In the maritime and shipping industries, fuel quality is crucial for efficient engine performance and safety. The Calculated Carbon Aromaticity Index (CCAI) serves as a key indicator of the combustion quality of marine and residual fuels, akin to how the Cetane number is used for diesel fuels. The CCAI helps predict the ignition quality of fuel oil, providing essential data to engineers and ship operators for optimizing fuel consumption and minimizing engine wear.
What is CCAI and Why is it Important?
The CCAI is a numerical index calculated from the fuel’s density, kinematic viscosity, and temperature. These parameters together give insights into how well the fuel will perform in marine engines. A lower CCAI indicates better ignition characteristics, similar to a higher Cetane number in diesel, which means the fuel is more likely to ignite and burn efficiently under engine conditions.
The Formula and Calculation Process
To understand and calculate the CCAI, the following inputs are needed:
- Density ((\rho)): Measured in kilograms per cubic meter (kg/m³), it indicates how compact the fuel is.
- Kinematic Viscosity ((\nu)): Measured in centistokes (cSt), it shows how thick the fuel is.
- Temperature ((t)): The measurement condition for the viscosity, usually at 50°C.
The formula used for calculating CCAI is:
[ CCAI = d – (3 \times v \times \log_{10}(v) \times (t + 273)) ]
Where:
- (d) is derived from the density and calculated as (d = 4870 \times \left(\frac{\log_{10}(\rho)}{\log_{10}(891)}\right)).
- (v) is the kinematic viscosity.
- (t) is the temperature in Celsius added to 273 to convert it to Kelvin.
Step-by-Step Example
Let’s calculate the CCAI for a hypothetical fuel sample with the following properties:
- Density: 990 kg/m³
- Kinematic Viscosity: 180 cSt
- Temperature: 50 °C
Steps:
- Calculate the logarithm (base 10) of the density: ( \log_{10}(990) ).
- Find (d) using the density formula: ( d = 4870 \times \left(\frac{\log_{10}(990)}{\log_{10}(891)}\right) ).
- Calculate the logarithm (base 10) of the viscosity: ( \log_{10}(180) ).
- Compute the CCAI: ( CCAI = d – (3 \times 180 \times \log_{10}(180) \times (323)) ).
This process will yield a CCAI value, indicating the fuel’s ignition quality.
Relevant Information Table
| Property | Symbol | Unit | Typical Value |
|---|---|---|---|
| Density | ( \rho ) | kg/m³ | 890 to 1010 |
| Kinematic Viscosity | ( \nu ) | cSt | 120 to 380 |
| Temperature | ( t ) | °C | 50 |
Conclusion
The CCAI calculator is a crucial tool in the maritime industry, helping to ensure that the fuels used are of a quality that promotes efficient engine operation and safety. By understanding and using the CCAI, marine engineers can better manage fuel handling and optimize combustion processes, leading to reduced operational costs and lower environmental impact. The straightforward calculation and ability to predict fuel performance make the CCAI an invaluable resource in fuel quality assessment.