Question
Download Solution PDFThe octane rating is a measure of the ability of the _____ to resist detonation during combustion.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
Octane Rating:
- The S.I. engine fuel has been given an anti-knocking rating which is known as Octane Rating. It basically shows the resistance of the fuel to create knocking by auto-ignition.
- According to standard practice, the antiknock value of an SI engine fuel is determined by comparing its antiknock property with a mixture of two reference fuels, normal heptane (C7H18) and iso-octane (C8H18).
- Iso-octane (C8H18) chemically being a very good antiknock fuel, is arbitrarily assigned a rating of "100 octane number".
- Normal heptane (C7H16) has very poor antiknock qualities and is given a rating of "0 octane number".
- Thus, if the content of Iso-octane is high in the fuel then it will ensure high octane number resulting in better fuel anti-knock quality. Because of the high Octane number, the fuel will not auto-ignite as the possibility of knocking has been diminished by the fuel quality.
- Hence, Iso-octane content in fuel for S.I engine retards auto-ignition.
- The octane rating of petrol is 81.
- The octane rating of LPG is 110.
- The spark-ignition fuels have a high octane rating of 80 to 100 and a low cetane rating of about 20, whereas diesel fuels have a high cetane rating of about 45 to 65 and a low octane rating of about 30.
Last updated on May 28, 2025
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