Analysis Of The Influence Of The Chordwise Loading Distributions On Propeller Efficiency And Cavity And Improvement Of Design Program

The international competition of ship propeller design is becoming increasingly fierce,more attention is paid to the competition of efficiency and cavity performance.It's helpful to improve efficiency of propeller by using optimal propeller design method,however,there is little research on whether the chordwise loading distributions have effects on efficiency.Generally,for purpose of improving the efficiency,the area ratio was decreased,therefor,cavity was aggravated,causing the risk of erosion.Herein,different types of chordwise loading distributions are used to design the propeller.And analysis of the influence of chordwise loading distribution on efficiency and cavity of propeller are made.Additionally,the lifting-surface design program which CSSRC used currently is based on a simplified boundary condition,which in two-dimensional form,there is room of improvement.Herein,three-dimensional boundary condition is used,as the method of calculating the propeller geometry,the new lifting surface design program is established.Firstly,the boundary condition of propeller was analyzed.The lifting surface design program which use three-dimensional boundary conditions is established,and program is verified by the old program.It is suggested that the differences of propeller geometry and hydrodynamic performance are small by two programs in the case of small rake.But three-dimensional boundary conditions should be used to design propeller with large rake.Secondly,the hydrodynamic predictions of propeller which have high efficiency are made by panel method program.Analyzing the chordwise loading distributions of these propeller to establish new models of chordwise loading distributions.Thirdly,lifting-surface method designs are made by using different chordwise loading distributions of a container ship.Hydrodynamic validations of each propeller are made by CFD method.Pressure predictions are made by steady panel method,and the final strategies are chosen.Unsteady panel method are used to predict the pressure of final strategies.Finally,the models of final strategies are manufactured.Hydrodynamic and cavitation observation and pressure fluctuation measurement tests for these model propellers of the container ship are performed in the large cavitation channel of CSSRC.The results show that chordwise loading distributions have no obvious effects on efficiency,but have more significant influences on cavity.It is suggested that new chordwise loading distributions could be used at outer radius at the design stage to increase the strength of cavity,and let cavity break out of blade area.Thus,erosion risk may be reduced.