Hydrodynamic Characteristic Of Full-revolving Controllable Pitch Ducted Propeller And Fine Analysisof Flow Field

There are various resources in china,including marine fishery,natural gas,oil and vast land.The utilization of oceans has been slowly transformed from marine transportation to developing the marine resource,which sets a higher requirement for the performance of ship,offshore platform and semi submersible platform that includes its own navigation,operation,dynamic positioning and so on.The pros and cons of propulsion and control performance of all-direction propeller have put greater impact on the ship for turning,horizontal movement,emergency stop,reverse,towing.Analysis of hydrodynamic characteristics and fine flow field to full-revolving controllable pitch ducted propeller are of great significance to improve the propulsion and maneuverability of the ship.In this paper,full scale of full-revolving controllable pitch ducted propeller has been simulated based on the Fine-Marine software.Ducted propeller,which is in open water and working at the stern in all direction,as well as the hydrodynamic characteristics and fine flow field in different pitch ratio,has been considered.Research and analysis of the main results are as follows:(1)The No.19A+Ka series of propeller,which is mature and comprehensive in the hydrodynamic performance,has been examined.At the same velocity coefficient,the calculation results are compared with the experimental results.The average error is 2.342% and the maximum error is 4.3%,not more than 5%,which is in the range of allowable error.So the calculation model and method in this paper is feasible.(2)The calculation model of full-revolving controllable pitch ducted propeller has been established and hydrodynamic performance of full-revolving controllable pitch ducted propeller has been evaluated with fuzzy comprehensive evaluation method on the pitch ratio 1.0.Gaps of blade tip are respectively 6mm,10 mm,14mm and 18 mm.Considering the four main factors,which include total propulsive efficiency,total thrust coefficient and thrust coefficient of pipe and manufacturing,gaps of blade tip whose best value C=14mm is selected.(3)In this paper,prediction of hydrodynamic performance of full-revolving controllable pitch ducted propeller is conducted under the condition of open water.Within the range of advance coefficient,hydrodynamic characteristics of controllable pitch ducted propeller with different pitch ratios have similar distribution tendency.The maximum of hydrodynamic characteristics increase at a rapid speed,following the increase of pitch ratio.This paper analyzes distribution of disk pressure and velocity for propellers with different pitch radios.With increasing advance coefficient,the pressure of face of blade decreases and the pressure of back of blade also decreases.Face of blade's velocity lines are mainly concentrated on blade tip,which are gradually in diffusion along the blade.Back f blade's velocity lines are mainly concentrated on the margin of blade,which gradually spread out.With the same pitch ratio,the larger the advance coefficients are,the more evenly the back of blade's velocity lines are distributed.(4)This paper examines and analyzes hydrodynamic performance of controllable pitch ducted propeller behind ship.Ship resistance has regular fluctuations from P/D=0.6 to P/D=1.4,and its amplitude of fluctuation gradually smooth as well as basically remain stable at 4s.When P/D=1.4,duct propeller thrust value reaches the maximum.The propeller thrust coefficient,ducted propeller thrust coefficient,torque coefficient are greater than the calculated value of simulation in the open water.Under the influence of ship wake,catheter after ship propeller thrust growth are greater than the hull resistance value.In the meanwhile,fine analysis flow field of each disk between open water and stern are calculated.Velocity distribution is similar,but speed of different disk sections is much larger than that in open water,and the phenomenon is especially obvious near the blade and the blade tip position.(5)The study of hydrodynamic performance of full-revolving controllable pitch ducted propeller behind ship selects pitch ratio of 1.0 and calculate hydrodynamic performance when propeller has 30°,60°,90° deflection angle.When the full-revolving controllable pitch ducted propeller behind ship at 30° deflection,hydrodynamic numerical value change rule is similar with numerical values in open water and the situation when propeller has no deflection.When the full-revolving controllable pitch ducted propeller behind ship at 60° and 90° deflection in high speed zone,propeller thrust coefficient,screw torque coefficient,catheter thrust coefficient are different from decreases with the increase of advance coefficient change trend.As the controllable pitch ducted propeller behind ship deflection angle becomes larger,hydrodynamic coefficients are on the rise.When the full-revolving controllable pitch ducted propeller behind ship at 90° deflection,compared with the total thrust coefficient when the 30° deflection in different speed coefficient,is 1.61% ~ 92.7% larger.