Interesting Behavior of Biodiesel Ignition Delay and Combustion Duration
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This article describes the study of combustion behavior in a production diesel engine using either 100% biodiesel or 100% petroleum diesel. Biodiesel remains a topic of interest, with specific emphasis placed on its conventionally observed higher nitrogen oxides (NOx) emissions. This study's objective is to contrast biodiesel's ignition delay and combustion duration behavior to that of petroleum diesel's by investigating the rate of heat release information from various engine load and speed conditions of a medium-duty diesel engine. Further, the study attempts to support a potential link between biodiesel's burn rate and the observed increase in its exhaust nitric oxide (NO) concentrations. The study observes biodiesel's ignition delay, in accordance with literature, is consistently shorter than petroleum diesel's ignition delay. Further, biodiesel's mid to high load operating conditions have consistently shorter combustion durations. The shorter combustion durations result from the observed faster diffusion burn rate of biodiesel. Biodiesel's low load conditions appear to have nearly the same or longer combustion durations. It is postulated that this occurs from biodiesel's shorter ignition delay, which creates a relatively lower premixed burn fraction; because the low load condition is predominantly premixed, the small increase in diffusive burning is not substantial enough to accelerate biodiesel's overall burn duration. It is speculated that biodiesel's faster diffusion burn rate is a contributor to the observed increases in its exhaust NO concentrations; simple analysis of phenomenological evidence typically supports this potential effect. © 2010 American Chemical Society.
author list (cited authors)
Bittle, J. A., Knight, B. M., & Jacobs, T. J.