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	Statistical field data analysis
	Graph displaying failed active regenerations
	Accelerated test cycle data

Because a coked exhaust injector may result in failed active filter regenerations, engineers at Southwest Research Institute (SwRI) took on a project to develop accelerated test cycles that would replicate exhaust injector coking failure and provide solutions to the problem.

To achieve reliable and robust diesel particulate filter (DPF) regeneration, the aftertreatment system must have active regeneration capability. During the active regeneration, soot is oxidized by oxygen. The reaction can occur only when the exhaust gas temperature is high enough. For a catalyzed filter, the temperature can be about 500–550°C. For non-catalyzed filter, the temperature can reach 600–650°C. The increased exhaust gas temperature needed for active regeneration can be achieved by combusting an additional quantity of diesel fuel.

There are a couple of ways to provide the additional quantity of fuel to increase exhaust temperature. Post-injection (in-cylinder injection) is typically used by passenger cars. In medium-duty and especially in light-duty applications, low system cost is more important and there is less concern about the impact of oil dilution on engine durability. For heavy-duty applications, injecting fuel into the exhaust system (in-exhaust injection) is preferred because of the lack of oil dilution.

For heavy-duty diesel (HDD) applications, an active regeneration control system usually consists of:

• Diesel oxidation catalyst (DOC)

• DPF

• In-exhaust injector, also referred to as:

  • External fuel doser

  • #7 injector

  • Aftertreatment/auxiliary hydrocarbon injector

• Temperature sensors

• Differential pressure sensor across DPF

• Control module

The in-exhaust injector is the control system actuator. Changes in its physical characteristics will have adverse effects on the control system performance. Solutions to mitigate/eliminate the injector coking issue are badly needed. To meet those needs, SwRI built accelerated engine test cycles that replicate exhaust injector coking failure so possible solutions could be evaluated.

For more information about our powertrain control capabilities, or how you can contract with SwRI, please contact Jayant Sarlashkar at jsarlashkar@swri.org or (210) 522-5506.

powertraincontroltech.swri.org

| Engine and Vehicle R&D Department | Engine, Emissions & Vehicle Research Division | SwRI Home |

Southwest Research Institute^® (SwRI^®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

December 28, 2012