Gasoline Direct Injection Vehicles Research Articles

Influence of Ash-Soot Interactions on the Reactivity of Soot from a Gasoline Direct Injection Engine.

Gasoline particulate filters (GPF) are being utilized in certain markets on gasoline direct injection (GDI) vehicles to reduce tailpipe particulate emissions as required by particle number regulations. GPF filtration efficiency is dependent on soot build-up within the filter. Since soot oxidizes within the GPF during normal vehicle operation, an understanding of soot reactivity is important for optimizing aftertreatment architecture and engine calibration. Past work has indicated that gasoline soot reactivity may depend on levels of metallic ash species. In this work, carbonaceous particulate matter from a GDI engine are evaluated from engine operation at a consistent speed and load but with different levels of fuel injection pressures and timings to vary the relative ash to soot ratio. Soot reactivity is found to vary significantly with the ratio of ash to soot present. Interestingly, the more reactive soots possess a unique oxidation profile by which a conventional Arrhenius type expression cannot be used to quantify reactivity. To understand the mechanisms driving such distinct oxidation differences, soot samples are analyzed after being partially oxidized. Particulate characteristics are evaluated by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and scanning transmission electron microscopy with energy dispersive spectroscopy (STEM + EDS). A mechanism is proposed that may explain further why ash affects gasoline soot reactivity to the extent seen in this and other work.

Evaluating the relationships between aromatic and ethanol levels in gasoline on secondary aerosol formation from a gasoline direct injection vehicle

While the effects of fuel composition on primary vehicle emissions have been well studied, less is known about the effects on secondary aerosol formation and composition. The propensity of light-duty gasoline engines to form secondary aerosol and contribute to regional air quality burdens are of scientific interest. This study assessed secondary aerosol formation and composition due to photochemical aging of exhaust emissions from a light-duty vehicle equipped with gasoline direct injection (GDI) engine. The vehicle was operated on eight fuels with varying ethanol and aromatic levels. Testing was performed over the LA92 cycle using a chassis dynamometer. The aging studies were performed using a mobile environmental chamber. Diluted exhaust emissions were introduced to the mobile chamber over the course of the LA92 cycle and subsequently photochemically reacted. It was found that secondary aerosol mass exceeded the primary particulate matter (PM) emissions. Secondary aerosol was primarily composed of ammonium nitrate due to the elevated tailpipe ammonia emissions. The high aromatic fuels produced greater total carbonaceous aerosol and secondary organic aerosol (SOA) compared to the low aromatic fuels. A clear influence of ethanol for the high aromatic fuels on SOA formation was observed, with greater SOA formation for the fuels with higher ethanol contents. Our results suggest that more SOA formation is expected from current GDI vehicles when operated with gasoline fuels rich with heavier aromatics and blended with higher ethanol levels.

Correlation analysis of road load fuel economy variations by energy difference for gasoline direct injection and diesel-powered vehicles

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.

Comparative Investigation of Gaseous Emissions and Particle Emission Characteristics from Turbo-Charged Direct Injection (DI) Engine with Gasoline and LPG Fuel Depending on Engine Control Parameters

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.

On-road gaseous and particulate emissions from GDI vehicles with and without gasoline particulate filters (GPFs) using portable emissions measurement systems (PEMS)

This study assessed the on-road gaseous and particulate emissions from three current technology gasoline direct injection (GDI) vehicles using portable emissions measurement systems (PEMS). Two vehicles were also retrofitted with catalyzed gasoline particulate filters (GPFs). All vehicles were exercised over four routes with different topological and environmental characteristics, representing urban, rural, highway, and high-altitude driving conditions. The results showed strong reductions in particulate mass (PM), soot mass, and particle number emissions with the use of GPFs. Particle emissions were found to be highest during urban and high-altitude driving compared to highway driving. The reduction efficiency of the GPFs ranged from 44% to 99% for overall soot mass emissions. Similar efficiencies were found for particle number and PM mass emissions. In most cases, nitrogen oxide (NOx) emissions showed improvements with the catalyzed GPFs in the underfloor position with the additional catalytic volume. No significant differences were seen in carbon dioxide (CO2) and carbon monoxide (CO) emissions with the vehicles retrofitted with GPFs.

Direct Radiative Effect and Public Health Implications of Aerosol Emissions Associated with Shifting to Gasoline Direct Injection (GDI) Technologies in Light-Duty Vehicles in the United States.

