Influence Of The Steam Flow Exciting-vibration On Stability Of Shafts In Ultra-supercritical Unit

In recent years,due to the structural adjustment of power industry in China,the ultra-supercritical unit with high efficiency has rapidly developed to be an important part in power generation system.But high parameters of the unit come with increasing instability of rotor shafting caused by steam flow exciting-vibration,restricting its development.This paper aims to investigate the influence of steam flow exciting-vibration on the stability of rotor shafting,which would hopefully help to improve the design,manufacture,operation,maintenance and fault diagnosis of the unit.In this paper,the influence of steam flow force produced by bypass compensating steam and balanced shaft seal on rotor stability was calculated and analyzed by Riccati transfer matrix method.Firstly,within the radial intake model and tangential-axial model,the velocity field and temperature field in the compensating steam chamber and its next stage stator blade were calculated under conditions of different total amounts of compensating steam and different differences between upper and lower compensating steam flow.Meanwhile,the influence of compensating steam on aerodynamic performance of flow passage was analyzed,as well as the steam flow force on the rotor surface calculated.Secondly,a calculation program was compiled based on transfer matrix method,and the discrete model and the bearing dynamic characteristics of the rotor shafting were established and calculated.Then,the stiffness,converted from steam flow force with aforementioned conditions and the balance shaft seal,was superimposed on the stiffness of bearing oil film to analyze the effect on the rotor stability.The result shows that the effect of the balance shaft seal on stability of the rotor system is much greater.Finally,the influence of several factors,such as the length of the shaft seal,the radius clearances,inserting chamber into seals and the bearing width,on stability of the rotor was calculated and analyzed.Then a modified plan was proposed,which could increase the stability of the shafting system from 0.0632 to 0.3148.