Numerical And Experimental Study On Open Water Characteristics Of Ducted Controllable-pitch Propellers

As a special propeller, ducted controllable pitch propeller has both the advantages of ducted propeller and controllable pitch propeller, which can reduce consumption and extend the voyage time. It can be applied to fishing boats with complex operation conditions. The influence of duct to the hydrodynamic performance of ducted controllable pitch propeller is important. Different parameters of the duct, pitch ratio and the match with propeller will affect the open water performance of ducted controllable pitch propeller.At first, this paper chooses the combination of 19A+Ka4-70 as a duct propeller. By using different number of the grid, the grid independence is verified before compared with experiment result. Then the forecast effects of chosen parameters such as turbulence model and boundary condition are sure. On this basis, analyze the change of open water performance by different combination of duct and propeller, including the length of the duct, the shape of duct front edge and the gap between duct and propeller and clearance distribution. Through calculation and analysis, it is found that, to a certain duct section, reduce the tail length and the thickness on the front of the change will affect the hydrodynamic performance of ducted propeller. The effect of tail length of improved to better. In addition,there is also a critical value between duct and propeller clearance changes. The hydrodynamic performance change rules with clearance of duct propellers are different in cases above the critical values and below the critical values. The distribution of the upper and lower clearances between the duct and the propeller has little effect on the hydrodynamic performance, but the damage caused by the long-term work will be affected. Through these conclusions, we can provide reference for the design or adjustment of the duct.Then in this paper, a designed high skewed controllable pitch propeller is calculated by CFD. The open water performance curves under different pitch ratios were calculated. After introducing the open water performance experiment, compare the calculation results and experiment results. The range of error in engineering is allowable and then the reasons are analyzed. On this basis, by changing the model of boundary layer grid layout, we analyze the influence of boundary layer grid on the numerical calculation, and obtain the good results of the boundary layer grid layout. Then we analyze the influence of the pitch ratio of the ducted controllable-pitch propeller, and a best pitch ratio exits in different conditions. Finally, by changing the gap between the duct and the highly skewed propeller, it is obtained that the gap law also applicable to the propeller with different blade shapes.