多级压气机转子负荷系数对叶片非同步振动的影响

Effect of aerodynamic loading coefficient on occurrence of nonsynchronous vibration in a multi-stage compressor

通过理论计算分析与试验研究,解释了核心机试验中调节叶片(VSV)异常偏关引起的转子叶片非同步振动(NSV)现象。首先对出现叶片振动的前1.5级压气机进行了全环非定常数值模拟研究。数值结果表明当第1级静叶安装角从偏关2°逐渐调节到偏关6°时,第1级转子叶片负荷逐渐增加,并出现明显的分离流动结构,该流动现象在转子叶片上产生非整数倍转频的压力脉动激励,这是典型的旋转失稳(RI)现象特征。为进一步研究旋转失稳诱发非同步振动与转子气动负荷之间的关联,在6级跨声压气机试验件上开展了系统性的计算与试验研究。通过二维通流计算评估了不同进口导叶/静叶(VIGV/VSV)角度下,第1级转子负荷随转速的变化规律。进而通过6级压气机试验,观察到当第1级静子叶片调整到偏关8°以及第1、第2静子叶片同时调整到偏关4°和偏关3.6°时,第1级转子叶片均出现了非同步振动现象。通过分析第1级转子叶片表面应变的频谱和机匣动态压力脉动的频谱,建立了二者的内在关联。明确了除叶尖径向间隙大外,可调导叶/静叶偏关同样会在转子叶尖形成高负荷,导致叶尖区域流动不稳定进而诱发叶尖旋转失稳现象。研究结果对于多级压气机的设计工作具有重要的指导意义。

Through theoretical computation,analysis and experimental research,this paper elucidates the Non-Synchronous Vibration(NsV)phenomenon of rotor blades caused by the Variable Stator Vanes(VSV)which are un-expectedly closed from design point in a core engine test.To reveal the underlying mechanism,three-dimensional full-annulus unsteady numerical simulation is initially performed on the first 1.5-stage compressor where blade vibration is observed.The numerical results show evident flow separation at the rotor blade tip as the installation angle of the first-stage stator blade is closed from 2°to 6°,along with the progressively increase of stage loading of the first-stage rotor.Pressure fluctuation peaks are generated at non-integer multiples of rotational frequency by the unsteady vortex shed-ding,which is recognized as the characteristic of Rotating Instability(Rl).Further,the dependence of the occurrence of Nsv induced by Rl on the stage loading is systematically calculated and experimentally investigated on a 6-stage transonic compressor.Two-dimensional through-flow simulations are performed to estimate the change in the stage loading of the first-stage rotor with rotational speed under different Variable Inlet Guide VanesNariable Stator Vanes(ViGVNSV)angles.Through a 6-stage compressor test,the analysis on the spectra of strain and pressure fluctua-tions indicates that NsV is excited on the first-stage rotor by RIl when the first-stage stator is adjusted to-8°,which in-creases the stage loading of the first-stage rotor.The Nsv is also observed when the first-stage stator and the second-stage stator are adjusted to-4°and-3.6°,simultaneously.The present results clarify that besides large radial tip clearance,the closing angle of VIGVNSV can also form high loads at the rotor blade tip,leading to flow instability in the blade tip region and then inducing Rl.The findings of this research are of significant guidance to the design of a multistage compressor.