Gasoline Particulate Filters Research Articles

A multi-layer membrane filter made of potassium catalyst and three-way catalyst for a passive after-treatment system

A multi-layer membrane has been fabricated to integrate a Three-Way Catalyst (TWC) and Gasoline Particulate Filter (GPF) into one device, called a four-way catalytic converter. The top layer, made of nano-scale potassium catalyst particles, traps Particulate Matter (PM) with almost 100% filtration efficiency at all times and oxidizes PM (mostly soot) with a significantly reduced temperature of 476°C at the oxidation peak. Moreover, the bottom layer catalyst is comprised of sub-micro TWC particles to combine NO reduction and CO oxidation capabilities. The effective temperature range for the simultaneous removal of all pollutants was between 420°C–500°C.

Study on the Influence of the Cell Structure on the Pressure Drop of Gasoline Particulate Filter

The cell structure of a gasoline particulate filter (GPF) is made up of thousands of individual cells. Although the symmetric square cell structure of the GPF is commonly used internationally, several cell designs have been proposed to reduce the pressure drop in the GPF trapping process. The aim of this paper was to use AVL-Fire software to establish GPF models of different cell structures, mainly including the symmetric square cell structure, asymmetric square cell structure, and symmetric hexagonal cell structure, and analyze the GPF pressure drop characteristics of different cell structures according to the carrier structural parameters and altitude. The results show that compared with the pressure drop of the symmetric square cell structure, the pressure drop of the asymmetric cell structure with inlet/outlet side length ratios ranging from 1.1 to 1.4 is decreased by 4.61%, 9.07%, 12.19%, and 13.22%, respectively, and the pressure drop of the symmetric hexagonal cell structure is decreased by 33.17%. Both asymmetric and symmetric hexagonal cell structure GPFs can decrease the pressure drop during trapping by increasing the cell density. From 200 CPSI to 300 CPSI, the pressure drop of the asymmetric cell structure with inlet/outlet side length ratios ranging from 1.1 to 1.4 is decreased by 20.43%, 20.53%, 20.39%, and 18.56%, respectively, and the pressure drop of the symmetric hexagonal cell structure is decreased by 18.70%. The pressure drop values of GPFs with asymmetric and symmetric hexagonal cell structures show an increasing trend with an increasing filter wall thickness and inlet/outlet plug length. The pressure drop values of GPFs with asymmetric and symmetric hexagonal cell structures show an increasing trend with an increasing altitude, and the larger the inlet/outlet ratio, the more significant the increase in the pressure drop.

Towards zero pollution vehicles by advanced fuels and exhaust aftertreatment technologies

Vehicular emissions deteriorate air quality in urban areas notably. The aim of this study was to conduct an in-depth characterization of gaseous and particle emissions, and their potential to form secondary aerosol emissions, of the cars meeting the most recent emission Euro 6d standards, and to investigate the impact of fuel as well as engine and aftertreatment technologies on pollutants at warm and cold ambient temperatures. Studied vehicles were a diesel car with a diesel particulate filter (DPF), two gasoline cars (with and without a gasoline particulate filter (GPF)), and a car using compressed natural gas (CNG). The impact of fuel aromatic content was examined for the diesel car and the gasoline car without the GPF. The results showed that the utilization of exhaust particulate filter was important both in diesel and gasoline cars. The gasoline car without the GPF emitted relatively high concentrations of particles compared to the other technologies but the implementation of the GPF decreased particle emissions, and the potential to form secondary aerosols in atmospheric processes. The diesel car equipped with the DPF emitted low particle number concentrations except during the DPF regeneration events. Aromatic-free gasoline and diesel fuel efficiently reduced exhaust particles. Since the renewal of vehicle fleet is a relatively slow process, changing the fuel composition can be seen as a faster way to affect traffic emissions.

