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An effective way of meeting future emission legislation with a heavy-duty diesel engine is to equip the engine with an EGR-system combined with a particulate trap. In this study the work was concentrated on the EGR-system. The goal of the investigation was to find an EGR-system that could deliver enough air and exhaust gases to the engine to meet the Euro IV emission levels with minimum penalty on engine performance and fuel consumption, starting from a Euro 0 engine. The tests showed that it was possible to significantly improve emissions with all the tested EGR-systems in combination with a particulate trap, but notable differences with respect to fuel consumption were found. For all EGR systems under study, the main factors influencing engine performance and fuel consumption were found to be. Pumping losses. Residual gases. Temperature of the recirculated exhaust gases. Distribution of the recirculated exhaust gases between the cylinders

Five field-aged catalysts with different mileages were analysed with respect to emission performance and structural changes. The FTP-75 emission results were compared to synthetic exhaust gas tests including: i) light-off, ii) lambda screening at stationary and oscillating stoichiometry, iii) space velocity variation. Several samples from different positions of one catalyst were used to achieve the spatially resolved activity profile for that catalyst. Surface characterisation was used to characterise accumulated catalyst poison. Laboratory space velocity test was concluded to be a sensitive probe for catalyst performance: good correlation to vehicle emission data was found. An analysis of the influence of temperature and λ oscillation on the catalyst conversion performance was made, with particular emphasis on the ageing effects.

Catalysts aged under different on-road conditions were analysed with respect to their conversion of CO and HC at step changes of the synthetic exhaust gas composition. Time resolved diode laser spectroscopy and fast response FID analysis were used to characterise the catalyst response to transient changes of CO and hydrocarbons in the exhaust gas. The oxygen storage capacity was monitored at various conditions; flow rate, catalyst temperature, previous exposure to oxidizing or reducing atmosphere and amplitude of the perturbation. The technique appeared to provide a sensitive probe for analysis of the dynamic oxygen storage capacity of new and aged catalysts at exhaust like conditions. The results correlate well with the transient emission performance during vehicle tests. Further, surface characterization using SEM/EDS and XPS techniques indicated that phosphate formation was the most probable cause of deactivation.

A test method, based on parallel sample testing with exhaust fuel injection and certain test procedures, has been developed for diesel lean-NOx catalyst evaluation purposes. The results of the verification tests show uniform distribution of both the exhaust gas and the injected fuel, and a high degree of fuel evaporation. Test procedures are discussed from several points of view. The test method offers a precise and efficient way of testing lean-NOx catalysts on heavy duty diesel engines.

This paper will review several different emission control systems for heavy duty diesel (HDD) applications aimed at future legislations. The focus will be on the (DOC+CSF+SCR+ASC) configuration. As of today, various SCR technologies are used on commercial vehicles around the globe. Moving beyond EuroVI/US10 emission levels, both fuel consumption savings and higher catalyst system efficiency are required. Therefore, significant system optimization has to be considered. Examples of this include: catalyst development, optimized thermal management, advanced urea dosing calibrations, and optimized SCR inlet NO:NO2 ratios. The aim of this paper is to provide a thorough system screening using a range of advanced SCR technologies, where the pros and cons from a system perspective will be discussed. Further optimization of selected systems will also be reviewed. The results suggest that current legislation requirements can be met for all SCR catalysts under investigation.

The catalytic converter on a European diesel car must operate under extremely variable conditions, ranging from very low temperature during city-driving to high temperature during Autobahn-driving. Therefore, the development of new catalyst technology for European applications requires simultaneous achievement of properties that have long been considered incompatible. In this paper, it is shown how extremely good low temperature activity for CO and hydrocarbons (and VOF), negligible storage of sulfates, and very good thermal durability were obtained simultaneously with an appreciable reduction of NOx. Through the systematic analysis of basic catalytic phenomena, under conditions of relevance to the real-world application, it was possible to control the interaction between support, stabilizers and promoters with the precious metal package in an efficient way. The large-scale manufacturing aspects formed an important part of the development program.

The formation of Nitrous Oxide (N2O) over an aged three way catalyst was analysed in a laboratory reactor for a variety of simulated Otto engine exhaust gas conditions. Nitrous Oxide formation was further analysed during FTP75 dynamometer test with a car. The car was equipped with either an aged catalyst or a fresh one. A fast response diode laser system was modified to enable detection of Nitrous Oxide and Carbon Monoxide simultaneously. From laboratory data the kinetics of Nitrous Oxide formation were evaluated with mathematical simulations and a mechanism was suggested. The results were compared to data from vehicle tests and the results were discussed in the light of the laboratory study. Two general trends were confirmed, i) N2O formation increases at slightly lean conditions: ii) catalysts with a low degree of deterioration gave lower N2O emissions, iii) the extent of N2O formation goes though a maximum with respect to dissociation rate of NO.

This paper describes the development and characterization of a selective catalytic reduction (SCR) catalyst system for a typical EUIV heavy-duty diesel (HDD) engine. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated, before examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. Finally, the durability of the SCR catalyst is described. Taken as a whole, the results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment (EA) solution.

Four samples from each of two field-aged catalysts subjected to different field test conditions were investigated. The light-off and conversion performance of each sample was measured in a synthetic exhaust flow reactor system. Time-resolved laser IR spectroscopy was used to investigate the catalyst behaviour under transient conditions. Significant differences in light-off temperatures and transient conversion performance between the samples was observed. The samples taken from the inlet side of the monolith were more deactivated than the corresponding ones from the outlet. However, samples taken from peripheral positions always showed better performance than samples originating from the centre. In order to explain observed variations in activity, the following surface properties were examined: oxygen uptake, specific metal area (CO chemisorption), total surface area (BET) and chemical composition (XPS analysis).

A standard commercial three-way catalyst was aged at 950°C for 24 hours in dry N2 with 2% O2. The performance of the aged and a fresh samples were characterized using a synthetic exhaust flow system. The light-off temperature for all three pollutants on the aged sample was more than 70°C higher than for the fresh one. The effect of aging on steady-state performance at higher temperatures (>400°C) was more moderate. In order to explain the decrease in activity the samples were analysed for their bulk and surface composition using electron microscopy (TEM/STEM/EDS), photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In addition the precious metal dispersion were determined by CO chemisorption and the total area by standard BET measurement. TEM micrographs showed that the metal particles containing platinum had an average diameter between 3-4 nm in the fresh sample but grow considerably in size upon aging.

This paper describes the development and characterization of a Selective Catalytic Reduction (SCR) catalyst system for EUIV (HDD) engines. The performance of the SCR catalyst and the impact of catalyst volume are described. The effect of using an ammonia slip catalyst behind the SCR catalyst is investigated. The durability of the SCR catalyst is described. Finally, examples of the use of computer modelling to refine the optimum volume and urea injection strategy are given. The results demonstrate how a combination of practical experiments and computer modelling can be used to refine the system and provide a cost-effective exhaust aftertreatment solution.