Difference between Octane and Cetane number | Octane and Cetane Number

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By chempeers.com

Difference between Octane and Cetane number

Octane Number:

  • Mixture of n-heptane containing %age of Iso-octane in which knocking is same as sample of petrol.
  • Consumption of fuel is measured in it.
  • It tells us about knocking of engine.
  • For gasoline, octane number is used.
  • Octane number of iso-octane as 100 tells octane rating.
  • Fuel having low cetane number has high octane number
  • Octane number is 85 for motorcycle and car and 100 for aero plane and helicopter of good petrol.
  • Addition of toluene or benzene increases the octane number of  petrol.
  • Fuel of high octane number do not allow pre-ignition under high pressure and temperature.
  • Spark ignition engine uses petrol of high octane number which is also known as internal combustion engine or petrol engine. In this engine, pre-ignition will be less due to chemical delay.

Cetane Number:

  • Mixture of n-hexadecane and 2-methyl naphthalene containing %age of n-hexadecane having similar ignition properties like sample of diesel.
  • Delay of fuel ignition is measured in it.
  • It predicts the ignition of engine.
  • For diesel, cetane number is used.
  • Ignition of n-hexadecane as 100 tells cetane rating.
  • Fuel having low octane number has high cetane number.
  • cetane number is 25 for medium-speed engine and 45 for high-speed engine of good diesel..
  • Addition of ethyl nitrate and acetone per oxide increases the cetane number of diesel.
  • There is a low resistance to pre-ignition of fuel having high-octane number. More power from fuel is  obtained from fuel having high octane and cetane number.
  • Compression engine use fuel of high cetane number which is also known as diesel engine. Combustion reaches to maximum value when chemical and physical  delay is present in the engine and a sudden blast may occur.

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