Diesel Particulate Filter System - Effect of Critical Variables on the Regeneration Strategy Development and Optimization

Regeneration of diesel particulate filters poses major challenges in developing the particulate matter emission control technology to meet EPA 2007/2010 emissions regulations. The problem areas are multifold due to the complexity involved in designing the filter system, developing regeneration strategies and controlling the regeneration process. This paper discusses the need for active regeneration systems. It also addresses several key limitations and trade-offs between the regeneration strategy, chemical kinetics, exhaust gas temperature and the regeneration efficiency.

Passive regeneration of diesel particulate filter systems is known to be highly dependent on the engine-out [NOx/PM] ratio as well as exhaust temperature over the duty cycle. Using catalytic oxidation of auxiliary fuel injected into the system, the exhaust gas temperature can be successfully enhanced for filter regeneration. However, as demonstrated in this work, such active temperature increase may be either beneficial or detrimental to the efficiency of regeneration, depending on the mechanism of particulate matter oxidation. Engine tests and bench reactor results were used to understand this effect. This information should help provide tools for developing optimum regeneration strategies for different applications based on the engine emission characteristics, duty cycle and type of the filter system.