Due to their enhanced fuel economy, the market share of gasoline direct injection (GDI) vehicles has increased significantly over the past decade. However, GDI engines emit higher levels of black carbon (BC) aerosols compared to traditional port fuel injection (PFI) engines. Here, we performed coupled chemical transport and radiative transfer simulations to estimate the aerosol-induced public health and direct radiative effects of shifting the U.S. fleet from PFI to GDI technology. By comparing simulations with current emission profiles and emission profiles modified to reflect a shift from PFI to GDI, we calculated the change in aerosol (mostly BC) concentrations associated with the fleet change. Standard concentration-response calculations indicated that the total annual deaths in the U.S. attributed to particulate gasoline-vehicle emissions would increase from 855 to 1599 due to shifting from PFI to GDI. Furthermore, the increase in BC associated with the shift would lead to an annual average positive radiative effect over the U.S. of approximately +0.075 W/m2, with values as large as +0.45 W/m2 over urban regions. On the other hand, the reduction in CO2 emissions associated with the enhanced fuel economy of GDI vehicles would yield a globally uniform negative radiative effect, estimated to be -0.013 W/m2 over a 20 year time horizon. Therefore, the climate burden of the increase in BC emissions dominates over the U.S., especially over source regions.

Potential dual effect of anthropogenic emissions on the formation of biogenic secondary organic aerosol (BSOA)

Abstract. The fraction of gasoline direct-injection (GDI) vehicles comprising the total vehicle pool is projected to increase in the future. However, thorough knowledge about the influence of GDI engines on important atmospheric chemistry processes is missing – namely, their contribution to secondary organic aerosol (SOA) precursor emissions, contribution to SOA formation, and potential role in biogenic–anthropogenic interactions. The objectives of this study were to (1) characterize emissions from modern GDI vehicles and investigate their role in SOA formation chemistry and (2) investigate biogenic–anthropogenic interactions related to SOA formation from a mixture of GDI-vehicle emissions and a model biogenic compound, α-pinene. Specifically, we studied SOA formation from modern GDI-vehicle emissions during the constant-load driving. In this study we show that SOA formation from GDI-vehicle emissions was observed in each experiment. Volatile organic compounds (VOCs) measured with the proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) could account for 19 %–42 % of total SOA mass generated in each experiment. This suggests that there were lower-volatility intermediate VOCs (IVOCs) and semi-volatile organic compounds (SVOCs) in the GDI-vehicle exhaust that likely contributed to SOA production but were not detected with the instrumentation used in this study. This study also demonstrates that two distinct mechanisms caused by anthropogenic emissions suppress α-pinene SOA mass yield. The first suppressing effect was the presence of NOx. This mechanism is consistent with previous reports demonstrating suppression of biogenic SOA formation in the presence of anthropogenic emissions. Our results indicate a possible second suppressing effect, and we suggest that the presence of anthropogenic gas-phase species may have suppressed biogenic SOA formation by alterations to the gas-phase chemistry of α-pinene. This hypothesized change in oxidation pathways led to the formation of α-pinene oxidation products that most likely did not have vapor pressures low enough to partition into the particle phase. Overall, the presence of gasoline-vehicle exhaust caused a more than 50 % suppression in α-pinene SOA mass yield compared to the α-pinene SOA mass yield measured in the absence of any anthropogenic influence.

Non-Structural Damage Verification of the High Pressure Pump Assembly Ball Valve in the Gasoline Direct Injection Vehicle System

The injection pressure of the gasoline direct injection vehicle is currently developing from the low pressure to the high pressure, and the increase of the injection pressure has brought various damage problems to the high pressure pump structure. These problems should be solved urgently. In this paper, the damage problem of the high pressure pump unloading valve ball in a gasoline direct injection vehicle under high pressure conditions is studied. The theoretical calculation of the force of the pressure relief valve is carried out. Firstly, the equivalent friction coefficient is obtained by decoupling analysis of the statically indeterminate model. Based on this, a finite element model is established. The equivalent stress is obtained by numerical simulation. The equivalent stress is compared with the yield strength of the valve ball material to determine that the valve ball damage is a non-static damage. At the same time, the s-N curve of the probability of destruction of one-millionth of the material of the valve ball is given. Then, the fatigue numerical simulation is performed. A safety factor of 3.66 is obtained. In summary, the high pressure relief valve ball in the direct injection high pressure pump should not be a traditional structural damage under high pressure conditions. In the theoretical calculation, the tangential displacement and radial displacement of the ball are all on the micrometer level. It can be presumed that the surface damage of the valve ball is microscopic damage, such as fretting wear.

