Effect of Manufacturing Tolerances on Performance of Marine Propellers

螺旋桨空泡是船舶的主要问题，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用计算机数控（CNC）粗加工的铸件手工完成的。螺旋桨表面的手工磨削会导致不准确性和设计偏差，这可能导致螺旋桨在效率、气穴和噪声方面的性能下降。船舶螺旋桨的制造通常符合ISO 484标准，该标准规定了制造公差。作为加拿大的主要螺旋桨制造商，Dominis Engineering需要证明，通过CNC加工技术实现的高精度水动力表面可以提高螺旋桨的性能。将使用计算流体动力学（CFD）模拟对螺旋桨制造公差进行调查。该研究将集中在全尺寸改进的NACA 66截面的2-DCFD模拟上，考虑到由于制造公差而引起的几何形状（弦长，弯度和厚度）的变化。该项目的结果将使Dominis能够开发改进的螺旋桨制造工艺，提高生产效率和高精度，以减少噪音和振动，并提高燃油效率。它还将使Dominis能够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，这将最终使加拿大经济受益。

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.