MARITIME – PROPULION & PERFORMANCE CALCULATOR
Fuel Economy Speed Curve
A precise tool.
What is the Fuel Economy Speed Curve & How does it work?
The fuel consumption of a vessel is not a linear function of speed. As speed increases, the hydrodynamic resistance grows roughly with the square of the velocity, while the power required grows with the cube. Consequently, the amount of fuel burned per nautical mile first decreases, reaches a minimum, and then rises sharply at higher speeds. By plotting fuel per distance against speed, operators can identify the βoptimum speedβ β the point where the vessel achieves the lowest fuel cost for a given voyage. This speed balances the tradeβoff between longer travel time and higher fuel burn, and is a key metric for economical voyage planning. The underlying physics can be expressed with a simple analytical model. The resistance of the hull is approximated as R = Β½β―Οβ―C_Tβ―Aβ―VΒ², where Ο is water density, C_T a total resistance coefficient, A the wetted surface area, and V the ship speed. The required shaft power is P = Rβ―Β·β―V, and the fuel flow follows from the specific fuel consumption (SFC) and propeller efficiency (Ξ·). Combining these relations yields a compact expression for fuel per nautical mile.
F_{NM}=frac{rho,C_T,A,V^{2},text{SFC}}{2,eta,1000}
F_{NM} = fuel consumption per nautical mile (kg/NM)
Parameters
Result
β
Frequently Asked Questions
What is the purpose of a fuel economy speed curve?
A fuel economy speed curve helps identify the optimal speed at which a vessel can travel with the lowest fuel consumption per nautical mile.
How does hydrodynamic resistance affect fuel consumption?
As speed increases, hydrodynamic resistance grows roughly with the square of the velocity, leading to higher fuel consumption at faster speeds.
Why is power required to grow with the cube of velocity?
Power required grows with the cube of velocity because overcoming increased resistance demands more energy as speed increases.
What does the 'optimum speed' refer to in this context?
The optimum speed is the point where the vessel achieves the lowest fuel cost for a given distance traveled.
How can operators use this calculator effectively?
Operators should input their vessel's specifications and operating conditions to plot the fuel consumption curve and determine the most economical speed.
What factors can influence the shape of the fuel economy curve?
Factors such as hull design, engine efficiency, sea state, and cargo load can all affect the shape of the fuel economy curve.
Is this calculator suitable for any type of vessel?
While it's generally applicable, specific adjustments may be needed for unique vessel types or operating environments.
Results are for informational purposes only and do not constitute professional advice.