Multiscale simulation for sound transmission loss of a particulate filter in an exhaust system using a homogenization method

Most vehicles have diesel or gasoline particulate filters to remove particulate matter contained in gas from internal combustion engines. On the other hand, regulations have been in effect for vehicle-noise emission, with several studies conducted on reducing noise from the exhaust systems of automobiles. Generally, mufflers with expansion chambers and sound-absorbing materials have been used to reduce noise emissions; however, diesel or gasoline particulate filters have also been observed to reduce noise transmitted through the filter. Herein, a novel approach based on a microstructure model is proposed to predict the sound transmission loss through a diesel/gasoline particulate filter, the wall of which is made of a ceramic porous material. In this approach, a homogenization method for sound-absorbing poroelastic materials based on the asymptotic expansion approach is applied. The method was originally developed by one of the authors of this study. Microscopic structural images are obtained through μX-ray computed tomography, and a pore network model that consists of spherical pores and cylindrical throats is constructed to represent the characteristics of the porous filter wall. A microscopic unit cell model is derived from the expected values of the pore- and throat-size distributions obtained using the pore network model. Homogenized properties, such as permeability, equivalent density, and equivalent bulk modulus, are obtained through microscopic calculations using the unit cell model. Finally, the sound transmission loss is predicted through macroscopic calculations using the homogenized properties. The calculated sound transmission loss agreed well with the values measured using an acoustic tube and simplified exhaust systems.

GPF Filtration Characteristics Considering Fractal Characteristics of Particles and Filters

Abstract To reduce the emission of fine particulate matter (PM) from gasoline engines, a gasoline particulate filter (GPF) filtration model that considers the fractal characteristics of both particulate matter and filters is designed and its filtration characteristics are analyzed based on several GPF filtration models. Based on the GPF filtration mechanism, a new mathematical model of fiber efficiency filtration is established after correcting the classical filtration formula based on correcting the particle size of particles and considering the relationship between the porosity of the fiber filter and the fractal dimension of the filter. Simulation of the filtration efficiency of the established mathematical filtration model is carried out to obtain visual filtration efficiency curves. The filtration efficiency and pressure drop of the model are analyzed, and the effects of parameters such as particle fractal dimension, filter fractal dimension, filter thickness, flow rate, and fiber diameter on filtration efficiency are also comprehensively analyzed. The results show that when the fractal dimension of particles is in the range of 1.8-2.8, the most penetrating particle size decreases with the increase of the fractal dimension of particles. When the particle size is small, the effect of fractal dimension on filtration efficiency is not obvious. When the particle size is larger than the most penetrating particle range, the larger the fractal dimension, the filtration efficiency increases obviously. Considering the relationship between the fractal dimension of the filter body and the porosity and the influence of each on the filtration efficiency, the optimal fractal dimension of the filter body should be between 1.82 and 1.925, and the thickness of the filter has some influence on the filtration efficiency. The slower the gas flow rate is, the better the trapping effect will be. However, considering the problem of automobile emission, a lower exhaust speed can be chosen. Increasing the fiber diameter can improve the trapping efficiency of the model, but will reduce the porosity of the trapping collective. Therefore, the fiber diameter should not be too large under the combined action.

Molecular composition of fresh and aged aerosols from residential wood combustion and gasoline car with modern emission mitigation technology.

Emissions from road traffic and residential heating contribute to urban air pollution. Advances in emission reduction technologies may alter the composition of emissions and affect their fate during atmospheric processing. Here, emissions of a gasoline car and a wood stove, both equipped with modern emission mitigation technology, were photochemically aged in an oxidation flow reactor to the equivalent of one to five days of photochemical aging. Fresh and aged exhausts were analyzed by ultrahigh resolution mass spectrometry. The gasoline car equipped with a three-way catalyst and a gasoline particle filter emitted minor primary fine particulate matter (PM2.5), but aging led to formation of particulate low-volatile, oxygenated and highly nitrogen-containing compounds, formed from volatile organic compounds (VOCs) and gases incl. NOx, SO2, and NH3. Reduction of the particle concentration was also observed for the application of an electrostatic precipitator with residential wood combustion but with no significant effect on the chemical composition of PM2.5. Comparing the effect of short and medium photochemical exposures on PM2.5 of both emission sources indicates a similar trend for formation of new organic compounds with increased carbon oxidation state and nitrogen content. The overall bulk compositions of the studied emission exhausts became more similar by aging, with many newly formed elemental compositions being shared. However, the presence of particulate matter in wood combustion results in differences in the molecular properties of secondary particles, as some compounds were preserved during aging.

