A Study on Estimation of Propeller Vibration Characteristics for Development of Low-Noise Propellers

Abstract

Vibration of ship propellers can cause damage to blades and propeller noise, in order to design low-noise propellers the vibration characteristics of propellers must be estimated to a high degree of accuracy and reflected in the design. In this study, in order to estimate the propeller vibration characteristics with high degree of accuracy, a propeller finite element model was created that included the hub and all blades of the propeller and increased the number of finite elements of the blades by about 2.2 times compared to previous studies. The free vibration analysis of the blade finite element model which was a method of previous studies, and the free vibration analysis of the propeller finite element model with fixed or unfixed upper and lower surfaces of the hub were performed. Natural frequencies and mode shapes, which are vibration characteristics of the propeller, were estimated through free vibration analysis, and the effect of the propeller hub on blade vibration was confirmed by analyzing the estimation results. In addition, an impact test was performed, and the accuracy of the estimation of the vibration characteristics was analyzed by comparing the test results with the estimation results of the vibration characteristics. As a result, the propeller have modes with similar natural frequencies and blade mode shapes, this phenomenon occurs because of the coupling effects in which the vibration of a blade affects the vibration of another blade through a hub. The propeller hub affects the blade vibration by the coupling effects and the hub vibration and when the upper and lower surfaces of the hub are fixed, the hub vibration does not affect the blade vibration. In order to estimate the vibration characteristics of the propeller with high degree of accuracy, it was derived that vibration analysis should be performed for the propeller, not just the propeller blade.