Research On Steam-indused Vibration And Shafting Stability Of Supercritical(Urtrasupercritical) Turbine Generator

With the increase of turbine generator capacity and the improvement of operation parameters,the requirements of reliability and safety during operation are also increasing.However,the steam-indused vibration of supercritical(urtrasupercritical)turbine generator occur frequently.Due to the fact that steam-indused vibration is closely related to the load of generator,it will limit the load capacity of the unit which means that the safety and efficency will be influenced at the same time.The steam force in steam seal is one of the main factors which cause the steam-indused vibration.The calculation of the flow field in the seal is the basis of the study of the steam flow force.In this paper,the high pressure shaft seal of a 600 MW supercritical steam turbine generator produced by Shanghai steam turbine company is studied.The three-dimensional model of the shaft seal is established and the flow field in the clearance of seal is simulated by CFD method.The results show that the steam flow in the seal will produce a tangential force on the rotor which will reduce the stability when the rotor is eccentric.The dynamic characteristics of steam seal are utilized to evaluate the influence of steam seal on the stability of rotor.In this paper,the model of the caculation of dynamic characteristic coefficient of steam seal based on RBF neural network is proposed due to the complex calculation of large steam seal with CFD method.The calculation results show that the model can improve the calculation efficiency of steam seal dynamic coefficient in some extent and the calculation accuracy is enough to meeting the reguirements of engineering.It provides convenience for the analysis of the influence of the steam flow force on the stability of the rotor.The engineering experiences show that the steam-indeced viberation is closely related to the load and the low-frequency vibration is the other feature of it.The Jeffcott rotor is taken as the object of study to analys the feature of steam-indused viberation and MATLAB is used to simulate the motion characteristics of it when the rotor is under the action of steam flow force.The results show that the steam flow force will cause the low frequency vibration of the Jeffcott rotor and the frequency is consistent with the natural frequency of the first order modal.The three-demendional model of the rotor of a 600 MW steam turbine is established and the influence of steam flow on the stability of rotor is numerically simulated with Samcef which is a famous finite element software.The results show that the stability decreases with the increase of load and the rotor vibrates in low frequency which is close to the first order critical speed of rotor if the the shaft is instable.