Development of an Actively Regenerating DPF System for Retrofit Applications 2006-01-3553

Diesel Particulate Filters (DPFs) such as the Continuously Regenerating Technology (CRT^®) particulate filters are known to be highly effective in reducing PM emissions from diesel engines. Passive DPFs such as the CRT filter operate by collecting soot in the filter and subsequently oxidizing this soot in the presence of NO₂ generated by an upstream Diesel Oxidation Catalyst (DOC). Both the NO₂ generation and subsequent soot oxidation reactions require a certain minimum exhaust temperature. In addition, the engine out NO_x to PM ratio is also critical for continuous and successful regeneration of the filter. However, these criteria may not always be met, particularly on low temperature applications such as refuse vehicles and newer low NO_x (2.5 g/bhp-hr NO_x) engines.

This paper discusses the development of an actively regenerating diesel particulate filter (ACR-DPF) system for retrofit applications on heavy duty diesel vehicles. The system is designed using a basic CRT filter system with an integrated fuel injection based active regeneration system. The active regeneration system utilizes atomized diesel fuel that is injected upstream of the CRT to produce an exothermic reaction across the DOC. This increases the exhaust temperature, which allows for periodic O₂-based soot oxidation in the filter, in addition to normal NO₂-based regeneration.

ACR-DPF development included the evaluation of various trigger strategies for regeneration, the development of fuel injection maps, and optimization of the regeneration strategy for minimum HC slip. The performance was evaluated both in engine dynamometer tests and on-road field trials. Transient test cell data, along with data from an on-road demonstration on refuse vehicles at Department of Sanitation in New York and transit buses in Sweden is presented.