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A Novel Accelerated Aging System to Study Lubricant Additive Effects on Diesel Aftertreatment System Degradation
Abstract:
The challenge posed by the long run times necessary to accurately quantify ash effects on diesel aftertreatment systems has led to numerous efforts to artificially accelerate ash loading, with varying degrees of success. In this study, a heavy-duty diesel engine was outfitted with a specially designed rapid lubricant degradation and aftertreatment ash loading system. Unlike previous attempts, the proposed methodology utilizes a series of thermal reactors and combustors to simulate all three major oil consumption mechanisms, namely combustion in the power cylinder, evaporative and volatile losses, and liquid losses through the valve and turbocharger seals. In order to simulate these processes, each thermal reactor allows for the precise control of the level of lubricant additive degradation, as well as the form and quantity of degradation products introduced into the exhaust upstream of the aftertreatment system.
To demonstrate the utility of this system, individual exhaust ash and particulate samples, generated from the stock engine as well as with the accelerated ash loading system, were collected and analyzed using a number of techniques including TGA, TEM, and SEM-EDX. This analysis follows a systematic approach to understanding the similarities and differences between the ash compounds present in conventional diesel exhaust and the ash species generated using the accelerated loading system. More importantly, the results of this study provide insight into the manner in which specific accelerated oil consumption mechanisms influence particle and ash characteristics. This work presents a unique approach to the development of a realistic accelerated lubricant degradation system, in order to carefully control and condition the nature of the exhaust. Lastly, the application of this methodology to accelerate the ash loading and aging of PM and NOx aftertreatment systems is discussed.