高负荷轴流压气机喘振时叶片动应力

Surge on Blade Dynamic Stress of High Loading Axial Compressor

喘振是压气机中的一种气动失稳形式,破坏性极大。对某高负荷十级轴流压气机喘振过程中叶片的动应力变化开展了试验研究,结果表明喘振时叶片出口脉动静压首先突增,0.1 s后叶片动应变增长至最高值,叶片第二阶动应力已超过疲劳极限,使叶片产生了高周疲劳损伤,出口脉动静压存在与叶片第二阶频率及叶片通过频率相关的后行波/前行波分量,但没有集中出现在某一固定节径下;对叶片开展了颤振数值模拟,结果表明叶片前三阶的积累功小于零,对数衰减率大于零,未发生颤振;通过增加叶片厚度提高叶片频率来提升叶片抗振能力,叶片根部相对最大厚度从0.076增加至0.089,叶片一弯频率对应的共振转速提高了15.2%;试验表明在75%换算转速进喘时,叶片相对应变降低了18%,本文提高叶片频率的方法很好地解决了工程中出现的转子叶片进喘时动应力突增的问题。

Surge is one pattern of aerodynamic instability,and is devastating to compressor.Experimental study on blade dynamic stress of high loading ten-stage axial compressor was conducted.The results show that dynamic static pressure at exit of rotor blade increases quickly when surge happens,followed by dynamic strain to its summit in 0.1 second.Second order of blade dynamic stress exceeds the limitation of fatigue and may produce fatigue damage.Exit dynamic static pressure has relationship both with second order of blade frequency and blade passing frequency in the form of the fraction of forward and backward waves,and the waves are not the fixed nodal.Numerical analysis of flutter shows accumulated work is less than zero and logarithmic damping is more than zero from the first to the third order of blade frequency.Blade thickness is increased,and then blade frequency is added in order to improve anti-vibration ability of blade.The relative maximum thickness(maximum thickness divided by chord)at the root of blade increased from 0.076 to 0.089.The resonance speed of the first order of blade(bending vibration)increases 15.2%.The test shows the relative dynamic strain decreases 18%at the corrected speed of 75%when it surges.The method of improving blade frequency has solved the issue of blade dynamic stress burst increasing when the compressor surges.