| The propeller works in the stern flow field,directly affected by the wake,which makes the actual efficiency of the propeller different from the open water efficiency of the propeller.The high wake region above the upper part of the internal of propeller disk and small area near the center of the circle radius of propeller disk for conventional ships.The existence of high flow zone directly leads to the decrease of propulsion efficiency,the deterioration of cavitation performance and the improvement of exciting force.Therefore,it is meaningful to add energy-saving sector duct between hull and propeller to improve the flow field in front of propeller.The hydrodynamic performance of self propulsion and bare ship of KCS ship model was calculated based on CFD method,and compared with the experimental results,verify the feasibility of this method.And the resistance,free surface and the flow field are described,so the subsequent numerical calculation work can be provided reasonable support.In order to analysis energy-saving effect and the energy saving principle of sector duct,first,the hydrodynamic performance of bare boat were calculated without or with the sector duct at different speeds using STAR-CCM+,and analyzes flow field flow of propeller disk wake whether have sector duct after the ship,found sector duct can increase flow of propeller disk.And the flow of the propeller disk tend to be more uniform,the rotation direction of flow different form the rotation direction of propeller due to guide vane,so increase the relative rotational speed of propeller blade relative to the fluid.Then the hydrodynamic performance of hull propeller with sector duct was calculated,the energy-saving effect is obtained in the design of speed sector duct was 3.69%.And flow,axial velocity and tangential velocity distribution of the ship propeller disk is analyzed,further discusses the energy saving principle of sector duct.Finally,the analysis of the hydrodynamic performance of hull propeller with sector duct with variable parameters,by changing single parameters of the combination system(diameter,and relative position of propeller and internal longitudinal axis angle of blade relative to hull),then compared to the original system(the hydrodynamic performance of propeller thrust,torque and the resistance of the hull),found the hydrodynamic performance of hull propeller most favorable when sector duct 0.135D off the propeller and the radius is 0.85R of sector duct,at the same time,with the increase of the medial guide vane angle of attack,the effect of prerotation of sector duct becomes better,the efficiency of the propeller is increased.In order to analyze the influence of hydrodynamic performance of propeller with sector duct after the ship in waves,self propulsion of ship are calculated under the condition of wave,the numerical analysis showed that the sector duct of ship increasing ship resistance in waves,at the same time as due to the sector duct exists,the ship propeller thrust and torque have a certain degree of increase or reduced,and by comparing the wave hydrodynamic performance and changes around the ship hull flow distribution with or without sector duct,found sector duct cases can still improve the ship flow in wave. |
