Study On The Hydrodynamic Performance Of Shaftless Rim Thruster With Appendage

In recent years,there is no shaft rim propeller(a kind of integrated electric propulsion device,Shaftless Rim-Driven Thruster,referred to as "without shaft RDT,note: this article without shaft rim propeller in shaft RDT)is developing rapidly,its for ships and submarines in the power system advanced and novel electric propulsion system.Shaftless RDT is different from the traditional propeller structure.It gives up the traditional shafting drive in structure,connects the blade directly with the circumferential driving ring(rim),and drives by motor.It has the advantages of high power density utilization rate,green energy saving and environmental protection,and has become a research hotspot of major scientific research institutes in the world.Although shaftless RDT without shafting and hub greatly increases the inlet flow,the hub of traditional propeller often has the function of rectification and diversion,so tip vortex is easily generated in the axial center of RDT,and tip vortex agglomeration effect greatly affects the hydrodynamic performance.On this basis,a new type of propeller front attachment with asymmetric prerotating stator,central hollow conduit,tip vortex cancellation device and semicircular conduit piece is designed to control tip vortex and reduce energy dissipation of axial RDT rotational wake.The main research contents are as follows:Numerical study on open water performance of shaftless RDT-new propeller front attachment assembly.The open water performance simulation of shaftless RDT was carried out,and the coincidence of the calculated thrust coefficient,torque coefficient and propulsion efficiency was compared with the numerical calculation curves of other scholars,so as to ensure the accuracy of the numerical simulation method in this thesis.Using the international ITTC standard,three grids of different basic sizes were set up to carry out grid independence analysis,which further verified and ensured the accuracy of the numerical simulation in this thesis.The propulsion efficiency of the axisless RDT-new propeller front attachment assembly was calculated and compared with the propulsion efficiency of the axisless RDT without attachment.The numerical changes of the thrust coefficient,torque coefficient and propulsion efficiency before and after installing the new propeller front attachment were analyzed,and the energy-saving effect of the new propeller front attachment was obtained.Numerical study on variable parameter open water performance of shaftless RDT-new propeller front appendage assembly.By changing the Angle of attack of the asymmetric prerotated stator,the relative Angle of the asymmetric prerotated stator,and the different installation distance between the new propeller front attachment and the shafeless propeller rim,the open water performance of the assembly was calculated,and the thrust coefficient,torque coefficient and propulsion efficiency were obtained.(Note: The method of control variables is adopted,that is,each variable parameter is studied on the basis of the design of the relatively optimal propulsive efficiency of the last variable parameter.)The influence of the change of each structural parameter of the new propeller front attachment on the propulsion efficiency of the axisless RDT-new propeller front attachment combination was analyzed,and finally the new propeller front attachment with the best energy saving effect was designed.Study on hydrodynamic performance of ship-shaftless RDT-new propeller front appendage.The grid-independent verification of bare ship’s drag was carried out,and the ship’s drag value and wave wake under various working conditions were obtained through simulation calculation.The numerical simulation results were compared with the test values to ensure the accuracy of the grid calculation of drag calculation in this thesis and the subsequent self-propelled simulation.A drag simulation study was carried out on the ship model equipped with the vessel and the new propeller front attachment,and the influence of the new propeller front attachment on the hull drag increase,wave wake and axial velocity of the axial section near the propeller disk was analyzed.The ship-shaftless RDT coupling body and ship-shaftless RDT-new propeller front attachment coupling body were respectively carried out self-propelled simulation,and the changes of rotational speed,thrust and torque of shaftless propeller after installing the new propeller front attachment were compared,so as to comprehensively evaluate the energy-saving efficiency of the new propeller front attachment under self-propelled state.