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Three light-duty vehicles in five different configurations [a Honda Accord operating with diesel with a closed-coupled oxidation catalyst and an underfloor catalyst replaced in some tests with a diesel particle filter (DPF), a Toyota Corolla operating with gasoline, and a VW Golf alternatively operating with petrodiesel or biodiesel] were tested in a dynamometer facility to develop an improved understanding of the factors affecting the toxicity of particulate exhaust emissions. The vehicles were tested using a variety of real-world driving cycles, more than the certification test (New European Driving Cycle). Particle samples were collected and analyzed for elemental and organic carbon (EC and OC, respectively), water soluble and water insoluble organic carbon (WSOC and WISOC, respectively), and inorganic ions, and the emission rates (mg/km) for each vehicle/configuration were determined. A dithiothreitol (DTT) assay was used to assess the oxidative potential of the particulate matter (PM) samples. The DPF-equipped diesel and gasoline vehicles were characterized by the lowest overall PM mass emissions, while the diesel and biodiesel cars produced the most potent exhaust in terms of oxidative activity. When the DPF was fitted on the Honda Accord diesel vehicle, the mass emission rates and distance-based oxidative potential were both decreased by 98%, compared to the original configuration. Correlation analysis showed that the DTT consumption rate was highly associated with WSOC, WISOC, and OC (R = 0.98, 0.93, and 0.94, respectively), consistent with previous findings.

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Pressure drop modelling is a subject of special Due to the fuel penalty resulting from the increased backpressure of the loaded filter, it is necessary interest for the design and control of diesel particulate for the filter to be regenerated. This regeneration filters. Based on previous experience, an improved pressure involves oxidation of the accumulated particulate, drop model is presented. Special emphasis is given on the which may be periodical or continuous, during soot permeability properties and its dependence on temregular engine operation. The initiation and control perature and pressure. With the assumption of uniform of the regeneration process is the main issue in diesel wall flow distribution throughout the channel length, it filter technology, as regeneration should be as safe is possible to derive an analytic expression for pressure as possible to avoid excessive thermal stresses and drop calculation. The main difference with previously profailure of the filter material. Regeneration systems posed analytic expressions lies in the inclusion of gas are based on the use of catalysts (catalytic coatings density dependence on local pressure, which necessitates or fuel-borne catalysts) to lower the reaction teman iterative calculation procedure. The importance of this perature and/or engine measures (e.g. post-injection) improvement is illustrated parametrically. The new model or electrical heating to increase the exhaust gas is validated against experimental data on an engine bench, temperature. using a double filter configuration to ensure constant filter Understanding the flow phenomena contributing soot loading throughout the test.to the pressure drop in particulate filters is of great importance for the emissions engineer. On the one Key words: diesel engine, after-treatment technology, hand, filter design should target the minimization of exhaust emissions, mathematical modelling, pressure drop pressure drop in real-world conditions by careful selection of filter geometry (volume, cell density, wall thickness, porosity). On the other hand, the

This paper presents a novel partial flow sampling system for the characterization of airborne exhaust particle emissions. The sampled aerosol is first conditioned in a porous diluter and then subsequent ejector dilutors are used to decrease its concentration to the range of the instrumentation used. First we examine the sensitivity of aerosol properties to boundary sampling conditions. This information is then used to select suitable sampling parameters to distinguish both the nucleation and the accumulation mode. Selecting appropriate sampling parameters, it is demonstrated that a distinct nucleation mode can be formed and measured with different instruments. Using these parameters we examine the performance of the system over transient vehicle operation. Additionally, we performed calculations of particle losses in the various components of the system which are then used to correct signals from the instruments. Several quality characteristics are then discussed, such as the repeatability and reproducibility of the measurements and the potential to derive total emission rate with a partial flow sampling system. Comparisons in different laboratories show that repeatability (intra-laboratory variability) is in the order of 10% for accumulation mode particles and 50% for nucleation mode ones. Reproducibility (inter-laboratory variability) values are in the range of ±20-30%. Finally, we compared laboratory size distributions with ambient samples obtained chasing a vehicle. This demonstrated that the sampling system accurately reproduced the accumulation mode particles as well as the potential for nucleation mode formation. This sampling system has