By Engr Matahula, Smart Pwashemeno on Specific fuel Consumption On Merchant Ships
To calculate specific fuel consumption (SFC) on merchant ships, you need to follow these steps:
- Determine the total fuel consumption: Measure the total amount of fuel consumed by the ship during a specific period. This can be done by monitoring the fuel flow rate or by measuring the quantity of fuel bunkered and the remaining fuel on board.
- Measure the propulsion power output: Determine the power output of the ship’s propulsion system. This can be obtained from the engine’s performance curve or by measuring the shaft power using a dynamometer.
- Convert units: Ensure that the units of fuel consumption and power output are compatible. If necessary, convert fuel consumption to a common unit, such as kilograms or metric tons, and power output to kilowatts (kW).
- Calculate SFC: Divide the total fuel consumption by the propulsion power output. The resulting value will represent the specific fuel consumption.
SFC = Fuel Consumption / Power Output
- Normalize the SFC: To compare the SFC values between different ships or different operating conditions, it is common to normalize the SFC. This can be done by dividing the SFC by the vessel’s deadweight tonnage (DWT) or gross tonnage (GT).
Normalized SFC = SFC / DWT or GT
Note: The specific fuel consumption can be calculated for a specific voyage or a defined period. To obtain more accurate results, it is advisable to collect data over a representative duration of operation and under typical operating conditions.
Remember that the above steps provide a general approach to calculating specific fuel consumption on merchant ships. The specific method may vary depending on the ship’s configuration and available measurement data. It is recommended to consult the ship’s technical documentation or consult with experts familiar with the vessel’s systems for more accurate calculations.
Mathematical examples
Sure! Let’s walk through a couple of mathematical examples to calculate specific fuel consumption (SFC) on a merchant ship.
Example 1: Suppose a merchant ship consumes a total of 10 metric tons of fuel during a 24-hour period. The power output of the ship’s propulsion system is measured to be 5,000 kilowatts (kW). The ship’s deadweight tonnage (DWT) is 20,000 metric tons.
Step 1: Determine the total fuel consumption: The ship consumed 10 metric tons of fuel.
Step 2: Measure the propulsion power output: The power output is measured to be 5,000 kW.
Step 3: Convert units: No conversion is required in this example.
Step 4: Calculate SFC: Divide the total fuel consumption by the power output. SFC = 10 metric tons / 5,000 kW = 0.002 metric tons/kW
Step 5: Normalize the SFC: Divide the SFC by the DWT. Normalized SFC = 0.002 metric tons/kW / 20,000 metric tons = 1 x 10^-7 metric tons/kW/ton
Example 2: Let’s consider another example with different values. Suppose a merchant ship consumes a total of 150,000 kilograms of fuel during a 48-hour period. The power output of the ship’s propulsion system is measured to be 8,000 kilowatts (kW). The ship’s gross tonnage (GT) is 30,000 gross tons.
Step 1: Determine the total fuel consumption: The ship consumed 150,000 kilograms of fuel.
Step 2: Measure the propulsion power output: The power output is measured to be 8,000 kW.
Step 3: Convert units: Convert the fuel consumption to metric tons. Fuel consumption = 150,000 kilograms / 1,000 = 150 metric tons.
Step 4: Calculate SFC: Divide the total fuel consumption by the power output. SFC = 150 metric tons / 8,000 kW = 0.01875 metric tons/kW
Step 5: Normalize the SFC: Divide the SFC by the GT. Normalized SFC = 0.01875 metric tons/kW / 30,000 gross tons = 6.25 x 10^-7 metric tons/kW/ton
These examples demonstrate the calculation of specific fuel consumption on merchant ships based on given fuel consumption, power output, and vessel tonnage. Remember to adjust the units and consider any normalization factors based on the specific requirements or industry standards.
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