Theory Of Thermodynamic Lubrication Of Floating Ring Textured Gas Film Seal Experimental Study

With the rapid development of modern industry,rotary machinery and equipment are widely used in many fields such as chemical industry and transportation,which greatly improves people’s quality of life.Under the current scientific development trend,reducing resource consumption and improving safety and reliability in the high-end equipment manufacturing industry have become important development goals to promote sustainable development.Although the air path system layout design of aeroengine has been quite perfect,improving the sealing effect of aeroengine has become an important direction of green development and research of aeroengine.Therefore,the research on the sealing performance of the floating ring gas film sealing system is of great engineering value for improving the running stability of the shaft end seal and reducing the leakage quantity,which also meets the needs of sustainable development.First of all,for the floating ring gas film seal structure selected in this topic,under certain assumptions,the pressure governing equation and film thickness governing equation of floating ring gas film seal are introduced and derived.Combined with the pressure boundary conditions,Newton-Raphson iterative method and finite difference method are used to solve the Reynolds equation and the gas film thickness equation.The lubrication gas film pressure distribution in the calculation domain is obtained.At the same time,this paper adopts rectangular micro-texture as a way to improve the sealing performance,explores the influence of working conditions and structural parameters on the sealing performance,takes the float leakage ratio as an indicator to judge the hydrodynamic lubrication performance of the surface texture,and uses the rectangular texture at the rotation Angle β=0° as the carrier for subsequent research.The results show that the increase of rotational speed and eccentricity is beneficial to improve the sealing performance,while the increase of pressure and texture depth will reduce the sealing performance.Secondly,in order to study the action mechanism of the flow regime on the air film seal of the floating ring,based on the turbulent Reynolds equation considering different bottom profile shapes and the established simplified energy equation of compressible fluid,the paper studies the influence law of the steady-state characteristics of the four bottom shapes under different working conditions and different flow patterns,and obtains the textured bottom shape which can ensure good sealing performance in engineering applications.The results show that the variation trend of steady-state characteristics in turbulent flow is basically the same as that in laminar flow,but the turbulent effect makes the pressure and temperature distribution in the gas film flow field change more significantly.Further,according to the above calculation results and the theory of fluid mechanics and solid mechanics,a circulation-heat-solid coupling model of floating ring gas film seal is established,which fully considers the effect of mechanical load,thermal load and other generalized external loads.Through numerical calculation,the deformation and flow field distribution of the seal pair were studied,and the effects of inlet pressure and rotational speed on the steady-state seal characteristics were analyzed.The results show that the effect of thermal effect on th e deformation of floating ring cannot be ignored,and the effect of thermal coupling is basically the same as that of single thermal load on the sealing ring.The floating ring gas film seal exhibits excellent static sealing performance under the operating conditions of low pressure,high speed and small film thickness.Finally,in order to verify the accuracy of the numerical calculation results in the paper,the sealing performance parameters were tested under different working conditions through the self-built floating ring gas film seal test system,and the test results were summarized and analyzed.Through comparative analysis and theoretical values,it is found that the change of speed and pressure will cause the change of gas film flow field,and then reflect the influence on the sealing performance.Under low speed and low pressure conditions,the internal flow of the gas film follows laminar flow law.However,with the increase of rotational speed and pressure,the gas film flow will change into turb ulent flow,and the turbulence effect has a significant influence on the steady-state characteristics.Compared with isothermal flow,the flow of gas film is closer to adiabatic flow under the same working condition.The good agreement between the theoreti cal calculation model and the experimental results shows that the theoretical model has good reliability.In order to verify the numerical results of the paper,a floating ring gas film seal test system was built,the high-speed test bench and the air road system were modified,a new type of seal system was designed,and the seal performance parameters were tested under different working conditions.The experimental and theoretical values are compared and analyzed.The results show that the change of speed and pressure can cause the change of the flow field in the gas film,which reflects the influence on the sealing performance.Under low speed and low pressure conditions,the flow in the gas film follows laminar flow law.With the increase of rotational speed and pressure,the flow in the gas film will change into turbulent flow,and the turbulence effect has a significant influence on the steady-state characteristics.Compared with isothermal flow,the flow in the gas film is closer to adiabatic flow.The good agreement between the theoretical calculation model and the experimental results indicates that the theoretical model has a certain reliability.In this paper,the flow field distribution,steady-state performance and dynamic characteristic coefficient of the floating ring gas film seal under the action of multiple complex effects are systematically described by the method of theoretical modeling and experiment,and the sealing performance considering the coupling deformation is considered.The researc h results of this paper have laid a solid foundation for the future floating-ring gas film seal in groove design,sealing characteristics analysis,engineering application and so on.