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Four-way, integrated, diesel emission control systems that combine selective catalytic reduction for NOx control with a continuously regenerating trap to remove diesel particulate matter were evaluated under real-world, on-road conditions. Tests were conducted using a semi-tractor with an emissions year 2000, 6-cylinder, 12 L, Volvo engine rated at 287 kW at 1800 rpm and 1964 N-m. The emission control system was certified for retrofit application on-highway trucks, model years 1994 through 2002, with 4-stroke, 186-373 kW (250-500 hp) heavy-duty diesel engines without exhaust gas recirculation. The evaluations were unique because the mobile laboratory platform enabled evaluation under real-world exhaust plume dilution conditions as opposed to laboratory dilution conditions. Real-time plume measurements for NOx, particle number concentration and size distribution were made and emission control performance was evaluated on-road.

A dilute spark-ignited engine concept has been developed as a potential low cost competitor to diesel engines by Southwest Research Institute (SwRI), with a goal of diesel-like efficiency and torque for light- and medium-duty applications and low-cost aftertreatment. The targeted aftertreatment method is a traditional three-way catalyst, which offers both an efficiency and cost advantage over typical diesel aftertreatment systems. High levels of exhaust gas recirculation (EGR) have been realized using advanced ignition systems and improved combustion, with significant improvements in emissions, efficiency, and torque resulting from using high levels of EGR. The primary motivation for this work was to understand the impact high levels of EGR would have on particulate matter (PM) formation in a port fuel injected (PFI) engine. While there are no proposed regulations for PFI engine PM levels, the potential exists for future regulations, both on a size and mass basis.

Human exposure to vehicle exhaust during engine start-up can be encountered on a daily basis in parking lots, home garages, and vehicle stop/star traffic environment. This work is the first pilot study to characterize solid particle number and size distribution during engine start-up using various light-duty vehicles with different technology engines. A total of 84 vehicles were tested in this pilot study, consisting of post-2007 diesel engines equipped with high efficiency diesel particulate filters (DPFs) as well as modern gasoline port fuel injected (PFI) and gasoline direct injected (GDI) engines equipped with three-way-catalysts (TWCs). Particle concentration from DPF equipped diesel engines were found to be the lowest, while GDI and 8-cylinder PFI engines had the highest particle emissions.

A 1.9 liter Volkswagen TDI engine has been modified to accomodate the addition of hydrogen into the intake manifold via timed port fuel injection. Engine out particulate matter and the emissions of oxides of nitrogen were investigated. Two fuels,low sulfur diesel fuel (BP50) and soy methyl ester (SME) biodiesel (B99), were tested with supplemental hydrogen fueling. Three test conditions were selected to represent a range of engine operating modes. The tests were executed at 20, 40, and 60 % rated load with a constant engine speed o 1700 RPM. At each test condition the percentage of power from hydrogen energy was varied from 0 to 40 %. This corresponds to hydrogen flow rates ranging from 7 to 85 liters per minute. Particulate matter (PM) emissions were measured using a scaning mobility particle sizer (SMPS) and a two stage micro dilution system. Oxides of nitrogen were also monitored.

A solid particle number measurement system (SPNMS) was developed using a catalytic stripper (CS) technology instead of an evaporation tube (ET). The ET is used in commercially available systems, compliant with the Particle Measurement Program (PMP) protocol developed for European Union (EU) solid particle number regulations. The catalytic stripper consists of a small core of a diesel exhaust oxidation catalyst. The SPNMS/CS met all performance requirements under the PMP protocol. It showed a much better performance in removing large volatile tetracontane particles down to a size well below the PMP lower cut-size of 23 nm, compared to a SPNMS equipped with an ET instead of a CS. The SPNMS/CS also showed a similar performance to a commercially available system when used on a gasoline direct injection (GDI) engine exhaust.

Gasoline direct injected (GDI) engines are becoming a concern with respect to particulate matter (PM) emissions. The upcoming 2014 Euro 6 regulations may require a drastic reduction in solid particle number emissions from GDI engines and the proposed California Air Resources Board (CARB) LEV III regulations for 2014 and 2017 will also require some PM reduction measures. As a result, it is necessary to characterize PM emissions from GDI engines and investigate strategies that suppress particle formation during combustion. The main focus of this work was on using exhaust gas recirculation (EGR) as a means to reduce engine-out particle emissions from a GDI engine with an overall stoichiometric fuel to air mixture. A small displacement, turbocharged GDI engine was operated at a variety of steady-state conditions with differing levels of EGR to characterize total (solid plus volatile) and solid particle emissions with respect to size, number, and soot or black carbon mass.

