Cetane number
The cetane number is determined by the flammability of the fuel. This is a purely proportional number; it is set as follows.
The flammable fuel cetane is assigned the number 100. and the extremely flammable fuel methylnaphthalene is assigned the number 0.
The cetane number indicates how many volume percent of cetane should be mixed with a reference fuel that has the same flammability. like the tested fuel (in our case, diesel).
Little difference
The question is often raised: why can't pure gasoline be used in a diesel engine? You can answer simply.
The flammability of the fuel should be low in a carburetor engine, and on the contrary, high in a diesel engine.
Fuel with high flammability would give in a carburetor engine, as a result, knocking and detonation, which damages the engine, the fuel would ignite itself already during the upward movement of the piston and "didn't wait" sparks from a spark plug. After all, an igniting spark slips only when the piston is in the upper position in the cylinder.
As already mentioned, a diesel engine compresses only clean air. When the piston is at the top and the air is most compressed and therefore very hot, fuel is injected. Auto-ignition should now occur quickly. Thus, the fuel should have good auto-ignition.
Instruction. You may have already noticed with annoyance that when filling the tank of a car, diesel fuel is prone to foaming. Often the tank even overflows. This is due to the higher density of the fuel. Diesel fuel has a higher surface tension than gasoline. When poured into the tank, all types of fuel entrain air to the same extent, but diesel, due to its high density, can only release air relatively slowly. Because of this, unwanted bubbles appear. Therefore, such advice: slowly pour fuel into the tank.
Diesel fuel and temperature
Each fuel is made up of many different hydrocarbon compounds. Diesel fuel contains paraffins.
A negative property of paraffins is their tendency to crystallize more and more at low temperatures. Crystals grow and, starting from a certain temperature, solidify like jelly. The fuel thickens and does not pass through the filter and pipelines. The diesel engine stops.
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