Study On Matching And Dynamic Performance Of Ducted Propeller

Underwater vehicles are novel robots that can bear thousands of meters deep in water and operate within hundreds of miles radius with quantities of abilities,such as observing,analyzing,etc.The most common vehicles such as Autonomous Underwater Vehicles(AUV),have been applied to scientific research(like flammable ice exploration),military(like mine clearance or surveillance)and civilian fields(like rescues or fishing),and higher demands are imposed upon various aspects of vehicles' performance,like endurance,control,noise,etc.Which are directly related to propulsion system.Therefore,excellent performance of power system is necessary to ensure the relevant technical indicators of vehicles.Currently,the ducted propellers has been widely used on vehicles as propulsion since they are not only more efficient,but can offer more thrust than conventional propellers.Hence,we seek to explore and solve a series of problems encountered when the vehicle is performing its mission by investigating the performance of ducted propeller.Which can provide technical data and reference design for ducted propellers when they are applied to underwater vehicles.This paper take 19A/Ka4-50 ducted propeller as prototype.The Ansys-CFX and Actran softwares are employed,which use the method of solving RANS equation and Lighthill's acoustic analogy respectively,to study the hydrodynamics and noise performance.Detailed research contents are as follows:Firstly,the hydrodynamic performances of various matching parameters(like area ratio and pitch ratio of blade,diameter ratio and length-diameter ratio)limited in a certain range are studied,among which the efficiency is main research content.Also the analysis on flow structure characteristic is conducted.By analyzing the obtained computational data,a new design method for ducted propeller is presented,followed by is a verification on feasibility and accuracy of the proposed method,which can also be used as reference method for other series ducted propellers.Secondly,the dynamic performances of ducted propeller under different working condition with variable speed are studied,the focus is mainly on the hysteresis effect of thrust and other performances due to the action of inertia force produced by variable speed,which varies as sinusoidal curve along with time.The computed unsteady performances in different fluctuate amplitude,frequency and inflow velocity are compared with preceding steady results(or results of uniform motion state),by analyzing the phase difference of performances between two type of state,we come to conclusion that lower frequency and amplitude,higher advanced coefficient will own lower phase difference.Finally,in order to meet the noise index of running-vehicles,the non-cavitating noise of ducted propeller in various matching parameters(length-diameter ratio of duct and pitch ratio of blade)and working condition parameters(frequency and amplitude of rotating speed)is predicted by adopting finite element method.Which can provide relevant technical data for low noise ducted-propeller.In addition,the Noise similarity of different scale and working condition is studied with the reference of cavitating noise similarity,which is proposed in 18 th ITTC.The numerical simulation results indicate the deduced formula that used to describe relationship of acoustic pressure level between different scales or working conditions has some reference significance.