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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.

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.

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.

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.

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

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 work investigates the total hydrocarbon (THC) emission characteristics in a liquid phase LPG injection (LPLi) engines during cold start operation. To clarify the THC formation mechanism of the LPLi engines, the effect of various spark timings during cold start was investigated using a fast response THC analyzer and combustion analyzer. A cycle-to-cycle combustion analysis showed that the majority of THC emissions are emitted within the first few seconds after engine start. The emission results for vehicle test indicated that exhausted THC during phase 1 of FTP-75 mode decreased by 23% at top dead center (TDC) spark timing and by 31% at after top dead center (ATDC) 10° crank angle (CA) compared to that with a conventional spark timing of before top dead center 10° CA. In addition, catalyst light off times were shortened by 7 and 10 s in case of TDC and ATDC 10° CA spark timings, respectively. Consequently, it was founded that the control strategy of retarding spark timing during cold start in the LPLi vehicle was a very effective method to reduce THC emissions.