The influence of the number of blades of the blade propeller on its vibro-active and propulsive qualities at operation in the uneven velocity field behind the vessel hull is considered in the paper. The analysis begins with the theoretical considerations, which give a reason to believe that increasing the blades number should lead to decreasing the value of hydrodynamic forces affecting the propeller vibro-activity. This analysis takes into account the known property of any blade propeller, which consists in the fact that at operation in the uneven velocity field, not all of its harmonics are manifested on it in a power relation. This property is called filtration, when the blade propeller reacts to the emphasis from the harmonics of the field, multiples of the number of blades. Since the harmonics as the members of the Fourier series are decreasing in magnitude, then the magnitude of the variable forces on the blade propeller should decrease with increasing the number of its blades. To confirm the obtained theoretical result, the experimental data obtained under the laboratory conditions are used. They are based on the results of the acoustic measurements obtained in the cavitational pipe. At the same time, it is assumed that the contribution of the blade propeller is made mainly by the power acoustic radiation of the functioning propeller in the uneven velocity field at frequencies multiple to the blades number per frequency of its rotation. Thus, when obtaining the experimental data, not directly variable forces on the blade propeller are measured, but only its force acoustic radiation is recorded. The study is based on the fundamental principle: there are variable forces -there is an acoustic field, there are no variable forces -there is no acoustic field. The experimental data have shown that an increase in the blades number on the blade propeller favorably affects reducing the propeller vibration characteristics. Along with this, it is also noted that with a decrease in the propeller vibration characteristics, a decrease in the propulsive quality of the propeller is observed.
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