Research On Composite Energy-saving Attachment Technology Of Ship Propeller Based On Propeller Boss Cap Fins And Pre-duct

For a long time,With the scarcity of resources,the rise of global climate and other issues.The International Maritime Organization’s standards for ocean transportation safety and ship greenhouse gas emissions are further improved.Promote the implementation of ship energy efficiency design index.Make the shipbuilding industry face once again difficulties and challenges.How to improve the propulsion efficiency of ships is favored by global design institutes and shipyards.The propeller energy-saving attachment is diffusely used in the transformation of new and old ships due to its easy to fix,reduce spending,and high energy saving effect.Make full use of the space around the propeller,and generally use the attached body to achieve the most ideal effect.This thesis mainly focuses on the research of the ship propeller composite energy-saving attachment technology based on the Boss cap fins and the Pre-duct for the outboard motor propeller used by the small ship.For the fin tilt angle,when the advance coefficient is low,the solution without the fin tilt is a better energy-saving solution,When the advance coefficient is high,the fins inclined to the direction of the propeller rotation direction will have a better energy saving effect.This thesis use CFD means to study and analyze the capability of propellers with cap fins,Analyze the flow field characteristics of the propeller before and after the Boss cap fins is installed and the energy saving mechanism of the Boss cap fins.On this basis,the effect of the characteristic parameters of the Boss cap fins,such as radius ratio,installation angle and fin inclination angle,on the open water efficiency of the propeller was studied.Research indicates: The installation angle of the Boss cap fins is related to the pitch angle at the root of the propeller blade.The best angle is often the same as the pitch angle of the blade root.The radius of the fins is not as large as possible,and needs to be selected according to the propeller.Then carry out research and analysis on the hydrodynamic performance of the propeller with the Pre-duct.The energy-saving mechanism of the Pre-duct is mainly studied,and the influence of the diameter of the Pre-duct and the angle of attack of the duct on the open water efficiency of the propeller after the installation of the duct is studied.The outcome show that the efficiency increases with the increase of the diameter of the duct under the low advance modulus.and at the high advance modulus,The efficiency of the propeller decreases as the diameter of the duct increases.When changing the angle of attack of the duct,within the range of the numerical simulation advance coefficient,When the influence of the duct itself is not considered,the greater the angle of attack of the duct,the greater the open water efficiency of the propeller.When considering the influence of the duct itself,due to the resistance of the duct itself,and the efficiency of the propeller is lower than that when there is no energy-saving attachment.It has a certain energy-saving effect at low flow rates.Finally,the case with the best energy-saving effect of the Boss cap fins and the Pre-duct is combined and installed on the propeller to study the energy-saving effect of the composite energy-saving appendage,and discuss the compound effect of the duct on the Boss cap fins.The results show that the composite energy-saving appendage can more operatively subside the source damage of the wake caused by the rotation of the propeller,and improve the open water efficiency of the propeller.This has engineering guiding significance for the future application of composite energy-saving attachment technology on propellers.