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This paper gives an overview of the development work for a diesel after-treatment system, used in heavy duty trucks to fulfill the new US emissions limits. The paper starts with the description of design evaluation and optimization studies on heavy duty diesel exhaust after-treatment system using numerical simulation. The studies involve initial conceptual design evaluation of the entire after-treatment system for fluid flow, temperature distribution, and subsequent structural loads. Computer modeling, as complementary approach to prototyping and experimental investigations, helps to make basic design decisions and therefore to shorten the overall development process. The numerical simulation involves computational fluid dynamics (CFD) analysis for fluid flow and temperature distribution and finite element analysis (FEA) for subsequent structural analysis. The first part of the paper involves computational fluid dynamic optimization study related to diesel exhaust system.

In order to meet the mandated EPA2010 emissions for heavy duty commercial vehicle regulations, most applications require very large, complex, yet compact exhaust after-treatment systems. These systems not only contain the necessary substrates and filters to perform the proper emissions conversion, they also typically will consist of mixing pipes and internal reversing chambers all within very tight space proximity. Some of these systems are able to accomplish the complete emissions reduction and conversion within a single, large packaging unit. While there are advantages in fuel efficiency and perhaps overall packaging with these “single box” units, the disadvantage of these types of designs is that it prohibits many internal components from cooling down by the outside environment, which can pose thermal mechanical durability challenges.