Cetane number is one of the main parameters of diesel fuel, which indicates its combustibility. In the physical system, this number indicates the time it takes from the moment of injection into a cylinder to the beginning of fuel ignition. The higher the cetane number, the less the delay of mixture ignition. The scale of this parameter is 0 to 100. According to European standards, 51 is the minimum for diesel fuel.
If the cetane number is less than 40, such fuel is ruinous to the engine. Ignition delay increases sharply, pressure in the combustion chamber rises, piston assembly wear accelerates. At the same time, if the cetane number is too high, problems also arise, such as incomplete combustion, formation of soot, increased fuel consumption and smoke in the exhaust.
Determining diesel fuel cetane number
The most reliable method of cetane number measurement is by using a special calibrate engine. The results are used to calibrate other cetane number measurement devices, such as infrared spectrometers.
Since 2009 the engine method has been modified, based on ignition delay. The new process shows good convergence, repeatability and takes less time (measurement time reduced by 20 minutes).
Cetane number can also be measure by non-engine related methods. However, in this case the result is heavily influenced by the composition of the diesel fuel. In this respect the engine method is better: it allows to correctly measure the cetane number of any fuel.