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Outline
During the operation of the ship propulsion shafting system, it is often excited by the friction of the water-lubricated stern bearing, which in turn induces self-excited vibration noise. The results of sea trials show that this type of vibration exhibits the characteristics of a certain order of the natural frequency of torsional vibration of the propulsion shafting system and its harmonic frequency components in the vibration spectrum. In order to explore the causes of such vibrations and propose an effective criterion formula, this study employs the finite element method to construct a nonlinear torsional vibration analysis model of the propulsion shafting system under the friction excitation of the stern bearing. The shooting method is applied to explore the influence of key parameters, such as the rotational speed of the shafting system, the structural damping ratio, the inclination degree of the shafting system, and the propeller excitation, on this vibration. The study finds that the root cause of this type of vibration lies in the existence of local torsional vibration modes near the stern bearing. The lower the rotational speed and the greater the friction force, the more likely this type of vibration is to occur. The inclination of the shafting system will increase the local friction force, thereby increasing the probability of this type of vibration. The blade frequency excitation force of the propeller will cause a sideband phenomenon in the spectrum of the self-excited vibration, that is, a series of equally spaced blade frequency components will form on both sides of the self-excited vibration frequency. Through in-depth analysis of a large amount of data, this study proposes a criterion formula to determine whether the propulsion shafting system will undergo frictional torsional self-excited vibration, and verifies the effectiveness through numerical calculations. This criterion formula can provide an important theoretical basis for the design of early fault warning mechanisms of the ship propulsion shafting system.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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