에서입자상물질을5~1000nm크기까지측정할수있는DMS500을이용하였다.Abstract: Inthisstudy,wemainlyfocusedonthePM(ParticulateMatter)emissioncharacteristicsofadieselengine.To analyze particle behavior in the tail-pipe, particle emission was measured on the engine-out (downstream ofturbocharger), each upstream and downstream both of DOC (Diesel Oxidation Catalyst) and DPF (Diesel ParticulateFilter). Moreover, particle emission contours on each sampling point were constructed. The reduction efficiency ofparticlenumberconcentrationandmassthroughtheDOCandDPFwasstudied.ParameterssuchasEGR(ExhaustGasRecirculation) and the main injection timing were varied in part load conditions and evaluated using the engine-outemissions. TheDMS500(Differential MobilitySpectrometer) wasusedasaparticlemeasurement instrument that canmeasure particle concentrations from5 nmto 1000 nm. Nano-particles of sizes less than 30 nmwere reduced byoxidationorcoagulatedwithsolidparticlesinthetail-pipeandDOC.TheDPFhasaveryhighfiltrationefficiencyoveralloperatingconditionsexceptduringnaturalregenerationofDPF.

The objective of this work presented here was experimental study of steadystate and cold start exhaust nano-sized particle characteristics from common rail diesel engine. The effect of the diesel oxidation catalyst (DOC) on the particle number reduction was insignificant, however, particle number concentration levels were reduced by 3 orders of magnitude into the downstream of diesel particulate filter (DPF). In high speed and load conditions, natural regeneration of trapped particle occurred inside DPF and it was referable to increase particle number concentration. As fuel injection timing was shifted BTDC to ATDC , particle number concentration level was slightly reduced, however particle number and size was increased at ATDC . Nucleation type particle reduced and accumulation type particle was increased on EGR condition.

Selective Catalytic Reduction (SCR) system is a high-effective NOx reduction technology in diesel engines. As the emission standard of diesel engines is more stringent, vehicle manufactures makes efforts on emission technologies. This paper discusses the performance of Urea-SCR system according to the engine operating conditions in a passenger diesel engine. Engine test results in this paper show that it is important to consider the catalyst temperature and space velocity to obtain high NOx conversion efficiency. In condition of high catalyst temperature, over 90% NOx conversion efficiency is indicated. However, when catalyst temperature is low, NOx conversion efficiency was decreased. Also, it was shown that space velocity mainly effects on the DeNOx performance under 220 degree celsius of SCR catalyst temperature. As the urea injection pressure was decreased, NOx conversion efficiency was declined. It is concerned about urea droplet atomization. This work shown in this paper can lead to improved overall NOx conversion efficiency.

This study was focused on experimental comparisons of the effects of various vehicle certification modes on particle emission characteristics of light-duty vehicles with gasoline, diesel, LPG, and low-carbon fuels such as bio-diesel, bioethanol, and compressed natural gas, respectively. The particulate matter from various fueled vehicles was analyzed with the golden particle measurement system recommended by the particle measurement programme, which consists of CVS, a particle number counter, and particle number diluters. To verify particle number and size distribution characteristics, various vehicle emission certification modes such as NEDC, FTP-75, and HWFET were compared to evaluate particle formation with both CPC and DMS500. The formation of particles was highly dependent on vehicle speed and load conditions for each mode. In particular, the particle numbers of conventional fuels and low-carbon fuels sharply increased during cold start, fast transient acceleration, and high-load operation phases of the vehicle emission tests. A diesel vehicle fitted with a particulate filter showed substantial reduction of particulate matter with a number concentration equivalent to gasoline and LPG fuel. Moreover, bio-fuels and natural gas have the potential to reduce the particulate emissions with the help of clean combustion and low-carbon fuel quality compared to non-DPF diesel-fueled vehicles.

The effect of ethanol-blended gasoline fuels on the characteristics of time-resolved particle concentration and size distribution was investigated in a gasoline engine and in a flexible fuel vehicle. Particle concentration levels from the vehicle running on ethanol-blended gasoline were compared to those of diesel vehicles with and without diesel particulate filter (DPF). In the engine test, particle size distribution and number concentration using E0 and E10 fuels were analyzed with a differential mobility spectrometer (DMS500) at dynamic engine operation conditions. In the vehicle emission test, time-resolved particle concentrations with ethanol blending contents (E0, E10, and E85) during a new European driving cycle (NEDC) were analyzed with a golden particle measurement system (GPMS) as recommended by the particle measurement programme (PMP). As the excess air ratio is shifted to lean conditions and as the spark and intake valve opening timing are retarded, particle number levels were reduced with both E0 and E10. The particle concentration from ethanol-blended gasoline was slightly decreased regardless of engine operating conditions. From the driving test results, the total particle concentration from the spark ignition and the diesel vehicle with a DPF was decreased by two orders of magnitude compared to a non-DPF diesel vehicle. As the oxygenated component is increased, particle emissions decreased. The total particle concentration for E85 was reduced by 37% compared to E0.

