Study On Steam-Induced Vibration For Supercritical (Ultra Supercritical) Turbine

As the 13th Five-Year plan has been introduced,The government's demand for energy conservation and environmental protection is further strengthened, which means a greater challenge to the power generation industry in saving efficiency and reducing energy consumption.Therefore, more and more super critical (Ultra super critical) turbines with large capacity and high parameters have replaced the small capacity turbines. According to "2015 China Electric Power annual development report", by the end of 2014,600MW and above units accounted for 41.58% of the country's thermal power unit capacity and become the main force of generating units. However, large capacity and high parameters also lead to the increasing of the steam-induced vibration fault. At present, the steam-induced vibration has become one of the main problems which affect the stable operation of large steam turbine units. Therefore.it is very necessary to research the steam-induced vibration of the supercritical steam turbine, present the method to restrain the vibration and avoid the occurrence of steam induced vibration.The main reasons for the steam-induced vibration fault are the generation of the steam excitation force and the reduction of the stability of the rotor-bearing system.In this paper, the author starts from these two points, used the CFD method to calculate and analyze residual steam force in the different conditions, different valve sequences, used the method of mathematical calculation to analyze the blade-tip clearance excitation force, and then analyzed the dynamic parameters of bearing under the influence steam-induced excitation force. Finally, the author established finite element analysis model of rotor-bearing based on the 660MW supercritical steam turbine, and studied the dynamic characteristics of the rotor-bearing under the influence of different conditions in detail.The results obtained from this paper shows:the blade-tip clearance excitation force will further increase the working frequency vibration of the rotor, which is detrimental to the operation of the unit; when the turbine using nozzle governing steam, the working frequency vibration of the rotor is always increased, but the amplitude increment of vibration is different when valve orders are different. In some valve orders, the steam force reduces the bearing load or makes the rotor deviate from balance position, the log decrement of the rotor-bearing system is low, so it is easy to cause the steam-induced vibration fault; When the valve oder is reasonable, the rotor vibration amplitude increases in a reasonable range, and the stability of the system increases. The results of this paper are used in the real unit with the steam-induced vibration fault, and the steam-induced vibration is well suppressed.