Experimental investigation of vibrating compressor blades in the presence of a periodic unsteady inlet flow

该项目将有助于压缩机叶片对低频小振幅激励响应的物理理解。这些激励会导致压气机叶片的疲劳损伤，但通常没有充分建模，导致这种现象的原因不容易预测。柏林工业大学航空发动机系配备了一个用于气动弹性研究的工作风洞。实验装置的测量部分由一个大型的11叶片压气机叶栅组成。其中九个叶片可以通过步进电机被迫在俯仰和俯冲中振动。该设施的模块化设计旨在集成一个产生非定常周期性入口流的系统。该机构旨在安装在压气机叶栅的上游，并允许实现不同的激励模式。将测量和比较不存在和存在周期性非定常进口流时的非定常气动叶片响应。因此，周期性进口流对叶片气动响应的影响将被量化。本项目的评估将侧重于低频和小振幅激励。将通过改变激励参数和评估叶片运动和入口激励之间的相位来检查线性理论描述所研究问题的适用性。计划的研究将采用最先进的技术进行。将进行热线测量，以表征周期性入口流量。叶片表面的非定常压力分布将通过压阻式压力传感器获得，而振动频率和振幅将通过应变片测量来反演。

This project will contribute to the physical understanding of compressor blade response to low-frequency, small-amplitude excitations. These excitations -- which can lead to fatigue damages of compressor blades -- are often inadequately modeled, being the causes of such phenomena not easily predictable.The Chair of Aeroengines at the Technische Universität Berlin is equipped with an operating wind tunnel for aeroelastic investigations. The measurement section of the experimental facility consists of a large-scale compressor cascade with eleven blades. Nine of the blades can be forced to vibrate in pitch and plunge by means of stepper motors. The modular design of the facility is conceived to integrate a system for generating unsteady periodic inlet flows. This mechanism is meant to be installed upstream the compressor cascade and allows to realize different excitation patterns. The unsteady aerodynamic blade responses in the absence and presence of a periodically unsteady inlet flow will be measured and compared. As a result the effects of periodic inlet flows on the blade aerodynamic response will be quantified. The assessments of this project will be focused on low-frequency and small-amplitude excitations. The suitability of the linear theory to describe the investigated problem will be checked by varying the excitation parameters and by evaluating the phase between the blade motion and the inlet excitation.The planned investigations will be performed with state of the art technology. Hot wire measurements will be carried out to characterize the periodic inlet flow. The unsteady pressure distribution on the blade surface will be acquired by means of piezoresistive pressure transducers, whereas the vibration frequency and amplitude will be retrieved with strain gauges measures.