As agencies and governing bodies evaluate the feasibility of reduced emission standards, additional focus has been placed on technology durability. This is seen in proposed updates, which would require Original Equipment Manufacturers (OEMs) to certify engine families utilizing a full useful life (FUL) aftertreatment system. These kinds of proposed rulings would place a heavy burden on the manufacturer to generate FUL components utilizing traditional engine aging methods. Complications in this process will also increase the product development effort and will likely limit the amount of aftertreatment durability testing. There is also uncertainty regarding the aging approach and the representative impact compared to field aged units. Existing methodologies have evolved to account for several deterioration mechanisms that, when controlled, can be utilized to create a flexible aging protocol. As a result, these methodologies provide the necessary foundation for continued development.
The Diesel Aftertreatment Accelerated Aging Cycle (DAAAC) protocol considers thermal loading, lubricant derived poisoning, and sulfur exposure as integral elements for aftertreatment aging. Combining these elements simulates deterioration mechanisms observed during normal vehicle operation. In doing so, these elements are introduced at an accelerated rate to reduce aging duration by a factor of ten. The following case study will consider a special application of the DAAAC protocol for an advanced aftertreatment technology demonstration. Since these technologies normally have limited field data to guide the aging cycle development process, they bring about several challenges. This includes understanding the implication of the technology on the overall system, as well as, limitations from unknown service practices. To discuss this topic in detail, an example from the CARB low NOX stage 1 demonstration program will be referenced as part of this this work. It will show that ensuring proper deterioration mechanism exposure is important to assess the overall system performance.