脉动内流作用下L型弯管应力&振动特性实验研究

Experimental study on stress and vibration characteristics of L-type elbow under pulsating flow condition

为探究脉动内流对输流弯管流固耦合的影响,对不输送压力的脉动内流作用下,"L型"弯管的应力&振动特性进行了实验研究。实验结果表明:开泵阶段弯管弯折段上端面和外侧面的ε_(max)值(应变最大值)、a_(pp)值(径向振动加速度峰峰值)、S_(pp)值(径向振动位移峰峰值)均比平稳阶段的大,说明开泵时的"水锤效应"对弯管的影响程度大且不容忽视;开泵阶段和平稳阶段弯管弯折段上端面所受应力的波动幅度、a_(pp)值、S_(pp)值均比外侧面的大,说明上端面更容易出现应力疲劳破坏,且上端面径向振动更易造成管道系统的失稳;平稳阶段,随着P_(max)(最大输送压力)的增大,弯管弯折段上端面和外侧面的ε_(max)值增大,但增幅降低,a_(pp)值减小,S_(pp)值减小且减幅增大,说明随着P_(max)的增大,管道输流愈平稳,脉动内流与弯管的耦合振动强度逐渐减小。

In order to explore the impact of fluid-structure coupling on the elbow conveying pulsating flow, an experimental study on stress and vibration characteristics of 'L-type' elbow under pulsating flow in different delivery pressure conditions is made. The experimental results showed that the ε_(max)(the maximum strain), a_(pp)(the peak to peak values of radial vibration acceleration) and S_(pp)(the peak to peak values of radial vibration displacement), which are on the upper end and the outer side of the elbow bent segment, are bigger than those of the stationary phase during the phase of opening the pump. It is indicated that the influence of 'water hammer effect' to the elbow is great and can't be ignored. The strain fluctuations, a_(pp) and S_(pp), which are on the upper end of the elbow bent segment, are bigger than those of the outer side during the phase of opening the pump and the stationary phase. It is indicated that the upper end is more prone to occur tensile fatigue damage and its radial intensity is more prone to cause the instability of the piping system. During the stationary phase, on the upper end and the outer side, with the P_(max)(the maximum delivery pressure) is increased, the ε_(max) increase but their amplitudes decrease, the a_(pp) decrease, the S_(pp) decrease and their damping increases, which indicates that with the increasing of the P_(max), the pipeline conveys more smooth, and the coupling intensity between the pulsating flow and the elbow gradually decreases.