叶轮行波振动下的气动阻尼计算 *

Calculationof Aerodynamic Dampingforan Impeller under Travelling Wave Vibrations

关键词:  离心叶轮  网格变形  气动阻尼  行波振动  紧支径向基函数  二叉树

Key words:  Centrifugal impeller  Grid deformation  Aerodynamic damping  Travelling wave vibration  Compactly supported radial basis function  Alternating digital tree

摘要:

为展开运动边界下离心叶轮流场的数值分析，独立开发了网格变形程序和非定常流动模拟程序，实现了流场中振动离心叶轮的气动阻尼计算。采用紧支径向基函数法进行结构到气动表面变形的数据传递，应用二叉树技术进行壁面距离的计算，大幅提高了网格变形和流场分析中距离搜索的计算效率。通过振动叶栅和径向叶轮的算例，验证了程序应用于运动边界流场计算和叶轮流场模拟的正确性。以半开式叶轮为对象，展开其在行波振动条件下气动阻尼的计算分析。结果表明，叶轮在前、后行波振动下的气动阻尼均为正，后行波振动引起的气动推力和气动阻尼较大，叶轮表面的平均气动功率密度呈现循环对称的分布特征。

Abstract:

In order to carry out the numerical analyses of the flow fields with moving boundaries in centrifu. gal impellers，the codes for the grid deformation and the unsteady flow simulations were developed independent. ly，by which the calculations of the aerodynamic damping of centrifugal impellers were realized. By adopting the compactly supported radial basis function to carry out the data transfer of surface deformation from the structure mesh to the flow mesh，and utilizing the alternating digital tree technique to fulfill the wall distance calculations， the computation efficiencies of grid deformation and flow-field analyses were greatly increased. By the test casesof an oscillating cascade and a radial impeller，the correctness of the code for the simulations of the flow-fields with moving boundaries and the flows in centrifugal impellers was validated. Then taking a semi-open impeller as the research object，the calculations of aerodynamic damping under travelling wave vibrations were carried out.The results show that，the aerodynamic dampings of the impeller are both positive under the forward and back.ward travelling wave vibrations.The aerodynamic thrust and the aerodynamic damping induced by the backward travelling wave vibration are larger. The average aerodynamic power density on the impeller surface exhibits a cy.clic symmetric distribution.