Study On Nonlinear Dynamics Of Tilting PAD Journal Bearing-Rotor System

Rotor bearing system is the heart of large-scale rotating machinery, as a major way to support, the dynamic problem of tilting pad journal bearing (TPJB) growing concern by the people. Bearing instability problem of the rotor system is a major research topic of dynamic problem. Instability of rotor is main cased by nonlinear excitation force(oil film force, sealed, uneven steam force ) which producted by the tiny gap between the rotor and the bearing, so linear dynamics study of the rotor stability has many limitations, when the rotor as well as the operation of the corresponding cycle, bifurcation, chaos, and other unexplained phenomena. Therefore, the use of the theory of nonlinear dynamics research results combining rotor dynamics theory solve the problem of TPJB have a very important theoretical significance.Reasonable choice dynamic model is important to theoretical research of the TPJB. Parameter of pad which have great impact to stability should be reasonable selected. Based on this establish the dynamic model of five-pad TPJB which load on pad.The journal bearing oil film forces were obtained from database method, the nonlinear dynamic behaviors of rotor bearing system was investigated. And analysis two parameters of TPJB (pivot position factor and pre-load factor) have effect on system stability, the results showed: pivot position factor and pre-load factor in the low rotor speed have great effect, but with the increased speed, the effect of the two parameters decreased, after speed reach to natural frequency, the effect of the two parameter can be ignored.The nonlinear stability of the TPJB is investigated, based on Floquet theory and the shooting method, the primary parameters affecting its stability are unbalance, stiffness, speed. Show the process of TPJB change from cycle motion to chaos motion. The results show TPJB have three bifurcations: saddle-node bifurcation, doubling bifurcation, Hopf bifurcation. The studying deeply of TPJB still needs to do a large number of work, need to provide the taken method of all kind of nonlinear force, reducing dimension method of high-grader system, numerical calculation method which higher efficiency and so on. Developing nonlinear dynamics theory, solving concrete problem of nonlinear dynamics design of TPJB, and all kind of practicality problem for actual unit. This is one very difficult task in the studying nonlinear dynamics design.