Stability Analysis Of The Rotor System Under The Gas Exciting Force

In order to improve the MTE performance, the MTE rotor rotational speed is high and its own weight is light, so it relatively increased that aerodynamic load and the effect of the gas exciting force caused by blade tip clearance enhanced gradually. At the same time, the ceramic bearings have no way to be satisfied with the MTE whose working speed is 40,000RPM, so the gas bearing is considered to be used at the speed. Therefore it is essential to carry out the research of the rotor system which is under the action of the gas exciting, gas bearing or the both coupling effect. The main content of this paper specifically for this three kinds condition, have been carried out as follows:Firstly, stability model of rotor system which acting on the Alford force are analyzed. Subsequently, the dynamical modeles of the single-disc (compressor) and double-disc rotor system mounting compressor and turbine on a common axis are established using the FEA method. The stability of the two kind of rotor system is analyzed through the vibration response, which is obtained by numerically analysis with Runge-kutta method. The results indicate that the amount of unbalance, the rotor speed, supporting stiffness, damping, shaft span, position of the disc and static-eccentricity have significant influence on stability of the single-disc rotor system; The response of the rotor system having the compressor and turbine is relative complex, and the system may run steadily by adjusting the Alford on the two disc properly.Secondly, the finite difference method is employed to solve the Reynolds equation; furthermore the solving idea and calculation program are validated by an example. Subsequently, the gas film force is obtained by solving the transient Reynolds equation. A dynamic model of the rotor system supported by self-acting gas journal bearings was established, meanwhile the Runge-Kutta method was used to solve the equation coupling. Making use of the nonlinear dynamics theory,the nonlinear characteristics of a rotor system supported by self-acting gas journal bearings was studied through the system state trajectory, phase diagram, bifurcation diagram and power spectrum. The results show that rotor speeds and the amount of unbalance have great influences for the non-linear characteristics of the system, and many kinds of periodic and non-periodic responses exist in the system. Thirdly, elementary analysis of the non-linear characteristics of the system which is under the coupling effect of Alford force and gas bearing is carried out. Mainly the effect of the Alford force on the rotor system's bifurcation characteristics is studied. The results show that large Alford force may lead the system to the chaos state, even to the instability state.