Particle number (PN) emissions from gasoline, diesel, LPG, CNG and hybrid-electric light-duty vehicles under real-world driving conditions

The current experimental study presents solid (non-volatile) particle number emissions with a size cut-off at 23 nm (SPN23, referred to as PN hereinafter) under real-world driving conditions for 8 passenger cars powered by diesel, gasoline, Liquefied Petroleum Gas (LPG), Compressed Natural Gas (CNG) and hybrid-electric powertrains. The objective was to identify the highest emitters and assess whether PN focus should be extended to engine and fuel types other than diesel and gasoline direct injection (GDI). Results (under the cold-start RDE-compliant route) show that a Euro 6b gasoline vehicle equipped with port fuel injection (PFI) engine, comprised the highest PN emitter (4.5 times higher than the Euro 6 limit of 6 × 1011 p/km), while similar emission levels (up to 3.7 times higher than this limit) were detected in the older-technology (Euro 3 and 4) gasoline and (retrofitted) LPG PFI vehicles. This limit was also exceeded (by 1.7 times) by one gasoline direct injection (GDI) Euro 6b non-GPF vehicle. PN emissions from the hybrid-electric vehicle (equipped with gasoline PFI engine) were lower than the other Euro 6b PFI vehicle, but still high compared to typical PFI engines found in literature. The lowest emissions were detected in diesel and CNG engines (as low as 7.8 × 109 and 2.4 × 1010 p/km respectively). Euro 6b LPG vehicle was found to be a low emitter (3.3 times lower than the 6 × 1011 p/km limit), while similar emission levels were detected in the other Euro 6b non-GPF GDI vehicle. Among the different driving sections (urban, rural, motorway), urban and especially the cold phase had the highest contribution in most cases. Finally, a significant PN reduction potential was observed with LPG and CNG over gasoline (up to 93% and 90% respectively), although the opposite trend was detected in an old-technology retrofitted LPG vehicle. These results indicate that close attention should be focused on other engine and fuel types, apart from diesel and GDI. Regulatory initiatives towards air pollution reduction should include measures for the reduction of high-emission old-technology gasoline and LPG vehicles, while modern gasoline PFI engines should also be further scrutinized.

Intermediate and high ethanol blends reduce secondary organic aerosol formation from gasoline direct injection vehicles

We evaluated the secondary aerosol formation from two current technology flex fuel vehicles (FFVs) equipped with gasoline direct injection engines when operated on different fuel formulation on a chassis dynamometer. This study explored the influence of ethanol fueling and aromatic concentration on secondary organic aerosol (SOA) production by utilizing two E10 fuels with different aromatic levels and two higher ethanol blends (i.e., E30 and E78). The diluted emissions from both FFVs were photooxidized in a 30 m3 mobile atmospheric chamber with two distinct initial conditions, while the vehicles operated over cold-start and hot-start LA92 test cycles. Testing revealed that one vehicle did not produce secondary aerosol when emissions were photooxidized with a single precursor oxidant. However significant SOA formation occurred in the presence of an anthropogenic volatile organic carbon surrogate and NOx mixture in the chamber, despite the fact that both vehicles had similar primary particulate emission levels. The secondary aerosol formed in an urban airshed was mainly composed of ammonium nitrate and significantly exceeded primary tailpipe PM emissions. Cold-start operation from both vehicles led to greater secondary aerosol production compared to hot-start LA92 operation. SOA production showed a strong relationship with the tailpipe non-methane hydrocarbon (NMHC) emissions and overall reduced with higher ethanol blending in the fuel. The impact of aromatics was clear, with the higher aromatic E10 fuel showing higher SOA formation than the lower aromatic E10 fuel.

