Methods Of Vibration Reduction Of Propeller

(1) Increase the installation clearance between propeller and hull
According to the data, the clearance should be more than 0.12D~0.2D. The larger the propeller diameter is, the larger the clearance is, which can reduce the surface excitation force transmitted to the hull. Considering the actual situation of the ship, if the clearance cannot be increased, the hull damping cavity can be set, that is, a "notch" can be recessed above the hull corresponding to the propeller. The size of the "notch" and the recessed size correspond to the size of the propeller diameter, which is equivalent to using the spring effect of water quality points, To reduce the surface excitation force transmitted to the hull.
(2) Set damping material
Steel or rubber damping materials shall be laid in a large enough range above the propeller in the hull. When laying, attention shall be paid to the cleaning of the steel structure surface to ensure the bonding effect of damping materials and steel structure. The damping materials shall be used to generate tensile, bending, shear and other deformations in its interior, absorb a large amount of incident energy, and consume the vibration energy into heat energy.
(3) Increase the number of blades
In general, increasing the number of blades can improve the balance of the propeller, thus reducing the surface force produced by the propeller on the main hull.
(4) Improve the line shape of the ship's stern
It can improve the wake distribution and the uniformity of the wake field. Of course, considering the complexity of the wake field, we need to combine ship model test to better achieve this. Qualitatively, the adoption of double tail type and the addition of tail fins can improve the tail wake well.
(5) Avoid cavitation
The root cause of cavitation is that the water velocity on the blade section is too fast, the pressure drop is obvious, and the pressure on the unit area of the propeller is too large. In addition to the erosion of the propeller, cavitation will also induce the excitation of the propeller. To improve the cavitation of the propeller, we can reduce the propeller speed by increasing the disc ratio of the propeller.
(6) Installing guide tube
For propellers with large loads, ducted propellers can be used. On the one hand, the draft tube can improve the efficiency of the propeller, on the other hand, it can improve the distribution of the wake, and at the same time, it can bear a considerable part of the load originally acting on the propeller, so as to avoid cavitation and vibration of the propeller.