Heavy Duty Diesel After-Treatment System Analysis Based Design: Fluid, Thermal and Structural Considerations

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. The design details such as strategies for changing the flow characteristics in front of DOC such that the flow uniformity/characteristics in front of the catalyst brick are improved with minimal impact on the back pressure. The conjugate heat transfer analysis is also carried out to calculate the temperature distribution in the entire system considering the forced fluid flow, conductivity in the solid medium, convection and radiation. Few case studies of the predicated temperature distribution in the system with the experiments are also given.

The second part of this study involves performing analytical durability tests, to ensure the proper durability behavior of thermal and mechanical performance. The temperatures inside the entire system consisting of DOC (Diesel Oxidation Catalyst), SCR (Selective Catalytic Reduction) and DPF (Diesel Particulate Filter) are also discussed; these are extremely high under the harsh conditions. Different detailed designs of the system are investigated with respect to structural behavior under both thermal and road load conditions in order to find a durable and cost-effective solution for series production. The experimental validations of the designs developed are also discussed.