压气机线性振荡叶栅气弹试验研究(二)：叶尖间隙的影响

Experimental Study on Aeroelasticity in Linear Oscillating Compressor Cascade.PartⅡ:Tip-clearance Effect

为了加强对叶轮机三维气动弹性机理的理解,为数值模拟方法提供试验验证数据,开展了压气机线性叶栅气动弹性试验研究。本研究分为2个部分,第1部分研究压气机线性振荡叶栅的气弹稳定性,本文为第2部分,重点辨别叶尖间隙对压气机叶片气弹稳定性的影响。试验结果表明随着叶尖间隙的增加,间隙流对振动叶片有失稳影响,其影响范围几乎遍及整个叶高,这与非定常气动的瞬时径向相互作用的结论是一致的。这种失稳效应与叶片间相位角对叶栅气弹稳定性的影响不耦合。间隙流在叶栅稳定性最差时影响最显著。详细的非定常压力试验结果表明,随着叶尖间隙的增加,叶片表面非定常压力幅值减小区域与间隙流造成的卸载区域相对应。由试验结果可以推断,不考虑叶尖间隙的数值模型可能会给出过稳定的叶片颤振预测。

An experiment is carried out to enhance the understanding of three-dimensional（3D） blade aeroelastic mechanisms and to produce the experimental data for the validation of numerical methods.This is PartⅡof a two-part series.Part Ⅰ describes the experimental study on the aeroelastic stability of the compress oscillating cascade.The emphasis of this part is to identify the tip-clearance effects on the aeroelastic response of the same oscillating cascade.The blades are aeroelastically destabilised as the tip gap is increased,and the destabilised region is seen to extend to almost the whole blade span,which is consistent with the strong spanwise unsteady interaction.This destabilising effect of tip-clearance is independent on inter-blade phase angle with the maximum effect at the least stable inter-blade phase angle.The chordwise trend in amplitude of unsteady pressure with increasing tip clearance is observed in the regions where the tip leakage flow has an obvious effect on the corresponding steady loading.The results clearly demonstrate that numerical methods without tip-clearance effect might over predict cascade stability.