The Research On Nonlinear Dynamic Behavior Of The Spiral Grooved Gas Seals

The stability on a system of spiral grooved gas seal is closely related to its dynamical characteristic, and hence its dynamical characteristic has been the domestic and foreign research area. The paper takes spiral groove dry gas seal as research project,dynamical model on two degree of freedom system of gas film and seal ring subjected to axial vibration was established, and the axial vibration equation was solved by using the Maple program , then the static ring following-up ring's dynamical characteristic has been analyzed, on the basis, a nonlinear forced vibration differential equation was derived while the nonlinear dynamical characteristic of the gas film was calculated and simulated, and the stability influenced by spiral angle was analyzed in the system. The main contents and achievements are summarized as follow:Calculation model on a system of axial damper and angular damper coefficient, and the approximate function expression of damper coefficient were solved by using the Maple program, and the approximate solution of gaseous film rigidity was obtained. Finally optimizing geometric parameters under environment pressure and speed were acquired by analyzing the dynamic stability. The results show that with the increase of environment pressure and speed, damper coefficient increases and then got the finally optimizing geometric parameters that the basic agreement of experiment date. So calculation model on a system of damping coefficient is correct, which provides the theoretical basis on dynamical optimization design of gas seals.The dynamical model of dual freedom degree of gas film-seal ring system under axial vibration was established. The axial vibration equation was solved by using the Maple program, then the time history charts of stationary ring with various following-up coefficients were obtained. The results show that the critical condition of stationary ring following rotating ring is that spring rigidity value is 0.42 times greater than gas film rigidity value. The critical condition remains unchanged with changing operating parameters, but it changes with the change of structure parameters. The stability of gas film can be controlled by selecting suitable following-up coefficient, which may provide the theoretical basis for the dynamical optimization design of gas seal.The dynamical axial vibration model of the gas film and seal rings in the system of dry gas seals was established that the help of the theory of nonlinear vibration, a nonlinear forced vibration differential equation was derived while the nonlinear dynamical characteristic of the gas film was calculated and simulated, in order to obtain the Melnikov function, the free oscillation equation of a kind of nonlinear dynamics system was solved, an exact solution to the problem was obtained under varying initial conditions. The bifurcation question was discussed according to Floquet exponent, and the stability influenced by spiral angle was analyzed in the system, the range of the spiral angle enable system stable was given on the condition of none outer excitation, when spiral angleαat 75°10′14″the Hopf bifurcation occurs in the system. Regions of structure parameters enable system stable was obtained, the result guiding the dynamic optimization in the dry gas seals system.The experimental investigation of groove dry gas seal was conducted on the 2900r/min test device in ChengDu YiTong Seal Co., Ltd. The research finished overall plan of instrumentation system and hardware configuration, tested leakage, power lose and gaseous film rigidity, obtained test results and analyzed error between test and calculation data. Comparing some data from experiments with that of approximate calculation, the results show that dynamical and mathematical model of the gas flow between seal faces is validated correctly.