Combined Ash and Soot Monitoring for Gasoline Particulate Filters Using a Radio-Frequency-Based Sensor

Increasingly stringent emission limits have made particulate filters necessary for gasoline engines. Similar to diesel applications, gasoline particulate filters (GPFs) can be monitored by differential pressure measurement or by the radio-frequency-based filter diagnosis (RF sensor). In addition to measuring the soot loading, ash detection is critical for monitoring the GPF over the entire vehicle lifetime. Because the RF sensor detects the filter loading through a change in the dielectric properties of the GPF, it can detect not only soot but also ash. In diesel applications, the RF sensor has already demonstrated its potential for ash detection. To verify the feasibility of simultaneous ash and soot monitoring for GPFs, filters were loaded with ash on an engine test bench and measured on a lab test bench under defined synthetic exhaust gas conditions. By evaluating resonant modes, soot and ash could be clearly distinguished, as ash mainly affects the resonant frequency, while soot also changes the quality factor due to its high dielectric losses. However, higher soot loadings could not be detected by the resonant parameters, but instead by a frequency-averaged transmission signal. While the presence of ash caused an offset in this signal, its sensitivity to soot was not affected. Thus, the influence of ash can be corrected if the signal in the soot-free filter state is known, e.g., from the behavior of the resonant parameters. Therefore, even with a continuously increasing ash loading over the lifetime of a vehicle, an accurate soot detection is possible with the RF sensor.

Emission characteristics of intermediate volatility organic compounds from a Chinese gasoline engine under varied operating conditions: Influence of fuel, velocity, torque, rotational speed, and after-treatment device

Improved measurement of new pollutants, particularly intermediate volatility organic compounds (IVOCs), is urgently needed due to the lack of emission data under various operating conditions and potential fuel switching for gasoline engines. This study focused on examining the emission characteristics of IVOCs and the formation of secondary organic aerosols (SOA) in a commercial gasoline direct injection (GDI) engine, considering different fuels and operating conditions. The key findings are as follows: (1) The emission factor (EF) of IVOCs ranged from 2.0 to 357.8 mg kg-fuel−1, with a median value of 87.9 mg kg-fuel−1. (2) IVOCs emission characteristics were influenced by the fuel type and engine operating conditions. The addition of ethanol resulted in a significant decrease in IVOCs emissions, while lower velocities and torques led to higher IVOCs emissions. (3) Ethanol-blended fuel scenarios (E10, E25) and CGPF (Pd/Rh catalytically coated gasoline particle filter)-equipped scenarios exhibited high proportions of oxygen-containing compounds like aliphatic alcohols, ethers, and carboxylic acids. (4) IVOCs exhibited a high potential for the formation of SOA, underscoring the importance of controlling IVOCs in future strategies to mitigate particulate matter pollution in China. These findings highlight the significance of smooth traffic flow and advancements in fuel types, engine technologies, and after-treatment designs to effectively control IVOC emissions and contribute to the realization of a carbon-neutral society.

Effect of dopants on soot oxidation over doped Ag/ZrO2 catalysts for catalyzed gasoline particulate filter

Soot oxidation was studied using silver-zirconia catalysts doped with Y, La, Ce and Pr under a low concentration of O2, typical for gasoline direct injection engine conditions, in view of practical gasoline particulate filter application. The Ag/La-ZrO2 catalyst revealed the best catalyst performance for soot oxidation exhibiting a Tmax of 405 °C for a fresh sample and 420 °C after aging at 700 °C for 6 h. Additionally, the doped catalysts exhibited improved activity for co-oxidation of CO and C3H6. The Ag/ZrO2 catalyst benefited from doping via the synergy between silver particles and doped zirconia.

