Cetane Index
Cetane index, abbreviated as CCI, is a measure used to estimate the ignition quality of diesel fuel. It correlates with the cetane number, which is the primary indicator of diesel fuel’s combustibility, but the cetane index is calculated rather than directly measured. The cetane index is widely used to gauge fuel quality, often in cases where additives are not present, as they can affect combustion properties but may not influence the cetane index directly.
Key Points about Cetane Index
Purpose - The cetane index gives an approximation of how easily diesel fuel will ignite and how smoothly it will burn in engines. Higher cetane values indicate fuel that ignites more easily, leading to better performance, especially in cold weather and under load.
Calculation - It’s calculated based on the density and distillation properties of the fuel, without requiring engine tests. The exact formula varies but generally uses factors like the fuel’s density and boiling points.
Range - Cetane indices are generally in the range of 30 to 60. Diesel engines typically perform well with a cetane number around 40–55, although some high-performance or heavy-duty engines may require higher values.
Difference from Cetane Number - Unlike the cetane number, which is determined through specific testing methods, the cetane index is a calculated estimate. It may be less accurate than actual testing, but it provides a useful approximation, especially in cases where actual cetane number measurements are impractical.
Cetane Index formula |
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| \( CCI \;=\; ( 454.54 - 1640.6 \; SG ) + ( 774.74 \; A ) - 0.554 \) | ||
| Symbol | English | Metric |
| \( CCI \) = Cetane Index | \(dimensionless\) | - |
| \( SG \) = Specific Gravity at 60 °F | \(dimensionless\) | - |
| \(A\) = Aniline Point at °F | \(F\) | - |
Tags: Refinery