Optimal Propeller Design Method Accounting For Hub Effect

With the dual drive of ship energy conservation and discharge decreasing, more attention is paid to the design and application of high efficiency propeller. Optimal propeller design method is an important issue in propeller theoretical design with well-developed theory background and application value. However, accounting for hub effect, existing method treats hub as an infinitely long cylinder with image vortex placed in it. This is not an absolutely accurate model because of some weakness. The optimum propulsion design method accounting for hub effect is discussed and a surface panel method for hub modeling is adopted. This attempt is of academic significance and engineering value.Firstly, an integrated lifting line and surface panel method is proposed for optimum propeller design with hub modeled by surface panel method. To establish the hub induced velocity with the unknown circulation distribution of blades, an integrated influence factor is presented.Secondly, some numerical problems are discussed along the programming procedure especially the singularity occurs at root. The numerical reliability is well analyzed and some suggests on numerical method are suggested for wake meshing and lifting line meshing.Thirdly, applying this integrated method, several DTMB 4119 replicas are designed with different hub models. Detailed analysis shows that this design method is effective on hub effect. Then, analysis of hub geometry and wake effect on optimal circulation is presented. It is suggested that hub radius has significant effect and wake adapted design should be conducted in propeller design.Take the propeller design issue of a bulk carrier as example, difference between the design results from circulation distribution of design packages and that from optimal design is analyzed. The result shows that optimal circulation distribution can achieve the highest efficiency.Finally, the hub induced drag is discussed which should be considered in the theoretical design procedure. Hub induced drag has approximately 1% negative effect which should be wellconsidered in optimal design method.