Percolation interpretation of film pressure forming mechanism of mechanical seal and calculation method of film pressure coefficient

Abstract

The conclusion that the film pressure coefficient is inferred from the existing film pressure coefficient calculation method based on the assumption of microleakage at the sealing interface is about 0.5 seriously affects the accuracy of the mechanical seal contact pressure design. The composition of the fluid film pressure between the contact mechanical sealing interfaces was analyzed from a microscopic point of view, the formation mechanism of the film pressure is explained based on the percolation theory, and the fractal parameter calculation model of equivalent rough contact surface was proposed. The fluid-infiltrated sealing interface area on the inside and outside of the sealing line is discussed and determined, and a calculation method for the film pressure coefficient of the contact mechanical seal based on the percolation theory is established, and its correctness is verified by theoretical analysis and numerical simulation. The research shows that the film pressure coefficient can be determined by the calculation method of the film pressure coefficient established in this paper regardless of whether the sealing interface is leaky or not; the film pressure coefficient is related to the morphology parameters and the porosity of the sealing interface. For the four groups of rotating and stationary rings seal end face groups with different morphology parameters given in the paper, when the porosity is between 0 and 0.312, the film pressure coefficient is between 0 and 0.0547; when the porosity is between 0.312 and 0.593, the film pressure coefficient is between 0.0547 and 0.1791; at the initial porosity, the film pressure coefficient reaches 0.5374. The research results provide a theoretical basis for mechanical seals’ design and engineering application.