Effects of fuel-injection systems on particle emission characteristics of gasoline vehicles

In this study, the particle emission characteristics of gasoline vehicles with four different types of spark ignition engines, i.e., port fuel-injection (PFI), 150-bar side-mounted gasoline direct-injection (GDI), 200-bar side-mounted GDI, and 200-bar center-mounted GDI vehicles, were evaluated using Federal Test Procedure-75 (FTP-75) and worldwide harmonized light vehicles test cycle (WLTC). Particulate matter (PM), particle number (PN), and organic carbon/elemental carbon ratio (OC/EC) were evaluated using a PM holder, a solid particle counting system, and an OC/EC analyzer. The results of the PM and PN emissions tests indicated that GDI 200-bar vehicles emitted less than GDI 150-bar vehicles, and center-mounted vehicles emitted less than side-mounted vehicles. PFI vehicles showed 15% higher PN emission rates compared with GDI vehicles during acceleration conditions in FTP-75 mode. Additionally, PN emissions in WLTC hot mode indicated that speed affects PFI vehicles more than GDI vehicles. Furthermore, PFI vehicles did not show significant PN emissions in a low-speed phase, even at high acceleration. PFI vehicles showed 15% higher PN emission rates compared with GDI vehicles while accelerating in FTP-75 mode. PFI and GDI side-mounted vehicles showed higher OC emission rates in hot mode than in cold mode.

Laboratory and On-Road Evaluation of a GPF-Equipped Gasoline Vehicle

The introduction of a solid particle number limit for vehicles with gasoline direct injection (GDI) engines resulted in a lot of research and improvements in this field in the last decade. The requirement to also fulfil the limit in the recently introduced real-driving emissions (RDE) regulation led to the introduction of gasoline particulate filters (GPFs) in European vehicle models. As the pre-standardisation research was based on engines, retrofitted vehicles and prototype vehicles, there is a need to better characterise the actual emissions of GPF-equipped GDI vehicles. In the present study we investigate one of the first mass production vehicles with GPF available in the European market. Regulated and non-regulated pollutants were measured over different test cycles and ambient temperatures (23 °C and −7 °C) in the laboratory and different on-road routes driven normally or dynamically and up to 1100 m altitude. The results showed that the vehicle respected all applicable limits. However, under certain conditions high emissions of some pollutants were measured (total hydrocarbons emissions at −7 °C, high CO during dynamic RDE tests and high NOx emissions in one dynamic RDE test). The particle number emissions, even including those below 23 nm, were lower than 6 × 1010 particles/km under all laboratory test cycles and on-road routes, which are <10% of the current laboratory limit (6 × 1011 particles/km).

Abatement potential analysis on CO2 and size-resolved particle emissions from a downsized LPG direct injection engine for passenger car

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.

Assessment of ethanol blended fuels for gasoline vehicles in China: Fuel economy, regulated gaseous pollutants and particulate matter

The government of China has announced an ambitious plan to expand the mandatory use of ethanol blended gasoline fuels by 2020. Given the dissimilarity in fuel properties between China and other countries with ethanol blending practices, it is necessary to assess the energy and environmental impacts of ethanol blending. In this study, we prepared two types of ethanol blended fuels (E10, with ethanol contents of approximately 10%) with lower contents of aromatics (ELA) and olefins (ELO), respectively, compared with the market China 5 gasoline. Nine in-use gasoline vehicles varying by manufacturer, engine technology, model year, and emission standard level were analyzed using a chassis dynamometer, which followed the Worldwide Harmonized Light Vehicles Test Cycle (WLTC). Two major positive effects from using E10 fuels could be observed in this study. First, tested turbocharged gasoline direct injection (GDI) vehicles could gain reductions in CO2 emission, fuel consumption and energy consumption by switching to the higher-octane-number ELO. This finding, along with the engine development trends in the automotive industry (e.g., downsizing and higher compression ratio), may have a synergistic effect to deliver greater energy efficiency in the future. Second, the two ethanol blended fuels could be more effective in reducing the particle mass (PM) and particle number (PN) emissions than the levels of using China 5 gasoline. Notably, the benefit of using ELO was more significant, with average emission reductions of 35% for the PM and of 44% for the PN. However, ELA and ELO possibly increased emissions of gaseous pollutants for certain vehicles in the study, but the intra-vehicle differences between the various fuel groups were not statistically significant (not significant, p > 0.05, t-test). We suggest that more measurements under various environmental conditions and comprehensive air quality simulations should be conducted to better understand the environmental impacts of ethanol blending in China.