This paper summarizes the Heavy-Duty In-Use Testing (HDUIT) measurement allowance program for Particulate Matter Portable Emissions Measurement Systems (PM-PEMS). The measurement allowance program was designed to determine the incremental error between PM measurements using the laboratory constant volume sampler (CVS) filter method and in-use testing with a PEMS. Two independent PM-PEMS that included the Sensors Portable Particulate Measuring Device (PPMD) and the Horiba Transient Particulate Matter (TRPM) were used in this program. An additional instrument that included the AVL Micro Soot Sensor (MSS) was used in conjunction with the Sensors PPMD to be considered a PM-PEMS. A series of steady state and transient tests were performed in a 40 CFR Part 1065 compliant engine dynamometer test cell using a 2007 on-highway heavy-duty diesel engine to quantify the accuracy and precision of the PEMS in comparison with the CVS filter-based method.

The use of a corona-less electrostatic precipitator as a collection and agglomeration device for diesel soot has been investigated. It collects and grows diesel particles which are emitted in the submicron diameter range and grow into much larger particles. These larger particles may then be collected with a relatively simple inertial device. Previous testing of a full scale precipitator designed for a Caterpillar 3304 engine showed that the reduction in sub-micron sized mass from the engine was roughly 30 to 40%. Greater reductions were desired. A sub-scale electrostatic agglomerator was built to analyze in greater detail the behavior of an existing full scale device. Tests were designed to determine; the charged fraction of the particles from the engine used, the collection efficiency of the electrostatic agglomerator, the effect of geometry on collection efficiency, and the size distribution of the particles reentrained after electrostatic collection.

A study of the sources of variability in particulate measurements using the Heavy-Duty Transient Test (40 CFR Subpart N) has been conducted. It consisted of several phases: a critical examination of the test procedures, visits to representative facilities to compare and contrast facility designs and test procedures, and development of a simplified model of the systems and procedures used for the Heavy-Duty Transient Test. Some of the sources of variability include; thermophoretic deposition of particulate matter onto walls of the sampling system followed by subsequent reentrainment in an unpredictable manner, the influence of dilution and cooling upon the soluble organic fraction, inconsistency among laboratories in the engine and dynamometer control strategies, and errors in measurements of flows into and out of the secondary dilution tunnel.

Soot is the largest component of contaminants found in the diesel engine lubricating oil. The soot enters lubricating oil mainly through thermophoretic deposition on the cylinder wall. Although the mechanism is still not fully understood, it is generally accepted that soot particles promote engine wear, reducing engine component service life, fuel efficiency and performance. This problem will be further exacerbated when more and more diesel engines use EGR to reduce NOx emissions and when lubricating oil consumption is drastically reduced to control particulate emissions. In this study, lubricating oil samples were taken from 7 different operating diesel engines. The size distribution and concentration of the diesel soot particles in the lubricants were investigated by methods of photosedimentation and quantitative spectrophotometry. The size distributions were compared to those of soot particles in the exhaust.

Total and solid particle mass, size, and number were measured in the dilute exhaust of a 2009 vehicle equipped with a gasoline direct injection engine along with an exhaust three-way-catalyst. The measurements were performed over the FTP-75 and the US06 drive cycles using three different U.S. commercially available fuels, Fuels A, B, and C, where Fuel B was the most volatile and Fuel C was the least volatile with higher fractions of low vapor pressure hydrocarbons (C10 to C12), compared to the other two fuels. Substantial differences in particle mass and number emission levels were observed among the different fuels tested. The more volatile gasoline fuel, Fuel B, resulted in the lowest total (solid plus volatile) and solid particle mass and number emissions. This fuel resulted in a 62 percent reduction in solid particle number and an 88 percent reduction in soot mass during the highest emitting cold-start phase, Phasel, of the FTP-75, compared to Fuel C.

A major problem with many soot emission control devices is the fact that they quickly become loaded with soot which must be removed by a controlled burning (regeneration) process. The need for regeneration greatly complicates such diesel particle emission control devices. In this paper, an electrostatic agglomerator (ESA) which efficiently collects diesel particles but does not require regeneration is described. The ESA is an electrostatic precipitator which is designed to collect and subsequently reentrain diesel soot particles. The collection and reentrainment processes results in growth of particle diameter from roughly 0.2 μm to larger than 1.0 μm. The agglomerated particles are large enough to be collected by a relatively simple inertial device, e.g., a cyclone separator. The collected particle may be either recycled to the engine or disposed of by other means. Electrostatic collection is made easier by the fact that diesel particles are charged by the combustion process itself.

There is a growing body of evidence that in-cylinder surfaces play an important role in determining the nature and quantity of soot emitted by diesel engines. This paper describes recent experimental results which demonstrate the importance of both the deposition of soot on walls during the combustion process and its subsequent reentrainment during exhaust blowdown. Soot deposition was demonstrated both experimentally and theoretically. The principal mechanism of soot deposition during combustion is thermophoresis. Our results suggest that the gross rate of in-cylinder deposition in the indirect injection diesel engine is between 20 and 45 percent of the net soot emission rate. Thus, a significant fraction of the soot emitted may have been stored on combustion chamber surfaces and protected from oxidation. Further evidence of wall deposition and subsequent reentrainment has been obtained by making time-resolved measurements of soot concentrations in the exhaust.

