Fuel consumption

[Henrik]

Hi

Do anyone know how the ships fuel consumption is calculated - i have been searching all over the web to find a suitable formulae, but so far i have come up utterly empty handed.

Maybe RDK would be so kind to help ?

Thank you in advance

[Pipit]

Fuel consumption would be based upon the required amount of fuel to generate a specific amount of power--ie: How much fuel does it take for the engines to develop a kW/Hour (basically, same method of determining fuel consumption for any fuel powered motor).

If an engine rated at 50,000kW requires 150g of fuel to produce 1kWh, then for that ship traveling at full power, that engine would thus require 7,500,000 grams (or, 8.27 short tons) of fuel per hour.

Of course, each engine is different in its fuel demands, so 150g/kWh is not a standard but an example.

So, to calculate the route fuel consumption (how much fuel per day a ship will use while traveling between two points), at its simplest, you will need to know fuel consumption per kWhour at its travel speed (ie: 50,000kWh to travel 20knots at 150g/kWhour) and how far it is traveling. So, a ship with the above stats would use 1,240.5tons of fuel traveling 3000 nautical miles.

Factors such as type of engine (how well it is maintained, how efficient is it at producing energy, its maximum designed energy output verses current energy demand), fuel additives, temperature of fuel (colder fuel=greater density of fuel, harder ignition/burning, less fuel efficiency), temperature of air (colder air means more work to produce energy), size of ship (heavier ship, more energy required to more it), length-to-width ratio of ship (longer ship, finer hull lines, allows more speed than a shorter, wider ship of same displacement), draught/draft of ship (affects speed, stability, etc), temperature of water/fresh verse salt water (colder water is denser, affects buoyancy/draught of ship), wind direction and speed, ocean currents, design of propellors, etc. all affect the fuel consumption rate on a ship, making hourly calculations on fuel consumption an ongoing matter if one if calculating based upon maintained speed and not maintained energy output.

Hope it gives a bit of a start.... (and hope it doesn't lead to a headache)...


(hmmm... maybe math class did pay off, otherwise I would have never read that article on small engines and fuel consumption)

[Nerby]

[Henrik]

@Nerby

Thank you for the link

Even though the math is (quite) a bit over my head i still found it rather interesting.

As a side remark i have also been wondering about how they calculate the decrease in top speed when a ship is fully loaded ? !

[Nerby]

Hello Henrik, it's a pleasure to help.

About max speed reduction, I can only tell you that it is a maximum 5% reduction. A few experiments should be run to understand:

- when the decrement starts and at which rate;
- if fuel consumption is similarly increased;
- what happens when ship is overloaded.

Best regards,

Nerby

[Christian Todt]

What du you need the consumption for?

If you want to find out, if a freight is profitable,
i can provide you a excelsheet that does that.
I made it some time ago and given you like to calculate rathe than
follow rules of thumb it is quite useful.

Best Regards,
Christian Todt
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