Course: BFM 202 Biodiesel Production

Lecture

Cetane Number
Credits
BFM 202 Biodiesel Production Unit 1 Reading has been adapted from "ENGY 131 Unit 1 Commentary: What is biodiesel?" by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Cetane Number

Fuels are differentiated by their heat of combustion and cetane number. The cetane number refers to the
ignition quality of petrodiesel. The diesel engine relies upon complete combustion of a high quality fuel for normal operation. The cetane number measures a fuel's ignition delay when ingected into the cmbustion chamber. The higher the CN, the easier the fuel ignites.

The cetane scale is a dimensionless number that describes the number of fatty acid methyl esters (FAME) in biodiesel and is determined by using a test method called gas chromatography. The CN should normally be in the range of 15 and 100 with U.S. diesel engine manufactures specifying a CN of 45 - 55 although some references indicate 40 - 50.

Cetane reference numbers are:

- Regular diesel = 48
- Premium diesel = 55
- Synthetic diesel = 55
- B100 = 55
- B20 = 50

If the CN is too high, incomplete combustion and smoke occur which indicates that the fuel and air are not mixed properly. If the CN is too low, the engine warms up slowly, operates roughly, misfires, has higher air temperatures, and incomplete combustion occurs.