Search Results

The Urea Selective Catalytic Reduction (SCR) technology is one of the major mature exhaust aftertreatment technologies which are demonstrated to be able to lower tail pipe NOx emission by 90%. The system consists of a urea injection at upstream pipe and a downstream SCR converter. A well mixed flow (exhaust gas and NH3) in front of SCR substrate, which is usually constrained by tight design packaging, is very critical to ensure the desired performance. Current paper addresses the geometrical effects on flow mixing by using three dimensional Computational Fluid Dynamics (CFD) tool. The mixing enhancement is achieved by adding flow mixer. The shapes and locations of flow mixers, as well as the number of blades inside mixer are investigated to show the effect on fluid mixing in downstream along the flow direction. Results show great improvement of flow mixing by adding a delta wing mixer.

Computational Fluid Dynamics (CFD) is becoming a very popular tool for numerical predictions of flow distribution, pressure loss, heat transfer, internal and external combustion and has been widely used in automotive, aerospace, marine and even medical industries. In automotive industry, CFD tool is used and customized in five major areas: vehicle aerodynamic effect; thermal management (cooling and climate control); cylinder combustion; engine lubrication and exhaust system performance. Current paper will focus on CFD applications in one of vehicle subsystems - exhaust system. Increasingly stringent emission requirements are enforced by Environment Protect Agency (EPA) to reduce harmful chemical components such as CO, NO, NO2. Exhaust systems are becoming more complicated and usually consist of one or multiple catalytic converters with one or multiple substrates inside.

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 this paper, a combined analytical CAE procedure and durability experiments are used to calculate the durability of complete exhaust system. Detailed analytical calculations are carried out and the results are explained for the typical exhaust system components considering the durability loads such as engine vibration loading, proving ground road loads, thermal loads, loads created due to geometric dimensioning and tolerances (GD & T), and bolt loads. The durability issues associated with the exhaust system components such as hot-end brackets, converter cone-pipe region, exhaust pipe system, muffler-pipe system, muffler hanger designs, and residual stresses in an exhaust system assembly such as ball joint flange-flange interface, and hot-end converters are explained in detail. Both experimental results and analytical calculations are carried out.