Dynamics Analysis And Optimization On SFD- Sliding Bearing System

The stability of rotary mechanical has direct relations to safe reliability of the unit. As high-speed and high-capacity units were brought into service, the research of stability relevant to units'accident revention has been a significant subject in the study of rotor dynamics. Damper is an effective solution to promote the stability of system and squeeze film damper based on film technique is widely used at the present time. System parameters have certain influences on dynamic features of SFD-sliding bearing system, however, not any squeeze film damper can increase stability and damping capacity of rotor system. The adequacy of parameter design may affect the matching degree among parameters. The optimization of rotor system is to make dynamic characteristics to achieve the best state. This paper comprehensively utilizes theoretical analysis and numerical stimulation to make a systematical research on dynamic response of SFD-sliding bearing system and dynamic optimization, gaining some research, as follows:(1) Based on Reynolds equation, this paper resorted to long bearing theory of Summerfield assumption to deduce oil-film forces of bearings and employed short bearing approximation theory of Summerfield assumption to further conclude the oil-film forces of SFD.(2) This paper established the mechanics model of SFD-sliding bearing rigid rotor system, provided its equation governing the equation of motion and adopted numerical analysis method to solve the differential equation, thus acquiring the dynamic response and critical speed of the system. The study has shown: from stable periodic motion, the rigid rotor system go through quasi-periodicity bifurcation and finally come to the state of chaos.(3) The paper took SFD-sliding bearing flexible rotor system as study object, adopted long bearing theory on sliding bearing, employed short bearing theory on SFD and established mechanics model of SFD-sliding bearing flexible rotor system based onπfilm assumption. Besides, the thesis utilized 4-5 order Runge-Kutta method to solve nonlinear differential equation, thus acquiring the dynamic response and resorted to 4-5 order Runge-Kutta method to get the first two critical speed of the system. The study has shown: from stable periodic motion, the route of the flexible rotor system to go into chaos is: periodic motion—quasi-periodic motion—chaos—period—doubling bifurcation—chaos. (4) After analyzing the sensitivity of flexible rotor system on the first two critical speed towards structural parameter, this paper came to the conclusion that the first critical speed is sensitive to oil viscosity, bearing clearance and SFD clearance while the second critical speed have high sensitivity towards SFD clearance, bearing clearance and shaft stiffness. The sensitivity analysis offers design variables to optimization analysis. Sensitivity analysis enables to improve the efficiency of optimization and shorten the design cycle.(5) On the basis of sensitivity analysis, this paper employed genetic algorithm to give an optimization analysis on critical speed under the conditions of constant speed and varying speed. The optimization objective is to remove critical speed from working speed as much as possible. After optimization, working speed of the system will ameliorate, far away from the critical speed and supply theoretical basis as well as theoretical analysis towards the dynamic stability of high-speed rotor system.