U形管内气液两相流诱导振动特性的试验研究

Experimental study on the gas-liquid two-phase flow-induced vibration in a U-tube

试验研究了横向U形管内气液两相流诱导振动的动态响应特性。重点研究了流型形式、气相表观流速U_(g)、液相表观流速U_(l)、体积含气率β等对振动响应强度a_(rms)的影响。结果表明,横向U形管振动主要表现为面内方向且为某一阶固有频率附近的低频振动,同时表现为拍振现象。U形弯头轴向不同测点振动频谱幅值呈现近似抛物线变化,在弯头90°处达到最大。a_(rms)由大到小依次为段塞-波形流、环状-波形流、环状-弥散流、塞状-泡状流和分层-塞状流。当U_(l)固定时,a_(rms)随U_(g)的增加呈现先缓慢增长而后快速增大的趋势,快速增大的分界线约为U_(g)=1 m/s;当U_(g)固定时,a_(rms)随U_(l)的增加逐渐增大。当β较小时,a_(rms)随β的增加呈现非常缓慢的增长趋势;当β增加到某节点时,振动强度快速增大,且快速增大的β节点值随液相表观流速U_(l)的增加而降低。

The dynamic response characteristics of the gas-liquid two-phase flow-induced vibration in a transverse U-shaped tube were studied experimentally.The effects of the flow pattern,superficial gas velocity U_(g),superficial gas velocity U_(l),volume void fractionβon the vibration response a_(rms)were studied.The results show that the vibration response in the transverse U-tube mainly presents a flapping phenomenon in plane direction at low frequency nearby a certain order of eigen frequency.The amplitude of the frequency spectrum presents an approximate parabola distribution along the axial measured points of the U-shaped elbow and reaches the maximum at the 90°position of the elbow.The order of the a_(rms)exciter,from high to low,is slug-wavy flow,annular-wavy flow,annular dispersed flow,plug-bubble flow and plug-stratified flow.For a given U_(l),the a_(rms)presents a trend of approximately flat growth and then a sharp increase with the increase of U_(g).The boundary of the sharp increase is about U_(g)=1 m/s.For a given U_(g),the a_(rms)increases with the rise of U_(l).Whenβis small,a_(rms)presents a very slow growth trend with the increasing ofβ.However,whenβincreases to a certain value,a_(rms)increases greatly with the rise ofβ.Furthmore,the value of the greatly increasingβdecreases with the increasing of superficial liquid velocity U_(l).