Nonlinear Vibration Characteristics Research On Labyrinth Seal Rotor System

Rotor system is an important part of large rotating machinery (such as the generator set, hydroelectric generating set, nuclear power generating units, air aerospace engines and indus-trial compressors, etc.). Gas dynamic excitation is an main factor to threat the rotating ma-chinery safety.In the aircraft engine, labyrinth seal is widely used as an effective gas seal, which mainly used for compressor, turbine stage, at the top of the leaves, the cooling flow path system, gas separation and oil and gas isolation in seal system of main bearing oil chamber. It is difficult to avoid biasing in a sealed cavity, once it happens, Seal excitation force will appear because of the uneven pressure. The disturbance and sealing of the rotor flow interacts with each other, sealing excitation force is nonlinear characteristics.In certain conditions, the rotor system can be excited by labyrinth seal force, which will cause the self-excited vibration of the rotor sys-tem.This paper mainly studies the rotor system nonlinear vibration problems caused by gas seal force. At first, the rotor system dynamics equations with Muszynska seal model is estab-lished, using numerical calculation method to simulate the system nonlinear vibration. Then based on the theory of CFD software FLUENT, numerical calculation of two-dimensional and three-dimensional of labyrinth seal flow field is done, and further calculate dynamics charac-teristic coefficient of the rotor system with the effects vapor seal and analyze its stability.1. The rotor system with seal structure of is simplified, introducing Muszynska seal model, establish the rotor system dynamics model and its dynamic equation.2. Numerical simulation of the rotor system vibration with Muszynska seal force re-sponse is done using fourth-order Runge-Kutta method, compare the frequency domain chart, axis path chart and the Poincare sections chart, research the nonlinear vibration characteristics of rotor system under the imbalance of excitation force and sealing force in different speed, different pressure differential and different seal clearance of. Numerical simulations show that the rotor system will appear period, period-doubling, quasi-period nonlinear vibration.3. Based on the theory of CFD, using FLUENT to calculate the two-dimensional flow field of the labyrinth seal, get the two-dimensional flow characteristics of labyrinth seal, proving the labyrinth seal throttle effect.4. Labyrinth seal three-dimensional flow field are analyzed with FLUENT, and calculate the labyrinth seal force at different speeds, different pressure ratio, thus further calculate the dynamic characteristic coefficient of the labyrinth seal rotor system, and analyze the stability by using the vortex frequency coefficients.This work has the vital significance on the vibration analysis of rotor system with the gas seal structure.