Research On Parametric Modeling Method And Optimization Design Of Marine Propelle

In recent years,rim-driven thrusters have been gradually applied as a new type of high-efficiency propeller thruster,which uses hubless propellers that have higher open water efficiency than traditional propellers.Many scholars have conducted in-depth research on it.In order to further design and optimize it,this paper develops a parametric modeling system for hubless propellers and traditional propellers,which realizes the automation of propeller modeling.Based on this system and computational fluid dynamics(CFD)method,this paper designs and optimizes a hubless propeller with inverse thickness law,and further designs and applies the inverse thickness propeller propulsion system.The main research contents of this paper are as follows:First,the propeller parametric modeling system was studied.Based on the chart method,a calculation model of two-dimensional and three-dimensional shape points of the chart propeller was constructed,and the model was modified to make it suitable for free-shape propellers including hubless propellers.According to the constructed model,a propeller shape point calculation software was developed using MATLAB,which realized the shape point calculation function of two kinds of chart propellers and custom parameter propellers.Then,NX was secondarily developed to realize the function of automatically modeling traditional propellers and hubless propellers according to input parameters and shape point data.The hydrodynamic performance of the chart propeller with parametric modeling was analyzed by using CFD method,and the correctness of the modeling system was verified.The JQ-5-81 series propeller was parametrically modeled and its hydrodynamic performance was analyzed by using CFD technology.The results show that the open water performance of the propeller is consistent with the chart data and meets the design requirements.By analyzing the pressure distribution,wake velocity distribution and vortex characteristics of the propeller,the correctness of the propeller model was further verified,thus proving the reliability of the modeling system.Secondly,based on the computational fluid dynamics method and the parametric modeling system,a hubless propeller with inverse thickness law was optimized and designed.A hubless propeller with inverse thickness law was modeled by using the parametric modeling system referring to the Ka4-70 propeller,and its open water performance was analyzed by CFD technology.The results show that the inverse thickness propeller has certain research significance and application potential.Taking the maximum open water efficiency as the optimization objective,the inverse thickness propeller was optimized by adjusting parameters such as blade section chord length,blade length and pitch ratio,and an average open water efficiency increase of 6.45% was achieved in the maximum efficiency advance speed range.The article also compares the wake field velocity and vorticity distribution of the inverse thickness propeller before and after optimization and the traditional propeller,and analyzes the reasons for the performance difference of different propellers.Finally,the design and application of the inverse thickness propeller propulsion system was carried out.The influence of different duct shapes on the hydrodynamic performance of the propulsion system was analyzed,and the optimal one among the four designed ducts was selected.In view of the problem of low system thrust,a counter-rotating propeller scheme was proposed to increase the thrust.The hydrodynamic performance of the system under different pitch ratios was analyzed,and the optimal pitch ratio counter-rotating propeller system was obtained,which increased the thrust by 55.44%compared with the single propeller system in the maximum open water efficiency range.Finally,the ship-engine-propeller matching was carried out for the system,and the suitable ship resistance and engine power were matched under the maximum efficiency condition.