Effect of Manufacturing Tolerances on Performance of Marine Propellers

螺旋桨空化是船舶主要关注的问题，因为它是螺旋桨产生的噪声和振动的主要来源。在了解螺旋桨制造公差对螺旋桨性能的影响方面所做的努力非常有限。今天制造的大多数螺旋桨都是手工完成的铸件，使用计算机数控（CNC）进行粗略加工。手工研磨螺旋桨表面会导致不精确和偏离设计，这可能导致螺旋桨在效率、空化和噪音方面的性能下降。船舶螺旋桨通常是按照ISO 484标准制造的，该标准规定了制造公差。作为加拿大的主要螺旋桨制造商，多米尼克工程公司需要证明，通过CNC加工最终成型和精加工技术可以实现的高流体动力表面精度，提高了螺旋桨的性能。螺旋桨制造公差的研究将采用计算流体动力学（CFD）模拟。考虑到制造公差导致的几何形状（弦长、弧度和厚度）的变化，拟议的研究将集中在全尺寸修正NACA 66截面的2-DCFD模拟上。该项目的成果将使Dominis能够在生产效率和高精度方面开发改进的螺旋桨制造工艺，以降低噪音和振动，并提高燃油效率。它还将使多米尼克进一步支持加拿大造船战略和加拿大在船用螺旋桨制造方面的全球竞争力，这最终将使加拿大经济受益。

Propeller cavitation is of major concern for ships since it is the predominant source of propeller-generatednoise and vibration. Very limited efforts have been made to understand the impact of propeller manufacturingtolerances on the propeller performance. The majority of propellers manufactured today are hand-finished fromcastings which are roughly machined using Computer Numerical Control (CNC). Manual grinding of propellersurfaces introduces inaccuracies and deviations from design, which could lead to degradation of propellerperformance in terms of efficiency, cavitation and noise. Ship screw propellers are typically manufactured tomeet the ISO 484 Standard, which specifies the manufacturing tolerances.As the key propeller manufacturer in Canada, Dominis Engineering needs the evidence that the high precisionof hydrodynamic surfaces, which can be achieved by the technology of CNC machining to final form andfinish, improves propeller performance. The investigation into propeller manufacturing tolerances will becarried out using computational fluid dynamics (CFD) simulations. The proposed research will focus on 2-DCFD simulations of a full-scale modified NACA 66 section, considering the variations in geometry (chordlength, camber and thickness) due to manufacturing tolerances.The outcomes of the project will enable Dominis to develop improved processes of propeller manufacturing interms of efficiency of production and high precision for reduced noises and vibrations as well as increased fuelefficiency. It will also enable Dominis to further support the Canadian Shipbuilding Strategy and Canada'sglobal competiveness in marine propeller manufacturing, which will ultimately benefit the Canadian economy.