In recent years, the requirements for marine propeller by our customers have been diversified with remarkable manifold due to the general inclination for higher ship speed, the energy-saving oriented, and for the improvement of comfortableness aboard.

 The performance required of propeller consists of largely two elements, one is "Higher efficiency" and the other is "Reduction of exciting force".

 Speaking of propeller performance, not only the propulsive efficiency but also the reduction of cavitation and hull exciting force, as well as propeller strength etc. are important themes. At our company to meet these requirements, the PD program (Pressure Distribution Oriented Propeller Design System) was introduced, developed under collaboration with Ship Research Centre of Japan (SRC). With this new PD program, it is possible that the propeller blade section is automatically designed with the pressure distribution preferable for the flow over the blade surface, destining the propeller performance, to be given first. At the same time we can calculate cavitation pattern, blade fatigue strength and hull exciting force. At the next stage, SF999 was introduced for the prediction of propeller exciting force. This program, which is based on neural network algorithm, can drastically improve the accuracy of the prediction of the hull exciting force.

 At the third stage, SQCM (Simple Surface Panel Method) was introduced for the prediction of the propeller performance including the influence of the blade thickness, rake and propeller hub.

 With these new programs, it was made easier for us to make finer designings promptly in order to reply to our customers' diversified requirements, in addition to the remarkable improvement of efficiency for the development of new higher-performance blade sections. Fig.1 shows the system of the PD propeller designing computer program. Fig.2 shows an example of simulated cavitation estimations by the PD system (PAI propeller), and Fig.3 shows an example of highly skewed propeller's strength analysis by means of finite element method (I-DEAS).

 Our most advanced propeller designing system has so far produced two types of high-performance propellers. They are high-performance propeller with smaller blade area ratio (PAI propeller) (Photo.1), and highly skewed propeller (HSP) for the main purpose of reducing propeller exciting force for lower vibration (Photo.2).