European Regulatory Framework and Particulate Matter Emissions of Gasoline Light-Duty Vehicles: A Review

The particulate matter (PM) emissions of gasoline vehicles were much lower than those of diesel vehicles until the introduction of diesel particulate filters (DPFs) in the early 2000s. At the same time, gasoline direct injection (GDI) engines started to become popular in the market due to their improved efficiency over port fuel injection (PFI) ones. However, the PM mass and number emissions of GDI vehicles were higher than their PFI counterparts and diesel ones equipped with DPFs. Stringent PM mass levels and the introduction of particle number limits for GDI vehicles in the European Union (EU) resulted in significant PM reductions. The EU requirement to fulfill the proposed limits on the road resulted to the introduction of gasoline particulate filters (GPFs) in EU GDI models. This review summarizes the evolution of PM mass emissions from gasoline vehicles placed in the market from early 1990s until 2019 in different parts of the world. The analysis then extends to total and nonvolatile particle number emissions. Care is given to reveal the impact of ambient temperature on emission levels. The discussion tries to provide scientific input to the following policy-relevant questions. Whether particle number limits should be extended to gasoline PFI vehicles, whether the lower limit of 23 nm for particle number measurements should be decreased to 10 nm, and whether low ambient temperature tests for PM should be included.

Investigation on Blending Effects of Gasoline Fuel with N-Butanol, DMF, and Ethanol on the Fuel Consumption and Harmful Emissions in a GDI Vehicle

The effects of three kinds of oxygenated fuel blends—i.e., ethanol-gasoline, n-butanol-gasoline, and 2,5-dimethylfuran (DMF)-gasoline-on fuel consumption, emissions, and acceleration performance were investigated in a passenger car with a chassis dynamometer. The engine mounted in the vehicle was a four-cylinder, four-stroke, turbocharging gasoline direct injection (GDI) engine with a displacement of 1.395 L. The test fuels include ethanol-gasoline, n-butanol-gasoline, and DMF-gasoline with four blending ratios of 20%, 50%, 75%, and 100%, and pure gasoline was also tested for comparison. The original contribution of this article is to systemically study the steady-state, transient-state, cold-start, and acceleration performance of the tested fuels under a wide range of blending ratios, especially at high blending ratios. It provides new insight and knowledge of the emission alleviation technique in terms of tailoring the biofuels in GDI turbocharged engines. The results of our works showed that operation with ethanol–gasoline, n-butanol–gasoline, and DMF–gasoline at high blending ratios could be realized in the GDI vehicle without any modification to its engine and the control system at the steady state. At steady-state operation, as compared with pure gasoline, the results indicated that blending n-butanol could reduce CO2, CO, total hydrocarbon (THC), and NOX emissions, which were also decreased by employing a higher blending ratio of n-butanol. However, a high fraction of n-butanol increased the volumetric fuel consumption, and so did the DMF–gasoline and ethanol–gasoline blends. A large fraction of DMF reduced THC emissions, but increased CO2 and NOX emissions. Blending n-butanol can improve the equivalent fuel consumption. Moreover, the particle number (PN) emissions were significantly decreased when using the high blending ratios of the three kinds of oxygenated fuels. According to the results of the New European Drive Cycle (NEDC) cycle, blending 20% of n-butanol with gasoline decreased CO2 emissions by 5.7% compared with pure gasoline and simultaneously reduced CO, THC, NOX emissions, while blending ethanol only reduced NOX emissions. PN and particulate matter (PM) emissions decreased significantly in all stages of the NEDC cycle with the oxygenated fuel blends; the highest reduction ratio in PN was 72.87% upon blending 20% ethanol at the NEDC cycle. The high proportion of n-butanol and DMF improved the acceleration performance of the vehicle.

Impacts of gasoline aromatic and ethanol levels on the emissions from GDI vehicles: Part 1. Influence on regulated and gaseous toxic pollutants

Gasoline composition is critical to the formation of regulated emissions and gaseous toxic pollutants from spark ignition engines equipped with direct injection fueling. This study investigated the impacts of varying aromatic and ethanol levels on the exhaust emissions of five gasoline direct injection (GDI) vehicles. A total of eight fuels were used, with aromatic levels of 20% and 30% by volume, and ethanol levels ranging from 0% to 20% by volume. The test fleet consisted of 2016 to 2017 model year Tier 3 vehicles operated over the LA92 drive cycle. We showed that total aromatics played an important role for the emissions of non-methane hydrocarbons (NMHC), total hydrocarbons (THC), formaldehyde, and mono-aromatic hydrocarbon species (i.e., benzene, toluene, ethylbenzene, and xylenes), with an increase of gasoline aromatics resulting in higher emissions of these pollutants. Increasing ethanol levels in gasoline led to statistically significant reductions in carbon monoxide (CO) and statistically significant increases in acetaldehyde emissions. Emissions of nitrogen oxides (NOx) were not significantly affected by either aromatics or ethanol levels across the fleet. There was a lack of strong trends between the fuels in the ozone forming potential (OFP). The largest contribution to OFP in the exhaust was from aromatic species, followed by alkenes and alkanes. Overall, aromatics played a more dominant role in emissions formation than ethanol content, indicating multiple formation pathways for these pollutants.

