Characteristics And Instability Analysis For Spiral Groove Dry Gas Seal Based On Fluid-solid-heat Coupling

It is the key point to ensure reliable and safe operation of gas seal system to keep the dynamic stability of the gas film. The stability of the face seal film is closely related to its temperature and dynamical characteristics, from four aspects:thermal fluid nonlinear dynamical analysis of gas seal system, instability analysis of axial for the dry gas seals system, instability analysis of angular wobbly for the system, experimental validation, the safe operation conditions of the system are analysized form different angles, the accuracy of the mode and the numerical calculation are proved through experiments.First, thermal process of the lubricated gas film for the system was stadied based on the thermal hydrodynamics theory, the thermo-elastic deformation of the seals ring caused by the heat of the system and its effect on the seal properties are analysized. The pressure distributions function is obtained not considering the seal rings’ deformation based on the Reynolds equation under the slid boundary conditions, the entropy variation equations of fluid in the spiral groove are derived and the temperature field distributions of the gas film are obtained. The temperature distribution of the gas film under the different polytropic exponent is analyzed considering the process of entropy change of the fluid in the spiral groove. The thermo-elastic deformation of the seal rings and the approximate analytic of the gas film thickness is obtained under the different polytropic exponent, the theoretical leakages considering and not considering the thermo-elastic deformation are obtained, then compared with the experimental measurements, the leakage by using the different polytropic exponent is closer to the experimental measurements than the theoretical value.Secondly, nonlinear stability of axial for the system was studied based on the nonlinear vibration theory. A fluid-structure interaction dynamic model of axial vibration of the system was established, the vibration equation was solved and the nonlinear dynamics behavior of the instability point was analyzed. Instability point-fields is obtained using the numerical method, the chaotic motion was found under the specific spiral grooved parameters of the structure, and then the chaotic motion was controlled by select reasonable parameters. Nonlinear forced vibration differential equation contains the second and the third order was derived while the nonlinear axial rigidity of the gas film was calculated and simulated, The bifurcation question was discussed according to solve the Floquet exponent unconsidering the outer excitation, and the stability influenced by spiral angle was analyzed in the system, the range of the spiral angle enable system stable was given.Again, nonlinear stability of angular wobbly for the system was studied. The dynamic model of the angular wobbly of the system was established, and the angular wobbly two-dimensional vibration equations were solved, then instability parameters of the system were obtained, quantitative relation of critical moment of inertia and the angle and the nonlinear dynamic behavior of the instability point was analyzed, parameters of the structure enable system stable is obtained also. The dynamical angular wobbly vibration model of the gas film and seal rings in the system of dry gas seals was established, a nonlinear forced vibration differential equation contains the second and the third order was derived while the rigidity of the gas film is expressed as a variable containing the swing angle, The bifurcation question was discussed according to solve the Floquet exponent unconsidering the outer excitation, and the stability influenced by spiral angle was analyzed in the system, the range of the spiral angle enable system stable was given.At last, the experimental investigation of dry gas seal prototype was conducted on the sealing test device, and the overall plan design and the hardware configuration of the test system is proposed. Leakage, gaseous film axial rigidity and sealing ring axial vibration displacement are tested, test results are obtained and the error between test and calculation data is analyzed.The results show that dynamical and mathematical model for the system of gas film and seal rings of the spiral groove dry gas seal is validated correctly comparing the data from experiments with the approximate calculation, and the developed program of approximate analysis method is practicable.