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It is well known that the optimal management of cold start is crucial to fulfill present and future emission legislation. During past years the catalytic converter has left its original under floor position to get increasingly closer to the engine in order to exploit higher exhaust gas temperature. Simultaneously, the exhaust gas temperature is becoming significantly lower, both in gasoline engines due to the extensive use of turbo charging, and in diesel engines thanks to very high combustion efficiency and in some cases the use of two stage turbo charging. A well established way to reach the catalyst light-off temperature fast enough to fulfill emission limits consists of artificially increasing the exhaust gas temperature. This has the drawback of a higher fuel consumption which conflicts with the tight CO2 targets now required of the OEMs.

The Environmental Protection Agency (EPA) and California Air Resources Board (CARB) requirements for high mileage durability of emission components make it necessary to ensure the mechanical robustness of metallic catalytic converters. In addition, the robustness of design features must be assessed in the early design development phase without resorting to vehicle fleet testing. By following established reliability methods, a new approach for time and cost efficient accelerated durability testing was developed, which can account for the combined effects of critical stressors of a metallic catalytic converter. This paper describes the methodology used to determine the critical stressors and their levels in actual operating conditions which were determined by analyzing a broad range of vehicle test information. This information was used to develop a temperature profile and a high vibration load profile for the new life test method.

Metal based Diesel Particulate Filters (PM-TRAPs) could represent a short time solution to face with particulate (and NOx) emissions with a small influence on CO2 emission. In fact, the operation principle of the PM-TRAP, based on fluid dynamical behavior of exhaust flow in “ad hoc” shaped geometries, allows to separate the particle content of exhaust-gases but needs to be carefully assessed to optimize filter performances. In this paper a mixed numerical and experimental procedure has been developed; it allows to finely tune the design parameters which can be used to achieve pre-defined targets in terms of particulate matter and fuel consumption. By adopting the previously declared procedure, a PM-TRAP “optimal” geometry has been chosen. Its performance has been verified with respect to experimental data. Results are encouraging and suggest further development of the system.

The effects of the internal geometry of catalytic converter channels on flow characteristics; exhaust backpressure and overall conversion efficiency have been investigated by means of both numerical simulations and experimental investigations. The numerical work has been carried out by means of a micro scale numerical tool specifically tailored for flow characteristics within converter channels. The results are discussed with aid of flow distribution patterns within the single cell and backpressure figures along the catalyst channel. The results of the numerical investigation provide information about the most efficient channel shapes. An experimental validation of the simulated results has been carried out with a production 3.6 liter, 6-cylinder engine on a dynamic test bench. Both modal and bag emission data have been measured during the FTP-Cycle.

Particulate Matter (PM) filters are becoming a standard component of Diesel engines exhaust aftertreatment devices to comply with the forthcoming engine emission regulations. However, cost reduction and durability are still critical issues in particular for the integration of the PM-filter with other components of the after-treatment system (e.g. pre-turbo-catalyst, close-coupled-catalyst, PM-filter, SCR). To respect functional (available temperature and gas composition) and space restraints, very complex shapes may result from the design causing tortuous flow patterns and influencing the flow distribution into the PM-filter. Uneven soot distributions in the filter may cause a non-homogeneous development of filter regeneration, leading to failures, for example due to the occurrence of large temperature gradients during the oxidation of soot deposits.