Impacts of gasoline aromatic and ethanol levels on the emissions from GDI vehicles: Part 2. Influence on particulate matter, black carbon, and nanoparticle emissions

Fuel composition plays an important role on the particulate matter (PM) emissions formation from gasoline direct injection (GDI) engines. In this study, the impacts of gasoline chemical structure and physical properties on the particulate emissions were assessed for a fleet of five Tier 3 compliant GDI vehicles. All vehicles were tested on eight fuels with varying aromatic and ethanol levels, as well as varying PM indices (PMIs) over the LA92 test cycle in at least duplicate on each of the test fuels. Our results showed strong, statistically significant fuel differences for the weighted PM mass emissions and all three phases of the LA92 cycle. The higher aromatic content fuels showed increases in PM mass and black carbon emissions that were statistically significant compared to the lower aromatic fuels. The fuels with higher PMIs showed an upward, but not statistically significant, trend for PM mass emissions with increasing ethanol content likely due to ethanol’s evaporative charge cooling effect. This observation does not hold true for the lower PMI fuels. Similar trends to the weighted PM mass emissions were also seen for the cold-start and hot-running PM mass emissions, as well as for the weighted black carbon emissions, indicating a possible ethanol reinforcing effect on PM formation for the high PMI fuels. Total and solid particle number emissions also showed increases with the higher aromatic fuels compared to the lower aromatic fuels. Similar to PM mass, both total and solid particle number emissions demonstrated an upward trend for the high PMI fuels with an increase in ethanol content. While the study is consistent with other studies showing that increasing aromatics and PMI values lead to higher PM emissions, the results also suggest that this relationship is complicated by the presence of varying levels of ethanol in high aromatic and PMI fuels, where increasing levels of ethanol in these fuels can also lead to PM increases. High molecular weight and low volatility hydrocarbon species (especially aromatics) also strongly impacted particulate emissions formation in GDI vehicles.

Using a new Mobile Atmospheric Chamber (MACh) to investigate the formation of secondary aerosols from mobile sources: The case of gasoline direct injection vehicles

Direct primary emissions from light-duty passenger in the past 50 years have been reduced significantly. However, the potential of primary emissions to oxidize downwind of sources is challenging and not well understood. This study investigates the secondary aerosol (SA) forming potential of emissions generated from four wall-guided gasoline direct injection (GDI) vehicles operating under realistic driving conditions. The exhaust for each vehicle was collected in the new University of California, Riverside, Center for Environmental Research and Technology's (CE-CERT) Mobile Atmospheric Chamber (MACh) while driven over vehicle test cycles using a chassis dynamometer and subsequently, photochemically aged. Results show that the chemical and physical properties of the aged aerosol are significantly different between the GDI vehicles and consistent within each vehicle's chamber experiment. Ageing modifies the particle composition, density, volatility, and cloud condensation nuclei (CCN) hygroscopicity. Secondary aerosol studies from controlled-laboratory dynamometer and atmospheric chamber studies will provide additional insight into the environmental impact of real-world vehicular sources.

Comparison of regulated emission factors of Euro 6 LDV in Nordic temperatures and cold start conditions: Diesel- and gasoline direct-injection

Local air pollution in Norwegian wintertime is characterized by an increase in NO2 concentrations, due to poor dispersion and increased vehicle emissions. The focus of this study is therefore the characterisation of exhaust vehicle emissions in cold ambient temperatures. Euro 6 Gasoline Direct Injection (GDI) cars and diesel cars were tested in the laboratory in cold temperatures, including with cold start of the engine. Results show high emissions of CO2, PM and NOx. For the first time, we report also elevated NOx values for GDI vehicles. Further measurements are required to investigate whether these results are the beginning of a new trend of high NOx emissions from GDIs, or if these results represent singular events, but it may indicate that further NOx traps or catalysts are required for these vehicles. Understanding the relationship of cold ambient temperatures and vehicle emissions is also particularly important for air quality dispersion modelling, which do not currently account for emission temperature dependence.