Critical Performance and Durability Parameters of an Integrated After treatment System used to Meet 2007 Tier II Emission Standards

Over the last decade, diesel engine emissions have been reduced significantly. The Tier II emissions requirements drive very low levels of NOx, PM, and NMHC. Meeting these standards with changes in engine operation and architecture is not feasible, thus exhaust after treatment systems are required. Key to successful application of after treatment systems is the thorough integration of the engine and after treatment system operation, and a detailed understanding of the critical parameters controlling emissions reduction. The objective of this paper is to present the results of an integrated after treatment system used to meet 2007 EPA emissions standards for a diesel engine. In this paper, the functional aspect of each after treatment system component will be described followed by a description of the total system function in order to lay the foundation for understanding the integration of the after treatment system with the engine. Discussed will be key after treatment performance and durability aspects and several durability test protocols developed to gain key insight into after treatment system durability. Results from the durability testing indicate that accurate and precise control of several critical parameters of the after treatment system, particularly during active regeneration, is necessary to maintain effective control of tailpipe emissions, and to maintain 2007 emission levels to the useful life of the product.