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Diesel particulate traps, when heavily loaded with soot to assure complete incineration, are susceptible to thermal stress failure when regenerated under conditions of high exhaust temperature followed by low exhaust flow. The regeneration characteristics of supplemental electrical igniters, operated by automatic regeneration controls and aided by organometallic fuel additives, have been evaluated on cordierite monoliths and several alternative ceramic trap materials. These regeneration systems were evaluated in an attempt to increase trap durability without the use of invasive engine controls, which can cause performance and fuel economy losses. The regeneration and engine exhaust emission characteristics of cerium and manganese fuel additive mixtures are presented. A discussion of a method of dispensing the additive, and its fuel-stability characteristics, are given, along with a means of predicting trap plugging due to additive ash accumulation on the trap walls.

Concept feasibility of a burner-bypass particulate trap system for a heavy-duty diesel engine has been demonstrated. The success of this demonstration resulted from the development of a new method of controlling the thermal regeneration process which avoids melting, thermal cracking, and thermal fatigue of the cordierite ceramic trap element. Over 300 load and regeneration cycles, simulating more than 100,000 vehicle miles, were accumulated on a single trap element in engine dynamometer tests with no signs of trap deterioration. In vehicle tests with this trap system, vehicle performance was unaffected, exhaust noise was comparable to that of a production muffler, and the fuel economy penalty was less than one percent. Although this system shows promise for providing the durability required for the heavy-duty application, concerns about its cost and complexity remain.

Exhaust aftertreatment will likely be required for the Detroit Diesel Allison 6.2L V-8 diesel engine to meet future light- and heavy-duty particulate and NOx emission standards. As GM's highest-volume diesel automotive engine, the 6.2L power plant is an option for Chevrolet and GMC trucks in both the light- and heavy-duty vehicle emission classes. This paper reviews the application of three different aftertreatment concepts to light-duty trucks: the catalyzed-trap approach, the additive/trap approach, and a newly developed mini-burner/trap system. System design and performance guidelines are presented, along with some construction details for each of the systems. An additive-based vehicle and a burner-based vehicle were tested in a varied but limited range of driving conditions. Both vehicles were equipped with. automated controls to initiate trap regeneration, and both also required additional engine controls to ensure proper emission and regeneration system operation.