Study On The Catastrophe Performance Of The Steam Flow Excitation Vibration In Large Steam Turbine Governing Stage With Partial Admission

This study was supported by the National Natural Science Funds--Prediction researchon Nonlinear Rotor System of the rotating machinery catastrophe faults (fund number:50975105).Steam flow excitation of large steam turbine operation is an unstableself-excited vibration which is the most likely to occur in high and medium pressure rotor.Modern large steam turbine parameters are gradually improved and capacity is increasing.steam flow excitation harm caused by steam flow force is more severe, so that the turbinecan’t operate safely. This article establishes mechanical models and nonlinear dynamicequations of rotor for the steam flow excited vibration problem of steam turbine under partload when the governing stage is in an asymmetric inlet, and uses catastrophe theory toanalyze and study the fault.This work mainly consists of the following two parts:Part one: this part is for the steam flow excited vibration problem of steam turbineunder part load when the governing stage is in an asymmetric inlet. According to dynamicand static excitation force model, the dynamics equations of rotor system are proposed. Thecatastrophe manifolds and bifurcation set of system are deduced by catastrophe theory.Catastrophe impact factors are identified. The relationships between catastrophe amplitudeand impact factors are discussed. The results show: Changing in rotational angularfrequency, eccentricity, governing stage opening level and other system parameters maycause system vibration state mutation, and ultimately lead to failure of steam excitation;with the rotational angular frequency and opening level increasing, the eccentricity range ofmutations also increases, which means that flow excited vibration is more sensitive foreccentricity; moreover, with the flow increasing, the system will occur steam flowexcitation at a lower speed and smaller eccentricity. Finally, numerical method isemployed to verify the results.Part two: this part considers the impact of dynamic force on steam flow excitationfailure with partial admission and establishes rotor-bearing system dynamics equations. Thevibration bifurcation diagram is obtained using numerical methods when parameters of coupled system change, and the impact of these parameters on the stability of the wholesystem of movement is analyzed. The results show: with the opening level increasing,system stability is reduced; with the shaft stiffness, bearing length, the bearing radiusincreasing, system stability is enhanced; choosing bearing clearance, the valve open way,the number of open and opening size reasonably can improve the stability of the system.The research results has some reference value for the prediction and diagnosis of thesteam flow excitation and laid the foundation for further research on other faults of largerotating machinery rotor system by using the catastrophe theory.