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The introduction of stringent EPA 2015 regulations for locomotive / marine engines and IMO 2016 Tier III marine engines initiates the need to develop large diesel engine aftertreatment systems to drastically reduce emissions such as SOx, PM, NOx, unburned HC and CO. In essence, the aftertreatment systems must satisfy a comprehensive set of performance criteria with respect to back pressure, emission reduction efficiency, mixing, urea deposits, packaging, durability, cost and others. Given multiple development objectives, a systematic approach must be adopted with top-down structure that addresses top-level technical directions, mid-level subsystem layouts, and bottom-level component designs and implementations. This paper sets the objective to provide an overview of system development philosophy, and at the same time touch specific development scenarios as illustrations.

In order to scientifically approach the design of mounting systems for substrates in emissions control systems, it is essential to characterize the behavior of the involved materials, particularly the support mat. Manufacturing processes and various in-field conditions impact the long term performance of the support mat, and life-long emissions performance is critically dependent on its ability to retain the substrate throughout the intended life. Therefore, to ensure product robustness, the behavior during operation of all available support mats must be appropriately characterized to determine the technical layout in specific applications. This paper addresses three common characterization tests, developed internally and externally. Additionally, equipment improvements to minimize artifacts in test results as well as the development of a new mat test for manufacturing methods are addressed.

EPA 2015 Tier IV emission requirements pose significant challenges to large diesel engine after treatment system development with respect to reducing exhaust emissions including HC, CO, NOx and Particulate Matter (PM). For a typical locomotive, marine or stationary generator engine with 8 to 20 cylinders and 2500 to 4500 BHP, the PM reduction target could be over 90% and NOx reduction target over 75% for a wide range of running conditions. Generally, HC, CO and PM reductions can be achieved by combining DOC, cDPF and active regeneration systems. NOx reduction can be achieved by injecting urea as an active reagent into the exhaust stream to allow NOx to react with ammonia per SCR catalysts, as the mainstream approach for on-highway truck applications.