HYDRODYNAMIC MODELLING AND PERFORMANCE EVALUATION OF CYCLING VARYING PITCH PROPELLER IN NON-UNIFORM WAKE FIELD USING OPEN-WATER RANS CFD SIMULATIONS

摘要

The cyclic varying pitch propeller is a controllable pitch propeller that is able to change the pitch of the propeller blades individually during one revolution in order to compensate for the non-uniform wake field. By changing the pitch to compensate for the non-uniform wake field, the unsteady phenomena such as cavitation, vibration and noise can be reduced. This gives new possibilities when designing the propeller blades, which can result in a higher propeller efficiency. In order to make the blade design, the actuation mechanism and determing the optimum blade pitch trajectory, it is necessary to determine the hydro-dynamic loads acting on the propeller blades due to the nonuniform wake field. An unsteady CFD simulation of the cyclic varying pitch propeller in a non-uniform wake field is computational expensive and is not suitable for determining the optimum pitch trajectory in an iterative manner. Hence, it is desired to have a less computational expensive method to calculate the optimum pitch trajectory. A simple method to characterize a propeller is to determine its open-water characteristics. It is therefore reasonable to try using the propellers open-water characteristics to determine the hydrodynamic loads in order to obtain a less computational expensive method. In this paper, the propellers open-water curves are determined for a range of pitch settings through steady state RANS CFD simulations. To avoid making an erroneous conclusion, the uncertainty of the simulation results are determined. The propellers open-water curves are used to evaluate the thrust and efficiency for the cyclic varying pitch propeller which are compared to the controllable pitch propeller.