A Study On Energy Saving Of The Propeller Boss Cap Fins With Parameter Optimisation

In recent years,with the proposal of "Green Ship" concept.economic pressure and regulatory requirements make people enhance great interest in improving the propulsion performance of ships.At present,the method of installing energy-saving appendages is widely used to improve the propeller's propulsion performance.Installing propeller boss cap fin is one of the effective methods.The parameters's design of propeller boss cap fins has great influence on its performance,so it is great signifincance into optimizing the parameters of propeller boss cap fin.At the same time,the study on the effect of boss cap fins can not only be judged completely from the open water performance,but also judged through considering the influence of rudder and hull on propeller performance.Firstly,numerical simulation is carried out on the model KP505 and KCS.By comparing the numerical simulation results with the experimental results,it is found that the calculation errors are less than 5%,which satisfies the accuracy requirements of numerical calculation.Three sets of grid methods are used to verify the irrelevance of the grid.The feasibility and accuracy of the numerical calculation method are verified from the aspects of open water performance,resistance,the waves and wake fields.At the same time,the calculation and meshing method are verified.The mechanism of propeller boss cap fins is studied by model test and numerical simulation.The flow field characteristics of the boss cap fins are thoroughly analyzed,and meanwhile the effect of the boss cap fins is better understood.The mechanical characteristics,flow field characteristics and anti-vortex mechanism of the propeller before and after installation of the hub-cap fin are analyzed.Based on the study of its mechanism,the influence of the variation of propeller parameters on the open water performance of propeller is further studied.The parameters of fin height,installation angle,fin length and installation phase difference are mainly studied.It is found that the existence of boss cap fins of propeller has great influence on the axial,radial and tangential velocity behind the propeller,and the effect of axial velocity is relatively the largest one.The height of fin has the most obvious influence on the performance of the propeller,and even has adverse effects when its height is too large.The selection of installation phase difference mainly depends on the rotation direction of the propeller root vortices.The installation angle should be chosen near the angle of the propeller blade root.The study of propeller boss fins is not enough for the propeller open water performance.On the basis of parameter optimization,the performance of rudder fin and ship's propeller fin system is studied,and the effects of rudder installation position and hull itself on boss cap fins action are studied respectively.It is found that the existence of rudder will reduce the effect of boss cap fin relatively.Installation of boss cap fin has little effect on hull resistance,but can increase the thrust and reduce the torque,the energy-saving effect is obvious.