This paper mainly focused on the comparison of nanoparticle size distribution and number concentration level characteristics with gasoline and diesel fueled light duty vehicles. In the engine research, particle size distribution and number concentrations were analyzed by a DMS500 with engine parameters. Time-resolved particle number concentration levels from test vehicles were measured by a golden particle measurement system (GPMS) as recommended by a Particle Measurement Programme (PMP) on certification modes such as New European Driving Cycle (NEDC), Federal Test Procedure (FTP)-75, and Highway Fuel Economy Test (HWFET). In addition, particle emission characteristics from vehicles were analyzed by DMS500 during transient and high-speed driving conditions. From the results, we found that the formation of particles was highly dependent on vehicle speed and load conditions for each mode. The diesel vehicle equipped with a particulate filter showed substantial reduction of the total particle number whose number concentration was equivalent to that of the gasoline vehicle. The nucleation mode particles from gasoline fuel were mainly emitted; however, the accumulation mode particles from the diesel fuel were generally analyzed.

In SI engines, valve events have a major influence on volumetric efficiency, fuel economy and exhaust emissions. Moreover, swirl and tumble motions in the intake charge also improve combustion speed and quality by stratifying the mixture as well as intensifying the mixing rate of air and fuel. This paper investigates the behaviors of an engine and the combustion phenomenon for various intake valve timings and intake charge motions using CVVT system and port masking schemes. Test condition includes a part load and a cold idle condition inclusive of a cold start of the engine. Time-resolved HC and NOx emissions were also measured at an exhaust port to examine their formation mechanisms and behaviors with fast response HC/NOx analyzers. In conclusion, the fast burning of fuel and improved combustion quality by enhanced charge motions reduced unburned HC emissions, and advancing the intake valve opening reduced HC as well as NOx. Furthermore, HCs during the cold transient phase and idle conditions decreased with recalibrated start parameters such as lean air-fuel ratio and spark retardation via the enhancement of intake charge motions.

The Light Duty Inter-Laboratory Correlation Exercise (ILCE) final report, performed with the ‘PMP Golden Vehicle’ at nine laboratories in the EU, Korea and Japan to demonstrate repeatability and reproducibility of the particle number concentration emissions measurement techniques proposed by the Particle Measurement Program (PMP), was released in 2007. The ILCE was conducted by the Korea Particle Measurement Program (KPMP) with a domestic diesel passenger vehicle equipped with a diesel particulate filter (DPF) between three certification laboratories and the research center of an automotive manufacturer to meet future regulations (EURO 5 and EURO 6) of particle number concentration for light-duty vehicles in early 2008. This research focused on measuring the particulate matter emission (particle number and mass) levels of a representative light-duty diesel passenger vehicle during new European driving cycle (NEDC) mode to analyze the repeatability and reproducibility between laboratories in Korea. From the ILCE test results in Korea, the mean total particle number concentration levels ranged from 5.43E+10 #/km to 1.58E+11 #/km and 0.0003 g/km to 0.0036 g/km for particle mass. Repeatability between participating laboratories ranged from 32% to 66% for particle number, 11% to 70% for particle mass; the reproducibility level was 46% for particle number, and 66% for particle mass emission.

This study is mainly focused on the assessment of return, semi return, and returnless fuel supply system for an LPi engine. In order to compare the return type with returnless one with various LPG blends, combustion analysis and cyclic THC emission characteristic were tested at the part load operating condition of the LPi engine. Considering heat balance of each fuel supply systems, pressure and temperature increment of return type showed lower at the fuel rail during idle warm up operation. However, those of returnless type at LPG tank maintained stable and slow increment because the heat transfer from the LPi engine was minimized. Finally, hot restartability of each fuel supply systems were evaluated with the various LPG blends and fuel temperatures. As a result, semi return type has equivalent performance to return type considering combustion and emission characteristic, hot restartability performance for LPi engine. 1. 서 론 기존 믹서방식 연료공급시스템의 단점을 개선한 LPi(Liquid phase injection) 시스템은 LPG 탱크 내부에 장착된 연료펌프를 이용하여 LPG 연료를 가압 후 연료탱크의 토출부에서부터 인젝터까지 액체 상태를 유지한 다음 이를 전자식 인젝