Enhanced Cycloidal Propulsion

Voith Sch i f f stech ni k G m bH & Co.K G H ei enh ei d m Enhanced Cycloidal Propulsion Dr. Dirk Jürgens[a], Torsten Moltrecht[b] The vertical axis cycloidal or VOITH SCHNEIDER Propeller (VSP) has by no means reached the limits of it’ development. A new generation of VSP with enhanced s hydrodynamics and improved construction is ready for introduction into the workboat market. With the latest computational fluid dynamic methods (CFD) continuously the hydrodynamic is improved. New blade profiles with higher efficiency have been developed. Additionally to the propeller the hull-design of ships with VSP is subject of continuos research and improvement. A new guard and nozzle plate has been developed for VSP propelled tug boats. An new propeller generation with higher maximum input powers are under development. For the redesign of each component an industry-leading structural analysis FEM program is used. This provides the power of linear and nonlinear structural capabilities to deliver reliable structural simulation results. New construction principles for key-components as blades and main bearing have been developed. The first shipset VSPs with 6 blades (instead 5) and improved hydrodynamic efficiency is already installed and has been tested during trial runs in July 2002 successfully. A further good example of enhanced cycloidal propulsion is the VOITH CYCLOIDAL Rudder (VCR). This modified VSP, with only 2 blades, is the latest propulsion and maneuvering device to be adopted for ocean-going vessels at higher speeds. It has two operating modes: a passive one, in which the VCR acts as a conventional rudder for cruising speed and an active one, in which it works in the same way as a VSP to ensure a high degree of maneuverability at slow speeds. bird’ wing action, which also produce simultaneous s 1. HYDRODYNAMIC PRINCIPLE OF thrust and steering forces. Animals with such CYCLOIDAL PROPULSION movements have the optimal adaptation to their living environment. On a VSP the blades project below the ship's hull and rotate on a rotor casing about a vertical axis, having an oscillatory motion about its own axis superimposed on this uniform rotation. The blade’ oscillating s movement determines the magnitude of thrust through variation of the amplitude (pitch), the phase correlation determines the thrust direction between 0 and 360 degrees. Therefore an identical thrust can be generated d:\tm\winword\tm463_workboat2002.doc in any direction. Both variables - thrust magnitude and Fig. 1: Cycloidal path of VSP blade with hydrodynamic lift thrust direction - are controlled by the hydraulically The idea of this unique propulsion and maneuvering activated kinematics of the propeller, with a minimum system was born by the Austrian engineer Ernst of power consumption. Schneider in 1926 [1]. The principle of thrust Consideration of the processes on each blade during one generation by a VSP is comparable to a fish’ fin or a s [a] Head of Research and Development Dep., VOITH Schiffstechnik GmbH & Co. KG, Heidenheim, Germany [b] Naval Architect, SNAME, VOITH Schiffstechnik GmbH & Co. KG, Heidenheim, Germany Voith Sch i f f stech ni k G m bH & Co.K G H ei enh ei d m revolution provides the simplest explanation of the eccentrically and connected to the crank, which pivots resultant hydrodynamic forces. By superimposing the around the bearing pin fitted to the rotor casing. A rotary movement of the rotor casing on a straight line connecting rod transfers this movement to the blade perpendicular to the rotational axis (to represent the through the blade-actuating lever. (Fig. 2) movement of the vessel), the blade of the VSP follows a The rotor casing of a VSP carries 4, 5 and nowadays 6 cycloid (Fig. 1). To generate thrust the blade profile has blades around it’ circumference.