Abstract
The costs and the engineering problems of the mechanism of any controllable pitch propeller are strongly dependent on the magnitude of the blade spindle torque. The blade spindle torque can be split into three parts: a hydrodynamic torque, a friction torque and an inertia torque due to the centrifugal force.
The paper discusses the possibility of minimizing the hydrodynamic blade spindle torque by means of ventilation through holes on the face of the blade. The influence of the ventilation on the blade spindle torque is analysed by means of extended computer calculations.
The two dimensional pressure distribution of the ventilated sections is calculated with a linearized theory for lifting foils at zero cavitation number [9]. Blockage and interference effects in the ventilated condition are neglected.
The distortion of the mean lines due to pitch setting is taken into account. The induced velocities by the free vortex system are calculated with a special lifting line theory, which has been adapted to heavy loadings by means of some empirical factors.
As an example an existing c.p.p. of a trawler is analysed. It is concluded that ventilation is a promising tool for the realisation of c.p.p. designs with low blade spindle torque.
Get full access to this article
View all access options for this article.