基于流固耦合的错位桨搅拌假塑性流体模态分析

MODAL ANALYSIS OF IMPELLER OF PERTURBED SIX-BENT-BLADED TURBINE BASED ON FLUID-STRUCTURE INTERACTION

模态分析是指运动构件在正常工作时为避免发生共振现象而运用的一种分析方法。文章采用基于双向流固耦合的运算方法,对错位六弯叶桨(6PBT)在静模态和预应力模态下的固有频率和振型图进行对比分析。预应力模态分析在流变指数分别为n=0.9、0.7和0.5的黄原胶溶液(一种比较典型的假塑性流体)中进行。结果表明:流体流变性对桨叶的振型分布和模态频率基本没有影响,在静模态和预应力模态下6PBT桨的振型分布相同,均表现为1~6阶为扭转振型,7~10阶为弯曲振型,桨叶的模态频率并未发生较大变化,说明搅拌介质与桨叶的相互耦合作用并没有对6PBT桨的模态造成很大影响。因此6PBT桨在搅拌不同流变指数的假塑性流体时,其固有频率和振型分布具有稳定性的特点,在很大程度上降低了搅拌桨在搅拌过程中出现共振现象的概率。

Modal analysis is an analytical method used to avoid resonance in the working state of moving link.The natural frequency and vibration shapes of the 6 PBT impeller in static mode and prestressed mode are analyzed by using bidirectional fluid-structure interaction calculation method.The working medium of the prestress modal analysis is carried out in a xanthan gum solution(a typical pseudoplastic fluid)having a rheological index of n=0.9,n=0.7,n=0.5 respectively.The results show that the fluid rheology property of the pseudoplastic fluid has little effect on vibration shapes and modal frequency of the blade.The distribution of the vibration shapes of the 6 PBT impeller are basically the same in static mode and prestressed mode.Between the steps of 1 st and 6 th,the blade mode appears torsional;between the steps of7 th to 10 th,the blade modal shape appears bending.The modal frequency of the blade does not change much,indicating that the coupling effect between the stirring medium and the blade does not affect the mode of the 6 PBT paddle much.Therefore,the natural frequency and vibration shapes distribution of the6 PBT impeller is stable under the pseudoplastic fluid of different rheological index,which reduces the probability of the resonance phenomenon during the agitation process greatly.