Effects analysis on hydrocarbon removal performance of an adsorptive catalytic gasoline particulate filter in the gasoline engine during cold start

In order to remove hydrocarbon (HC) emission of the gasoline engine during cold start to meet increasingly stringent emission standards, the HC removal performance of a novel adsorptive catalytic gasoline particulate filter (A-CGPF) coated with new composite catalysts is investigated. Then, effects of different factors on HC removal (HC adsorption and conversion) of the A-CGPF during cold start are analyzed. The results show that during first 40 s of the cold start, the cumulative emission of hydrocarbon is greatly reduced. Ambient temperature has a great influence on hydrocarbon removal in the early stage of cold start, and its variation has little effect on MMC. The order of hydrocarbon removal performance during cold start under non-adiabatic condition is MRP > MMC > MP > MC > MPCZ, and the difference of hydrocarbon removal rate between MMC and MRP is only 5%–9%. In addition, the larger ratio of oxidizing components and reductive components λ can lead to the faster temperature rise and the greater hydrocarbon removal rate. The λ value has little influence on the early stage of cold start, but gradually increases the influence on the late stage of that until it is up to 0.95. During soot capture, the ash accumulation has a more significant effect on HC abatement at the late stage of cold start, which can delay the temperature rise in the filter and slightly decrease the hydrocarbon removal rate. This work provides reference for enhancing simultaneous hydrocarbon and soot reduction performance of the A-CGPF under the low temperature and design of coupled after-treatment system.

Particulate emissions from gasoline vehicles using three different fuel injection technologies

Gasoline vehicle emission is a major source of urban particulate matter (PM), particularly ultra-fine PM (≤100 nm), exerting adverse health effects. While the PM emissions from port fuel injection (PFI) and gasoline direct injection (GDI) vehicles have been well addressed in previous studies, few studies have reported the PM emission from the new mixed injection (MI) vehicles. Here, we employed a chassis dynamometer to investigate particle emissions under the Worldwide Harmonized Light vehicles Test Cycles (WLTC) from vehicles with three different fuel injection technologies. The PM and particle number (PN) emission factors (EFs) for MI vehicles are 129.53 μg/km and 1.0 × 1013 #/km, respectively. A trend of PFI > MI > GDI is observed for both PM and PN EFs for vehicles with same emission standard. Notably, the PM emissions of MI vehicles are greatly affected by both fuel injection methods at low and medium speeds, but are more significantly affected by PFI at high speeds. MI vehicle shows much lower PM and PN emissions than other vehicles at low-, medium-, and high-speed phases, but substantial hiher ultra-fine PM emission at extra-high speed phase. This is because the insufficient air supplied by naturally-aspirated engine of MI vehicles in the high-load region leads to incomplete combustion and generate large formation of ultra-fine particles. Besides, the gasoline particulate filter reduces 94.5% of PM emission but produces abundant nucleation-mode particles during regeneration at the extra-high speed phase for MI vehicles. Our study gives an insight to the state-of-the-art engine technology, i.e., MI vehicles, and reveals that this new technology is a feasible alternative for simultaneously reducing pollutant emissions from gasoline vehicles.

Proposal for New Development Environment Based on Digital Materials and a Case Study of Gasoline Particulate Filter

Carbon dioxide emissions must be reduced as a countermeasure against global warming. A gasoline direct injection (GDI) engine is known for its high fuel economy, but there are more particulate emissions. To trap these particulates, a gasoline particulate filter (GPF) is needed. In this study, numerical simulations of the flow field in the GPF have been performed using the lattice Boltzmann method (LBM). Three types of filters were tested by our proposed approach, named as a digital material technique, where virtual materials are created by the simulation. Focusing on the pore characteristics of the filters, we used filters with the same pore size but different porosity. For comparison, the real internal structures of the actual GPF were detected using an X-ray CT method. The simulated flow field and the pressure drop across the filter wall were investigated, comparing with those of the actual GPF. As a result, it was found that the larger the porosity, the smaller the pressure drop. By setting the pore size and porosity to the same values as the actual GPF, a similar flow field was obtained, and the value of the pressure drop was close to that of the actual GPF.

