A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

OCTANE NUMBER

DOI: 10.1615/AtoZ.o.octane_number

In a petrol engine, under certain operating and ambient conditions,knock may occur which can cause damage to the engine. Its occurrence depends as well on engine and fuel properties. A measure of the anti-knock performance of a fuel in a given engine is given by its octane number: the higher the octane number, the higher the resistance to knock. A scale has been devised in which automotive fuels are assigned an octane number, which is based on two hydrocarbons defining the ends of the scale: normal heptane (n-C7H16) which has a value of zero and iso-octane (C8H18 2, 2, 4-trimethylpentane) with an octane number of 100. Blends of these two hydrocarbons define the knock resistance, e.g., a blend of 10% n-heptane and 90% iso-octane by volume has an octane number of 90.

The octane number of a fuel is determined in a standard test engine (single-cylinder, variable compression ratio CFR engine developed under the auspices of the Cooperative Fuel Research Committee in 1931) by means of either the research method (ASTM D-2699; BS 2637) or the motor method (ASTM D-2700; BS 2638). The corresponding research octane number (RON) and motor octane number (MON) are obtained under different test conditions which are summarized in Table 1. [Heywood (1988) and Owen and Coley (1990)]. Typical octane numbers for automotive fuels are given in Table 2. A worldwide summary of octane ratings is published regularly by the Associated Octel Co. Ltd, London.

Table 1. Operating conditions for research and motor methods

Table 2. Typical octane numbers*

*Typical octane numbers

REFERENCES

Heywood, J. B. (1988) Internal Combustion Engine Fundamentals, McGraw Hill.

Owen, K. and Coley, T. (1990) Automotive Fuels Handbook, Society of Automotive Engineers

References

  1. Heywood, J. B. (1988) Internal Combustion Engine Fundamentals, McGraw Hill.
  2. Owen, K. and Coley, T. (1990) Automotive Fuels Handbook, Society of Automotive Engineers
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