Ships propeller propulsion

Calculating the optimal operating parameters of the inland ship s propulsion system, requires performing many intermediate calculations. At each of the steps, accuracy of the calculations is correlated with the rounding precision, but also with the accuracy of the characteristics and the geometry of the propeller. For this reason, one notes the impact of these errors on the final results. (Eloot Vantorre, 2011). 

Propellers are the predominant propulsive devices driving ships, although water jets are now used in some high-speed ships. An experimental installation in a small ship of a magnetohydrodynamic propulsor has been tested, but it achieved rather low propulsive efficiency. Fish-like propulsion also has been examined for possible application to ships and underwater vehicles. 

Resistance and Stability. As a ship moves through the water, it must push aside the water ahead of it. This water moves away from the ship as waves. Water flowing along the sides of the ship exerts a friction force on the hull. The combination of these forces is called the resistance. The propulsion force provided by a ship s propeller must overcome the resistance. Naval architects can accurately predict the friction resistance, but the resistance associated with pushing the water aside is usually determined by testing a scale model. 

Systems for low- or medium-speed diesel engines used as gendrive or for propulsion of ships with fixed propellers often work with look-up tables or a characteristic curve as input for an open-loop reductant dosing control (Fig. 2.31). As the engines only use a small band within the engine map (Fig. 2.32) the NOx-emission and thus the reductant dosing rate has a fixed correlation to either engine speed or load. 

Fig. 2.32 Diesel engines used as gendrive or for propulsion ships with a fixed propeller use only a narrow band within the engine map. This enables the use of lookup tables for reductant dosing control...

Figure 7 shows the propulsion characteristics of ship with the Ka4-55 propeller in the nozzle 19A. On the graph curves corresponding to the values of errors resulting from the implementation of the propeller diameter of 3% accuracy were plotted... 

Figure 7. Propulsion characteristics of ship with the Ka4i55 propeller, with the accuracy of propellers diameter dDID = 3%.

For propeller driven ships, there are limits of applied main propulsion power usually assumed as 25% of full power in dependence on the type of seabed protection (Abramowicz-Gerigk. Burciu, 2011). 

This is mainly caused by the introduction of Ultra Large, high powered Container Ships (ULCS) over 8,000 TEU (Twenty feet Equal Unit), of 300-400 m length, equipped with 2000-3500 kW thrusters and 60-80 MW propulsion systems (Hermans Degens, 2011). They can perform manoeuvres in very tight areas and strong weather conditions, up to port operational limits, using their thrusters and propellers to increase efficiency of manoeuvres assisted by tug boats. 

It was the development of the nuclear reactor for navy propulsion that led to the use of zirconium and zirconium alloys as a fuel cladding material. This program, headed by Captain, and eventually Admiral, Rickover demonstrated flie viability of using fission energy to propel navy ships and submarines. 

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