Effects of a gasoline particulate filter on the physicochemical characteristics of particulate matter from a gasoline engine

Gasoline particulate filters (GPFs) are being used increasingly in gasoline direct-injection engines because they can reduce particle emissions and allow emission regulations to be met. Therefore, understanding the particles' physicochemical properties can help with optimizing the post-processing systems and engine calibration. In this study, particles were collected both pre- and post-GPF using a Dekati® low-pressure impactor and a quartz-fiber filter membrane. High-resolution transmission electron microscopy was used to observe the morphologies of the particles, the fractal dimension was used to quantify the aggregate structure, and an image-processing program developed in MATLAB was used to analyze the nanostructures of the primary particles. Raman spectroscopy was used to study the order degree of the particles’ carbon crystal arrangement, and Fourier transform infrared spectroscopy was used to assess the changes in their surface functional-group content. After the particles were graded according to particle size, it was found that (i) the fractal dimension of all size levels and (ii) the average size of the primary particles were both smaller post-GPF than pre-GPF. Post-GPF, there was a higher proportion of nucleated particles, the particle fringe length was shorter, the tortuosity and separation were both greater, the particles were more disordered, the ratio of C–H to C–O was greater, and the proportion of organic composition of the particles and their oxidation activity were both increased.

Investigation of Lubricant Additive Interactions on Gasoline Particulate Filters

<div>To understand how the composition of novel lubricant additives and their ash interact with gasoline particulate filters (GPFs), an accelerated aging protocol was conducted using three lubricant additive formulations and two GPF types. The additive packages (adpaks) consisted of Ca+Mg detergent in a 3:1 or 0:1 ratio and an anti-wear component—either zinc dialkyl dithiophosphate (ZDDP) or a novel phosphonium-phosphinate ionic liquid (IL) substitute. The particulate sampling captured amount/compositions of particulate matter (PM) generated, total particulate number, and size distribution. Five ash loadings were completed. GPF position and adpak composition affected the backpressure, ash composition, ash morphology, and captured mass. The particulate sampling indicated that the ash component consisted primarily of particles less than 50 nm in size and that the Mg-only adpak resulted in more particulate of 50–400 nm in size. Postmortem materials characterization indicated GPFs in the underfloor position had deeper penetration of ash into the walls compared to the close-coupled position. Additionally, the Mg-only adpak had a higher filter collection efficiency (>90%) and the ash particles consisted of a higher concentration of dense ash material. In contrast, four of the 3:1 Ca:Mg lubricant adpaks resulted in a collection efficiency of only 40–50%. Although the collection efficiency was higher with the Mg-only adpak, the ash layer in the GPF was not thicker, nor was the penetration into the wall more significant, and surprisingly the full useful life (FUL) backpressure was lower than with Ca:Mg adpaks. The higher density of the Mg-derived ash was the only detectable difference. A possible explanation of this observation is that Mg ash has a lower melting point and is more susceptible to densification during combustion or GPF regeneration. The substitution of IL in place of the ZDDP did not lead to any notable changes in collection efficiency or location of the ash.</div>

A dual-geometry pore-size-resolved model to predict deep-bed loading in a wall-flow filter

A gasoline particulate filter (GPF) is an effective wall-flow technology for gasoline engine particulate matter (PM) emission control via deep-bed filtration through porous ceramic walls within a honeycomb channel structure. An analytical filter model is desired to understand its efficiency and pressure drop under engine operating conditions and, thereby, reduce the development costs for meeting emission regulations and engine performance targets. Most existing models either oversimplify the filter geometry or do not offer good predictions in the soot loading regime. The present work treats the deep bed regime as two co-existing filters with different geometries based on their natural morphologies, one that describes the porous wall and the other for the fiber structure created by soot deposition. Both models are dynamic to account for changes in pore size distribution and soot dendrite growth during loading. Model validation by 12 sets of experimental filter loading data shows that it provides reasonable predictions of both filter efficiency and pressure drop during deep-bed loading for different GPF wall-flow filters under various operating conditions. Scanning electron microscopy (SEM) confirms model predictions for the unit collector size of the dendritic filter formed by soot deposition. Numerical simulation using GeoDict was also carried out to validate the model predictions on particle deposition location. The model is used to investigate the evolution of pore-size-resolved aerosol flow, filtration efficiency, mass loading, and particle packing density during loading. The impact of porosity, mean pore size, and pore size distribution on filter loading performance is studied. The results suggest that increasing porosity, narrowing pore size distribution, and increasing mean pore size can improve filter performance, offering pathways for future filter optimization.

