Hydrodynamic Analysis And Optimal Matching Of Propeller And PBCF Based On CFD

With the emergence of global environmental issues,energy-saving and emission-reduction technologies are becoming more and more important,and the shipbuilding industry is facing severe challenges as a high-energy-consuming industry.As an important device for ship propulsion and as one of the main energy consumption of ship’s equipment,the propeller performance is highly significant for reducing energy consumption and improving the energy-saving effect of ships.How to improve the performance of propellers has become an important topic of current research.For the purpose of improving the performance of the propeller studied in this paper,the propeller boss cap fin(PBCF)is added to solve the optimal fin parameters.The three-dimensional models of propeller and PBCF are obtained by combining the theory of forward-backward modeling with the software of Geomagic Design X,Geomagic Qualify and UG.The appropriate calculation domain and meshing scheme are established for the propeller studied.The boundary conditions are set by CFX software to solve the performance of the propeller and to analyze the performance change rule,pressure distribution and flow field change.Based on the optimization design theory,the optimization mathematical model is established by viewing the installation angle,radius and axial distance of the fin as design variables,the maximum thrust coefficient and efficiency of propeller as objectives,the range of design variables as constrains.With the help of Workbench response surface optimization module and the design points obtained by BBD method,the response surface model is established.On this basis,genetic algorithm is selected to solve the optimal value and the range of design variables.Through the analysis,the following conclusions are drawn:(1)With the increase of the advance coefficient,the propeller thrust coefficient and torque coefficient decrease gradually,and the efficiency increases firstly and then decreases.(2)After finning,thrust coefficient increases at low speed,torque coefficient decreases obviously,maximum gain is 3.851%,but efficiency gain decreases at high speed.Generally speaking,efficiency gains are between 2% and 4%,efficiency gains are larger at low speed and heavy load or with larger hub vortices,and performance improvements are more obvious.(3)The fin improves the efficiency of the propeller by producing negative torque and reducing the torque required for the whole propeller rotation.The fin increases the overall thrust of propeller and improves efficiency through dispersing and weakening hub vortices and increasing the back pressure of hub.(4)The installation angle of the design variable is the most important factor,while the radius and the axial distance have less influence.(5)Response surface shows the variation between variables and objectives.(6)The multi-objective optimization method based on response surface was used to obtain the desired optimization scheme: radius r/R 0.26,axial distance 71 mm,installation angle 68°.In this paper,the propeller and PBCF are obtained by combining forward and backward modeling,which provides a feasible scheme for the establishment of similar models.Using CFD method to solve propeller performance is not only accurate and convenient,but also can obtain abundant simulation results,which is of great significance to the study of propeller performance.Based on response surface genetic algorithm,a method of solving the optimal parameters of PBCF is proposed,which provides a research idea for the design of PBCF.In general,the matching relationship between propeller and PBCF device can significantly improve the performance of propeller and reduce ship energy consumption.