- Calculated Carbon Aromaticity Index
The calculated carbon aromaticity index (CCAI) is an index of the ignition quality of residual fuel oil.
The running of all
internal combustion engines is dependent on the ignition quality of the fuel. Forspark-ignition engines the fuel has anoctane rating . Fordiesel engine s it depends on the type of fuel, for distillate fuels thecetane number s are used. Cetane numbers are tested using a special test engine and the existing engine was not made for residual fuels. For residual fuel oil two other empirical indexes are used: CCAI andCalculated Ignition Index (CII). Both CCAI and CII are calculated from thedensity and kinematic viscosity of the fuel.Definition
Formula for CCAI:
CCAI=D-140.7 log (log (V+0.85))-80.6-210 ln left (frac{t+273}{323} ight )
which is equivalent to:
CCAI=D-140.7 log (log (V+0.85))-80.6-483.5 log left (frac{t+273}{323} ight )
Where:
D= density at 15°C (kg/m3)
V= viscosity (cST)
t = viscosity temperature (°C)
word upUse
This will normally give a value somewhere between 800 and 880. The lower the value is the better the ignition quality. Fuels with a CCAI higher than 880 are often problematic or even unusable in a diesel engine. CCAI are often calculated under testing of marine fuel.
Wikimedia Foundation. 2010.