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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 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.

Monodisperse and polydisperse Sodium Chloride (NaCl) particles were used to calibrate the solid particle penetration for the Volatile Particle Remover (VPR) in a Horiba prototype Solid Particle Counting System (SPCS). Prior to the calibration, dilution ratios on the SPCS are verified carefully with a flame ionization analyzer (FIA). Size distributions for polydisperse aerosols upstream and downstream of the Volatile Particle Remover (VPR) were measured with a Scanning Mobility Particle Sizer (SMPS). It is found that overall penetrations for polydisperse aerosols are larger than 95%. Geometric standard deviations from the raw and the diluted by the VPR are within ±1.5% difference. Thus, shapes of size distributions aren't changed after dilution. Geometric mean diameters shift a little, on average ±5% after dilution. Therefore, the VPR doesn't change the aerosol characteristics after the aerosol is diluted and heated up to 320 °C.

Solid particle emissions from a modern gasoline hybrid electrical vehicle (HEV) and a conventional gasoline vehicle were studied under diverse transient drive cycles on a chassis dynamometer. It is found that solid particle emissions from the conventional gasoline vehicle which has a 3.8-liter engine are sensitive to vehicle temperatures. Over 90% of solid particles are emitted during the first 250 seconds of transient cycles. Spikes for solid particle emissions from the HEV during a transient cycle are mainly caused by engine starts, hard accelerations after engine starts, and the engine running harder at high vehicle speeds. The engine and vehicle temperature status on the HEV doesn't show a strong correlation to the solid particle emission.

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.

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 Counting System (SPCS) has been developed according to the ECE draft regulation proposed by the particle measurement program (PMP). In the previous report the basic performance of the SPCS has been mentioned in detail [1, 2, 3, 4, 5 and 6]. It has been reported that the SPCS demonstrates very stable dilution of sample with air and the error of real time dilution factor is less than 6% up to the total dilution factor of 1000. Penetration of solid particles through the SPCS is over 95% and volatile particles removal efficiency is over 99%. In this study the SPCS has been used to investigate the soot emission behavior from different vehicles with different after-treatment technologies. Direct injection (DI) diesel vehicles without diesel particulate filter (DPF), and with different DPFs (catalyzed and non-catalyzed) have been tested. Direct injection gasoline (DIG) vehicle with oxidation and NOx reduction catalysts have also been tested.

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.

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.

An on-board diesel particulate measurement (OBS-TRPM) instrument is developed to measure on-road exhaust PM emission at Horiba. It is used to characterize particulate matter (PM) emission from a gasoline vehicle, the 1999 Ford Windstar with California Ultra Low Emission (ULEV) certification. PM emissions from three test cycles, EPA FTP 72, SFTP-US06, and new European drive cycle (NEDC), are evaluated. It is found that the PM emission from the SFTP-US06 with the cold start is roughly two times higher than PM emissions from the cold FTP 72 and the cold NEDC. This may be due to aggressive drive patterns for the US06 while the vehicle is still cold. The aggressive drive pattern for the US06 makes the gasoline vehicle emit a much higher fraction of elemental carbon (EC), and lower fraction of organic carbon (OC). Fractions of the EC from the vehicle are 9.1% for the FTP 72, 6.3% for the NEDC, and 56.6% for the US06.

The on-board transient response diesel particulate measurement (OBS-TRPM) instrument measures on-road vehicle particulate emissions. It is a continuation of the Horiba on-board PM sampler (OBS-PM) [5]. The OBS-TRPM measures total diesel particulate emission by collecting diesel particulate matter (PM) on a pre-weighed 47 mm filter while the partial flow sample system (OBS-PM) runs under a proportional control strategy. A real-time diffusion charge sensor (DCS) takes sample upstream of the filter, and measures diesel PM in term of particle length (mm/cm3). By integrating the DCS real-time signal during the filter sampling, the cumulative fraction of diesel PM emission is obtained. Finally, diesel PM mass emission during a specific region, for example a Not-to-Exceed (NTE) zone, is calculated from the fraction of the real-time PM signal. Thus, the OBS-TRPM provides a solution to measure PM emission in NTE zones which are defined by the US EPA.

On-board Particulate Matter (PM) mass calibration (OB-PMMC) is an approach to calibrate a real-time PM sensor with the gravimetric PM mass being collected on a conventional filter. The real-time PM sensor is integrated in a PM sample system and takes sample upstream of the sample filter. The PM mass collected on the filter is determined either by weighing the filter or by using analytical approaches. A unique calibration coefficient for each sample filter is generated for converting the PM real-time signal to the real-time PM mass emission. This calibration approach can be used to modify Constant Volume Samplers (CVS) and laboratory Partial Flow Sample Systems (PFSS), etc., into real-time PM mass measurement instruments for engine or vehicle exhaust PM measurement. The same technique may also be used to measure real-time PM concentration in the atmosphere under some circumstance.

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 family of cordierite DPF filters were developed and studied for their efficacy for catalyzed soot filter applications. In addition to porosity and median pore size of DPF filters, breadth of pore size distribution, microstructure, and pore connectivity have a profound influence not only in filter performance (pressure drop, catalyst coatability, and filtration efficiency) but also on mechanical and physical properties. Through filter material composition development, optimum values for the %porosity, median pore diameter, and breadth of the pore size distribution for minimizing pressure drop have been identified, leading to the development of a new family of high-porosity cordierite diesel particulate filters that possess a unique combination of high filtration efficiency, high strength, and very low clean and soot-loaded pressure drop in both the catalyzed and non-catalyzed states. By controlling the microstructure, the impact of the catalyst on pressure drop has been minimized.

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.

A single-stage dilution system has been designed to simulate the process of engine exhaust dilution in the atmosphere. An exhaust sample stream is introduced into a partial flow tunnel where it is diluted at a controlled rate. Temperature, relative humidity, dilution ratio and rate, and residence time are all adjustable. The system includes a turbulence generator to adjust the intensity of turbulence in the tunnel and a wake disk to control the initial mixing rate. Numerical methods were used to simulate flow fields, velocity fields, and mixing profiles for gases and particles. Mixing profiles for a gaseous tracer and particles of different sizes were also determined experimentally and compared with the model predictions. Critical parameters that influence mixing profiles and dilution rates predicted by modeling were demonstrated experimentally. Predicted and measured normalized mixing profiles were found to be in good agreement.