Numerical Analysis And Theoretical Prediction Method Of Interface Leakage Characteristics In Hard Sealing Structure

Sealing technology is widely used in modern industry, and some areas have strict requirements for sealing, such as petroleum, chemical, electronic, nuclear, aerospace and so on. At present, in the field of engineering application, the study of sealing technology mostly focused on the optimization and innovation of sealing structure, so as to improve the sealing performance and reliability of the equipment. But in the case of static seal, no matter how complex the sealing structure, there is a critical sealing surface on which any leakage occurrence. However, due to the existence of roughness, two sealing surfaces cannot be fully fit when combined, there will always be a leakage channels. Therefore, to improve the sealing performance of hard sealing structure should not only focus on the optimization of the overall structure, but the micro channel and flow characteristics of the interface leakage are analyzed and studied.In this thesis, based on the theory of stochastic processes, a two-dimensional digital filtering technique is used to generate a rough surface which satisfies the Gauss distribution and exponential autocorrelation function. The morphology of the rough surface can be adjusted by two parameters of the roughness and autocorrelation length, so rough surface with specific morphology characteristics can be generated.In order to study the effect of surface topography characteristics on the leakage rate, a geometric model of the leakage channel of the rough interface was constructed by using the 3D graphics software. Then, CFD software is used to calculate the flow field of the geometry model of the leakage channel, and the corresponding leakage rate is obtained. In order to study the difference between the leakage of the rough interface and the flat channel, this thesis introduced the flow factor, and the dimensionless fitting in the form of negative exponential function is carried out on flow factor.For the calculation of sealing clearance height, Roth model is adopted in this thesis. The model points out that the height of the seal gap is determined by the characteristics of the surface topography, the sealing load, mechanical properties of the sealing material and so on. In order to obtain the seal coefficient of the model, this thesis simulates the micro contact behavior of rough surface by using FEA software. And found that the sealing coefficient has nothing to do with the height of rough peak, but affected by the angular size of the rough peak.At the end of the thesis, the theoretical prediction model of the interface leakage is presented. Through the comparative analysis of the experimental data, the validity of the model is demonstrated. Using this model, the influence of the parameters on the leakage rate is analyzed, and some suggestions for improving the performance of the structure are also given.