Low-content and highly effective zoned Rh and Pd three-way catalysts for gasoline particulate filter potentially meeting Euro 7

The next-generation Euro 7 standard proposed much lower pollutant limits from gasoline vehicles, specifically for CO and NOx, which would be challenging for the three-way catalysts (TWCs) utilized commercially to eliminate these pollutants. TWCs with reductive (Rh) and oxidative (Pd) active components on gasoline particulate filters (TWC on GPF) play importantly auxiliary roles in the remediation of CO and NOx downstream the close coupled TWCs to meet their emission targets. Here, a low-content Rh-based TWC (0.17 wt%) zoned with a less expensive Pd-based TWC (0.29 wt%) for GPF applications (cGPF) is reported using improved colloidal deposition method. The supporting of Rh on Y-stabilized ZrO2 rather than on CeO2–ZrO2 inhibits the formation of inactive Ce rhodate species, while Pd on CeO2–ZrO2 not only guarantees the high oxygen storage capacity (OSC) but also enhances catalytic activity. The layout of the front one-fifth in volume being 0.29 wt% Pd on Ce0.43Zr0.57O2 and the rear four-fifths being 0.17 wt% Rh on Zr0.85Y0.15O2 prevents the possible alloying of Rh with Pd. The highly effective zoned Rh and Pd TWCs show synergistic three-way activity before and after severe hydrothermal aging at 1000 °C with 10% water for 24 h, which could be potential choices for close coupled GPF application to satisfy the upcoming stringent emission standards, such as Euro 7 and China 6b.

Characterization of Soot Loading and Filtration Efficiency of a Gasoline Particulate Filter with Photoacoustic Sensor and Particle Number Counting Systems

An optimum operation of a gasoline particulate filter (GPF) for a gasoline direct injection vehicle in terms of its performance of pressure drop, soot loading, and filtration efficiency becomes inevitable to fulfill upcoming emission regulations. This paper proposes a methodology to characterize the GPF performance for validation of simulation models for more precise operation strategies along with future legislative requirements. The feasibility was examined through experiments of miniature GPF samples using a synthetic particle generator. Firstly, permeability of the GPF walls was estimated to be 6.9 ± 1.5 × 10−13 m2 by a flow resistance descriptor model, which was in good agreement with its pore structure. Secondly, photoacoustic sensor systems indicated soot accumulation inside the GPFs in real time thanks to linear correlations between sensor signals and soot mass concentrations in exhaust. Thirdly, particle number counting systems compliant with respective regulatory technical requirements exhibited time-resolved filtration efficiencies of the GPFs in conjunction with solid particle number emissions whose diameter was larger than 10 nm and 23 nm. The filtration efficiencies at a clean state of the GPF were 0.78 and 0.77, respectively. The slight difference could be explained by Brownian diffusion and interception for particle filtration.