A solid particle sampling system (SPSS) that is equipped with a heated oxidation catalyst, micro-dilution tunnels, filter holders and sampling probes, was designed and developed to collect filter-based solid and total (solid plus volatile) particles from the exhaust of internal combustion engines, and to facilitate the measurement of solid and total particles when equipped with particle measuring instruments for size, number, mass, and other particle characteristics. The SPSS was characterized with laboratory aerosol and showed a very low solid particle loss of less than 5 percent using sodium chloride particles, very high volatile particle removal of better than 98 percent using oil droplets, and no formation of sulfuric acid particles when using ammonium sulfate particles. The SPSS is a useful tool for researchers interested in characterizing the solid and volatile fraction of particles emitted from combustion sources.

The effects of fuel sulfur content and dilution conditions on diesel engine PM number emissions have been researched extensively through steady state testing. Most results show that the concentration of nuclei-mode particles emitted increases with fuel sulfur content. A few studies further observed that fuel sulfur content has little effect on the emissions of heavily-used engines. It has also been found that primary dilution conditions can have a large impact on the size and number distribution of the nuclei-mode particles. These effects, however, have not yet been fully understood through transient testing, the method used by governments worldwide to certify engines and regulate emissions, and a means of experimentation which generates realistic conditions of on-road vehicles by varying the load and speed of the engine.

Horiba on-board diesel exhaust particulate sampler (OBS-PM) is a filter based partial flow particulate sampling system used for On-board diesel particulate matter (PM) measurement. It takes sample from either raw or diluted exhaust. It can run at constant dilution ratios or at variable dilution ratios with proportional control on the sample flow. The diluted exhaust moves through a pre-weighed 47 mm particulate filter and PM is collected on the filter. By weighing the loaded sample filter, PM emission from the engine or the vehicle can be determined. The performance of the OBS-PM meets most of requirements for a real-time partial flow sample system (PFSS) recommended by ISO 16183 [2]. The physical size and the power consumption of the instrument are minimized. It is powered with four 12 volts batteries, and can be installed on a vehicle for real-world PM emission evaluation.

In 2005, the United States Environmental Protection Agency (EPA) and Southwest Research Institute (SwRI) embarked on a mission to help the city of Beijing, China, clean its air. Working with the Beijing Environmental Protection Bureau (BEPB), the effort was a pilot diesel retrofit demonstration program involving three basic retrofit technologies to reduce particulate matter (PM). The three basic technologies were the diesel oxidation catalyst (DOC), the flowthrough diesel particulate filter (FT-DPF), and the wallflow diesel particulate filter (WF-DPF). The specific retrofit systems selected for the project were verified through the California Air Resources Board (CARB) or the EPA verification protocol [1]. These technologies are generally verified for PM reductions of 20-40 percent for DOCs, 40-50 percent for the FT-DPF, and 85 percent or more for the high efficiency WF-DPF.

Particle concentrations and size distributions were measured in the exhaust of a turbocharged, aftercooled, direct-injection, Diesel engine equipped with a ceramic filter (trap). Measurements were performed both upstream and downstream of the filter using a two-stage, variable residence time, micro-dilution system, a condensation particle counter and a scanning mobility particle sizer set up to count and size particles in the 7-320 nm diameter range. Engine operating conditions of the ISO 11 Mode test were used. The engine out (upstream of filter) size distribution has a bimodal, log normal structure, consisting of a nuclei mode with a geometric number mean diameter, DGN, in the 10-30 nm range and an accumulation mode with DGN in the 50-80 nm range. The modal structure of the size distribution is less distinct downstream of the filter. Nearly all the particle number emissions come from the nuclei mode, are nanoparticles (Dp < 50nm), and are volatile.

Earlier work [1] shows that kinetics of Diesel soot oxidation is different from that of ethylene diffusion flame soot oxidation [2], possibly due to metals from lube oil. This study investigates the influence of metals on soot oxidation and the exhaust particle emissions using lube oil dosed fuel (2 % by volume). This method does not simulate normal lube oil consumption, but is used as a means of adding metals to particles for oxidation studies. This study also provides insight into the effect of systems that mix lube oil with fuel to minimize oil change service. The HTO-TDMA (High Temperature Oxidation-Tandem Differential Mobility Analyzer) technique [1] was used to measure the surface specific oxidation rate of Diesel particles over the temperature range 500-750 °C. Diesel particles sampled from the exhaust stream of a Diesel engine were size segregated by differential mobility and oxidized in situ in air in a heated flow tube of known residence time and temperature profile.

A one-stage dilution tunnel has been developed to sample and dilute diesel exhaust. The tunnel has the capability of simulating many aspects of the atmospheric dilution process. The dilution rate and overall dilution ratio, temperature, relative humidity, and residence time in the tunnel, as well as residence time and temperature in the transfer line between the tunnel and exhaust sampling point may be varied. In this work we studied the influence of the exhaust transfer line, tunnel residence time, and dilution air temperature on the exhaust particle size distribution. The influences of fuel sulfur content on the size distribution and on the sensitivity of the size distribution to dilution and sampling conditions were also examined. We do not suggest an optimum dilution scheme, but do identify critical variables.