关键词: 极地螺旋桨, 系柱工况, 空化, 推力下降, 模型试验, 数值模拟

Abstract: The polar ships during ice-breaking operation are often in bollard conditions or low advance speed conditions, easily causing propeller cavitation with a decrease of thrust and a serious impact on the ice-breaking capability. The thrust reduction caused by the cavitation of the ice-class propeller under the bollard condition is studied using both the model test method and the numerical simulation method, in order to guide the hydrodynamic performance design of the ice-class propeller. Firstly, the open-water test and the thrust reduction test under the bollard condition are performed for a self-designed ice-class propeller in the cavitation tunnel. The results show that the model test cannot meet the zero-advance-speed condition, and thus cannot truly reflect the thrust reduction of the propeller under bollard condition due to the space limitation of the working section of the cavitation tunnel and the influence of the induced velocity of the propeller. Therefore, the numerical simulations based on the commercial CFD software Star-CCM+ are further carried out. The numerical accuracy is verified by comparing the results of the open-water simulation with those of the model test, and then the numerical simulations of the thrust reduction are performed under the bollard condition and the low advance speed condition. It shows that the thrust reduction measured by the model test under the bollard condition is consistent with the numerical results under the low-advance-speed condition. As for the simulation under the bollard condition, it is observed that the start point of the thrust reduction of the propeller appears earlier than that under the low-advance-speed condition. The thrust of the ice-class propeller begins to decline rapidly when the cavitation number equals to two (σ_n=2), and decreases to 43.9% of the thrust under open-water condition with a cavitation number of σ_n=1, resulting in a significant deterioration of hydrodynamic performance. By analyzing the mechanism of the thrust reduction under the bollard condition, it is found that the thrust reduction is mainly caused by the significant decrease in average pressure on the blade surface under the influence of the cavitation occurring on the back of the blade.

Key words: ice-class propeller, bollard condition, cavitation, thrust reduction, model test, numerical simulation