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Combinator optimizing

For controllable pitch propeller an operational measure is to run the system using a “combinator curve” with optimized pitch settings and propeller speed, making it possible to operate the total propulsion system with optimum efficiency.

Applicability and assumptions

Combinator optimizing is applicable for vessels with controllable pitch (CP) propeller regardless of ship type and age.

Combinator curves takes into account engine requirements, propulsion efficiency, cavitation patterns in different conditions and the operational profile of the vessel. The curves are applied for improving the propulsive performance for vessels with (CP) propellers.

The following points are procedures for improving the propulsive performance by applying combinator curves:

  • Evaluate the current combinator curves and make sure that curves for different operational modes exist, especially relevant for vessels with large variations in propeller loading.
  • Run simulations and develop new curves if one has any reason to believe that the existing curves are not optimized for relevant operations
  • Make sure that the optimum combinator curves always are used
  • Evaluate and document the effect of optimal usage of combinator curves
  • Train crew on expected ship speed and thrust relation

Cost of implementation

There is a small cost associated with the installation of the measure to $1,000 – $1,500 (USD).

Reduction potential

The savings potential is largely dependent by the initial propeller operation, and also how suitable the operational profile is to the vessel. A controllable pitch propeller will be beneficial for operational profiles with a need for both low speed – high thrust and high speed – moderate thrust. For vessels with shaft generators however, there will be limitations on how low the main engine RPM can be before auxiliary power production drops out. Here, it may be appropriate to consider increased use of auxiliary machinery for electricity production.

In summary, there will be large variations in the reduction potential with anything from 0.2 – 3% of the total fuel consumption.

Other References

  1. The ship power supplier / Technology guidelines for efficient design and operation of ship propulsors
  2. Air pollution and energy efficiency study series / Study on the optimization of energy consumptions as part of implementation of a ship energy efficiency plan (SEEMP)
  3. 3) Geertsma, R.D., et al., 2017. Design and control of hybrid power and propulsion systems for smart ships: A review of developments.

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