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Dinu Taraza, Nicolae Buzbuchi, Jean Sever Popovici. Calculation of the Harmonic Structure of Marine Propeller Torque and Thrust. SAE Technical Paper Series 941698, 1994.

Abstract: Among the excitation sources of vibration for the marine propeller shafting, the propeller itself plays a significant role. It is one of the excitation sources for the axial vibrations and a major contributor among the excitation sources for torsional vibrations. Thus, the possibility to predict the harmonic structure of the torque and thrust, in the design stage of the propeller system, has a great importance for the designer. In this direction, the paper presents two computation methods of calculation of the propeller torque and thrust, the first being a semi-analytic one, based upon the wake field diagrams experimentally determined, and the second based on the propeller series diagrams and general empirical formula for the wake and suction coefficients. This second analytical method was presented more detailed, being a possible primary tool for the designer. A vortex model of the marine propeller, based on Prandtl lifting-line theory, has been developed. Considering the system of bounded and free vortices representing the propeller blade and its interaction with the incipient wake generated by hull motion, the velocity field around the blade profile is determined. Based upon a non-dimensional expression of the circulation, as a function of blade radius and angle of rotation, torque and thrust are computed and expressed as Fourier series.
Parallel to the theoretic study, experimental investigation have been carried-out, both in cavitation tunnel and towing tank, showing an acceptable agreement between calculated and measured fluctuations of torque and thrust

Keywords: Propeller, harmonic structure of the torque and thrust

Posted by Nicolae Buzbuchi

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