Ship operators with a fixed regular trade face the
possibility to reduce operating costs, if the ship is
designed for the requested route. The optimisation of the
propulsion concept for a predefined service then offers the
possibility to reduce the fuel consumption compared to
other vessels on the same trade significantly.
In order to optimise the performance of a propulsion
concept for a specified operational spectrum, it isnecessary to predict the performance of the propulsion
system over the whole variety of operational conditions.
RoRo- and RoPax-vessels are often equipped with dieselmechanic
propulsion and Controllable Pitch Propellers
(CPP), giving the vessel the ability for autonomous
manoeuvring without tug assistance. Especially in shortsea
shipping, this is a widely preferred solution.
However, the ability to control the propeller thrust by
pitch setting is also used to control the vessel’s speed in
sea mode. A shaft generator is then used to generate the
ship’s electrical power, making it possible to switch off at
least one of the auxiliary engines.
In order to assess the efficiency of such an operation, it is
necessary to predict the performance of all components,
including the behaviour of a CP-propeller with pitch
settings different from the design pitch as well as, e.g., the
fuel consumption of the main engines.
The performance of the rudder in a propeller slipstream
during off-design operation is then also of interest for the
assessment of course-keeping and manoeuvring
capabilities.
A focus of the present paper is on the development of
tools for the hydrodynamic estimation of propulsors and
manoeuvring devices in off-design conditions and their
practical use in ship design. A further aspect is the
interaction with the prime movers, making it possible to
assess a propulsion concept as a whole with respect to the
total operating costs.