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

摘要： 极地船舶破冰航行时,常处于系柱工况或低进速工况,此时易发生螺旋桨空化,引起推力下降,严重影响破冰能力。为有效指导极地螺旋桨水动力性能设计,该文从模型试验和数值模拟这2种方法入手,针对极地螺旋桨系柱工况下由空化引起的推力下降问题进行研究。首先,在空泡水筒设施中分别开展某自主设计极地螺旋桨的敞水性能试验和系柱工况推力下降试验。结果表明：受空泡水筒工作段空间限制与螺旋桨诱导速度影响,模型试验难以满足零进速条件,无法真实反映系柱工况的螺旋桨推力下降特征。为此,文中进一步开展基于Star-CCM+软件的数值模拟研究。通过对比敞水预报结果与模型试验结果,验证了数值计算精度,并开展系柱工况和低进速工况的推力下降数值模拟。结果表明：模型试验测得的系柱工况推力下降趋势与低进速工况数值结果相符,而在系柱工况模拟中,螺旋桨推力下降点与低进速工况相比出现更早,转速空化数σ_n=2.00时,推力即开始迅速下降;转速空化数σ_n=1.00时,该极地螺旋桨推力下降至敞水工况的43.9%,造成水动力性能显著恶化。分析系柱推力下降机理机制,发现其发生的主要原因是叶面平均压力在叶背空泡影响下大幅减小。

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