Mistuning with Aero-coupling II (Mistuning of Aerodynamically and Structurally Coupled Bladings)

“气动耦合混调II”项目旨在为叶轮机械失谐叶片盘振动的数值预报提供一种实验验证的模拟方法。通过对不同叶盘组件振动的实验测量，验证了前一个项目中建立的降阶模型。开发的程序ROMI(失谐涡轮叶片的降阶模型)允许在考虑气动和通过护罩和平台下阻尼器的非线性耦合的情况下进行高效的数值振动模拟。以气动耦合压气机叶盘和叶根非线性耦合(燕尾联接)的压气机转子在真空中旋转为实验样机。利用叶尖定时系统测量了叶盘在流体流和扬声器激励下的受迫振动。用磁激励和应变计对叶片-圆盘节点的非线性进行了实验研究。通过将降阶模型与特定于所安装的试验台及其运行条件(叶片根部耦合、离心力、流体压力和温度)的边界条件进行补充，以确保数值结果和实验结果的可比性。为了能够有效地对几何复杂的冷杉树根进行建模，简化方法被扩展了一个额外的步骤，以减少与接触界面相关的自由度数。此外，还研究了不同振型下气动耦合系数与振动频率的关系。基于本研究的结果，发展了一种气动替代模型，可有效地逼近随频率变化的气动耦合系数。

The project "Mistuning with aerodynamic coupling II" aims at providing an experimentally verified simulation method for the numerical prediction of mistuned bladed disk vibrations in turbomachinery. The reduced order model (ROM), developed in a previous project, is validated by experimental vibration measurements of various bladeddisk assemblies. The developed program ROMI (Reduced Order Models for Mistuned Turbine Blades) allows numerically efficient vibration simulations under consideration of aerodynamic and nonlinear couplings by shrouds and underplatform dampers. Anaerodynamically coupled compressor blisk and a compressor rotor with nonlinear blade root coupling (dovetail joint) rotating in vacuum are used as experimental demonstrators. The forced vibrations of the blisk, excited by the fluid flow and acoustic speaker excitation, are measured by means of a tip timing system. The experimental invacuostudy of nonlinear blade-disk joints is performed with magnetic excitation and strain gauges. The comparability of numerical and experimental results is ensured by complementing the reduced order model with boundary conditions which are specific to the installed test rigs and their operation conditions (blade root coupling, centrifugalloads, fluid pressure and temperature) and which so far have not been considered in the model. To enable the efficient modelling of geometrically complex fir-tree roots, the reduction method is extended by an additional step to reduce the number of degrees of freedom related to contact interfaces. In addition, the dependence of aerodynamic coupling coefficients on the vibration frequency is studied for different mode shapes. Based on the outcome of this study, an aerodynamic surrogate model is developed for thenumerically efficient approximation of frequency-dependent aerodynamic coupling coefficients.