Detonation means the sudden and violent knock experienced in a Petrol Engine, due to the Anti-Ignition of a portion of the Fuel.
In automobile engineering, octane value plays a very important role. This is mainly important in Spark Ignition Engines.
To find it out, two Fuels, the iso-octane, and the normal Lepton are selected for this purpose under modern practice.
So, The Importance of Octane Value in I.C.Engine is
The iso-octane has a little tendency towards detonation while Lepton readily detonates.
The actual fuel whose O. V is to be determined is first used to run the standard engine and the conditions under which detonation occurs are noted.
The Detonation intensity is measured by the “Knock Meter”.
Then several mixtures of iso-octane and normal Heptanes mixed up in different proportions are used in the same engine, under the same conditions, as before.
So, by making several trials, the mixture which gives the same intensity of Detonation is found.
The percentage of iso-octane in this mixture gives the octane value of the fuel.
For example, with the mixture containing 75% of Iso-Octane and 25% of normal Heptanes, the O. V. of the Fuel will be 75.
Higher the Octane Value, so, the higher the Anti-knocking property of the Fuel.
The Octane values of the pure iso-octane and normal Heptanes are 100 and 0 respectively.
The Octane rating indicates the quality of the petrol to resist detonation.
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