螺旋桨激励条件下结构振动特性研究

Research on the Propellers Characteristics of Structure Vibration in the Excited Condition

为研究复合材料螺旋桨以及铜质材料螺旋桨在锤击激励以及非稳态激励条件下的结构模态固有特性和水下振动噪声特性,在设计的试验环境下,对处于水介质以及空气介质中的复合材料螺旋桨以及铜质材料螺旋桨5桨叶进行模态激励试验,得到两型螺旋桨各桨叶的固有频率、模态振型以及阻尼比,并分析两型桨5桨叶之间的差异;针对桨-轴系统在临界转速工况下出现空化而导致的异常振动噪声现象,选取螺旋桨发生空化前的辐射水声频谱,对两者进行了对比研究;另外,试验还模拟桨-轴系统在高速运转下的停车运行工况,对停车运行过程的振动噪声时频特性进行分析。试验研究结果表明:前3阶模态中,复合材料螺旋桨各桨叶之间的差异比铜质材料螺旋桨之间的差异要大,但两型桨叶的振型基本一致;螺旋桨发生空化时,产生的叶频及其倍频幅值放大了约2~10倍;停车运行过程中,变流速,变转速产生的变激励力是引起振动噪声时频变幅特性的主因。该研究成果对新材料、新工艺在船舶推进器声学设计有较好的指导作用,对螺旋桨在非稳态激励下的噪声源声学特性有全面认识。

In order to get the characteristics of structure vibration of composite propeller and coppery propeller in the hammer excited condition and unsteady speed excited condition,modal testing is carried out on the composite propeller and coppery propeller in the pool. The modal parameter of natural frequency, damping ratio, and modal shape have been obtained, and the difference between composite propeller and coppery propeller have been contrasted. The spectrum of underwater acoustic radiation between propeller cavitation and propeller re-cavitation have been contrasted. The timefrequency characteristics of the propellers have been analysis during the inertial slowing down period from a high rotating speed. The results of test show that the differences of modal parameter in composite propeller are more than the differences of modal parameter in coppery propeller, but the vibration modal of two kinds of propeller are identical. The amplitude of blade frequency and harmonic frequency has been amplified 2-10 times. In addition, the variant time-frequency characteristics of structure vibration was excited by the variable force due to the variable flow and speed, during the inertial slowing down period from a high rotating speed.