> Among all the chat about politics ,SUV's and such a question about biodiesel. > Is there such a thing as an 0ctane rating similar to gas. > How does one know if the brew is OK. > Jim........
Thanks again Steve! Did the google search and that report "Cetane Number Testing of Biodiesel" by Jon Van Gerpen* http://www.biodiesel.org/resources/reportsdatabase/reports/gen/gen-187.pdf looks interesting. Here's a report that helps explain Cetane/Octane -- "Alternatives to Traditional Transportation Fuels: An Overview" June 1994 149 page, 1239K PDF > http://tonto.eia.doe.gov/FTPROOT/alternativefuels/0585o.pdf Cetane The combustion and ignition characteristics of diesel engine fuels are expressed in the cetane number. Fuels with high cetane numbers have low autoignition temperatures and short ignition delay times. Since a high octane number means a low cetane number (see Chapter 7), Cetane Number The most important engine performance property of diesel is the cetane number, which is a measure of the ease with which fuel will self-ignite under compression. The delay between the time the fuel hits the hot compressed air and when it ignites depends to a large extent on hydrocarbon composition. The higher the cetane number, the shorter the ignition delay and the better the engine performance. Cetane number is highest for linear paraffins, and lowest for aromatics as shown below: Fuel Component Contribution to Cetane Number Aro- Naph- Branched Linear Branched Linear matics thenes Olefins Olefins Paraffins Paraffins -----------------Increasing Cetane Number----------------> <-----------------Increasing Octane Number---------------- A high octane number, desirable for gasoline, means high aromatics and low linear paraffins, whereas the opposite is true for cetane numbers. Higher aromatic content means a lower cetane number and poorer diesel engine performance, as well as increased particulate formation. In spark-ignition engines, aromatics are good for engine performance but bad for emissions. In compression-ignition engines, aromatics are bad for both performance and emissions. Thus, in the case of diesel, there is no tradeoff between performance and emissions regarding aromatics. Low cetane number and associated long ignition delay cause rough engine operation, misfiring, and incomplete combustion in a cold engine at low temperatures, resulting in power loss and exhaust smoke. _______________________________ Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