Impacts on real-world extra cold start emissions: Fuel injection, powertrain, aftertreatment and ambient temperature

Vehicles emit substantial amounts of pollutants during start periods. Engine starts mainly occur in urban areas, causing serious harm to humans. To investigate the impacts on extra cold start emissions (ECSEs), eleven China 6 vehicles with various control technologies (fuel injection, powertrain, and aftertreatment) were monitored with a portable emission measurement system (PEMS) at different temperatures. For conventional internal combustion engine vehicles (ICEVs), the average ECSEs of CO2 increased by 24%, while the average ECSEs of NOx and particle number (PN) decreased by 38% and 39%, respectively, with air conditioning (AC) on. Gasoline direct injection (GDI) vehicles had 5% lower CO2 ECSEs, but 261% higher NOx ECSEs and 318% higher PN ECSEs than port fuel injection (PFI) vehicles at 23 °C. The average PN ECSEs were significantly reduced by gasoline particle filters (GPFs). The GPF filtration efficiency was higher in GDI than PFI vehicles due to particle size distribution. Hybrid electric vehicles (HEVs) generated excessive PN extra start emissions (ESEs), resulting in a 518% increase compared to ICEVs. The start times of the GDI-engine HEV accounted for 11% of the whole test time, but the proportion of PN ESEs relative to total emissions were 23%. Linear simulation based on the decrease in ECSEs with increasing temperature underestimated the PN ECSEs from PFI and GDI vehicles by 39% and 21%, respectively. For ICEVs, CO ECSEs varied with temperature in a U shape with a minimum at 27 °C; NOx ECSEs decreased as ambient temperature increased; PFI vehicles generated more PN ECSEs at 32 °C than GDI vehicles, stressing the significance of ECSEs at high temperature. These results are useful for improving emission models and assessing air pollution exposure in urban aeras.

Characterization of a Lightly Loaded Underfloor Catalyzed Gasoline Particulate Filter in a Turbocharged Light Duty Truck.

A test program to characterize the benefits and challenges of applying a European series production catalyzed gasoline particulate filter (GPF) to a U.S. Tier 2 turbocharged light duty truck (3.5L Ecoboost Ford F150) in the underfloor location was initiated at the U.S. Environmental Protection Agency. The turbos and underfloor location keep the GPF relatively cool and minimize passive regeneration relative to other configurations. This study characterizes the relatively cool GPF in a lightly loaded state, approximately 0.1 to 0.4 g/L of soot loading, using four test cycles: 60 mph steady state, 4-phase FTP, HWFET, and US06. Measurements include GPF temperature, soot loading, GPF pressure drop, brake thermal efficiency (BTE), CO2, PM mass, elemental carbon (EC), filter-collected organic carbon (OC), CO, THC, and NOx emissions. The lightly loaded underfloor GPF achieves 85-99% reduction in PM mass, 98.5-100.0% reduction in EC, and 65-91% reduction in filter-collected OC, depending on test cycle. The smallest reductions in PM and EC occur in the US06 cycle due to mild GPF regeneration caused by GPF inlet temperature exceeding 500°C. EC dominates filter-collected OC without a GPF, while OC dominates EC with a GPF. Composite cycle CO, THC, and NOx emissions are reduced by the washcoat on the GPF but the low temperature location of the GPF does not make best use of the catalyzed washcoat. Cycle average pressure drop across the GPF ranged from 1.25 kPa in the 4-phase FTP to 4.64 kPa in the US06 but did not affect BTE or CO2 emissions in a measurable way in any test cycle.

Combustion and emissions characteristics of methanol/gasoline CISI engines under different injection modes

Methanol was a promising alternative fuel for spark ignition engines due to its liquid nature, large octane number and high oxygen content. The combined injection technology had the advantages of greater control flexibility, less engine knock tendency, and less engine-out emissions. However, the preferable injection mode of methanol/gasoline dual fuel engine was rarely reported. In this study, the combustion and emission characteristics of methanol/gasoline dual fuel engine with different injection modes, methanol direct injection plus gasoline port injection (MDI + GPI) or gasoline direct injection plus methanol port injection (GDI + MPI), were studied experimentally. The results showed that MDI + GPI mode was preferred for methanol/gasoline dual fuel engines, as this mode yielded higher engine brake effective mean pressure, larger heat release rate, lower cyclic variation, and less particle number emissions. An unimodal nucleation pattern particle size distribution can be observed for the MDI + GPI mode, which was beneficial for the after-treatment of particles in gasoline particle filter.