Development of an EGR and Post-Injection Control System for Accelerated Diesel Particulate Filter Loading and Regeneration on Heavy-Duty and Light-Duty Diesel Engines, 03-9508

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Principal Investigators
Reggie Zhan
Yiqun Huang

Inclusive Dates:  10/01/04 – 09/30/05

Background - The diesel particulate filter (DPF) has emerged as a critical aftertreatment system allowing engines to meet the 2007 diesel vehicle emissions standards in the United States. DPFs filter diesel particulate matter (PM) from diesel exhaust gas. When the accumulated PM reaches a certain level, it must be regenerated for the engine to maintain efficient operation. DPF regeneration is a risky operation, and the DPF can easily be damaged if the regeneration is not controlled properly.

Approach - The objective of this project was to develop a comprehensive strategy to regenerate the DFP completely and safely under any given engine operating conditions. To achieve this goal, the SwRI Rapid Prototyping Electronic Control System® (RPECS)-based engine control system was established on a MY2004 Renault 2.0L common-rail diesel engine to perform in-cylinder post-injection (PI), which is a necessary tool for DPF on-board regeneration. 

To resolve PI associated lubricant dilution problems, an alternative solution, in-exhaust supplementary fuel injection (SFI) was developed on a MY2000 PSA common-rail diesel engine, and it was successfully used to perform DPF regenerations. The SFI system developed through this project was proven to be applicable to DPF regeneration testing and applications in a wide range of light-duty and heavy-duty diesel engine systems.

Extensive chemical reaction and fluid dynamics analysis were used to investigate DPF behavior in PM loading and regeneration stages. The Renault and PSA engines were used to create the real-world worst-case conditions for DPF regeneration and to validate the technical solutions developed.

Accomplishments - Three DPF regeneration failure modes, or uncontrolled regeneration modes, were defined and the root causes of such failures were identified through chemical reaction engineering and fluid dynamics analysis. The three uncontrolled DPF regenerations are:

Type A: Exotherm at the start of regeneration, caused by high SOF content in particulate and high temperature ramp-up rate at the start of regeneration

Type B: Conventional runaway regeneration, caused by the combination of high PM loading level, high O2 concentration, and low exhaust flow rate at idle conditions

Type C: "hot spot" related DPF failure, caused by uneven exhaust flow velocity and temperature distributions during both loading and regeneration processes

Technical solutions to control DPF regeneration under any engine operating condition were developed and validated, such that each of the defined DPF failures were able to be avoided. During this project, a comprehensive approach for DPF safe and complete regeneration was developed.

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