Specific fuel oil consumption is the measure of the mass of fuel consumed per unit time to produce per KW. The marine engine efficiency is usually determined using the SFOC.
In order to achieve accuracy, the fuel consumption and power developed is always measured over a suitable time period on a good weather. The formula used for calculating SFOC is:
SFOC (g/kwh) = Mass of fuel consumed per hour / Power developed in KW
Engine Characteristic Curve: Power(BHP) – Speed Curve
Typical Fuel oil consumption of marine engines to as low as 163 gm/KWH
The readings of the flow meter to the main engine should be noted over the specified time interval say 1 hour. With the difference in readings, the volume of fuel consumed is obtained. It can also be measured by noting down the HFO service tank reading provided the oil is being supplied only to the main engine.
The mass of the observed volume of fuel consumed can be determined by following the above-said bunker calculation procedure.
The * Horsepower* can be measured using dynamometer if fitted on the shaft of the engine which will indicate the BHP in the digital indicator. If not, the horsepower can also be calculated using engine rpm and average pump fuel index with the aid of engine characteristic curve of various sea trials which is supplied by the manufacturer. However, the calorific value of the fuel used for sea trial may differ and hence compensation factor has to be determined to obtain the accuracy in calculation.
Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output. It is the rate of fuel consumption divided by the power produced.
Commonly BSFC is expressed in units of grams per kilowatt-hour (g/(kW⋅h)). The conversion factor is as follows: BSFC [g/(kW⋅h)] = BSFC [g/J] × (3.6 × 106)