The Logic Relationship between Macroscopic Characteristics and Mesoscopic Velocity Field of High-Speed Rotating Flow Field of Dry Gas Seal

Because of the complex fluid flow in the rotating flow field, especially under the high speed and micro scale conditions, the fluid flow state and its judgment methods were lack of a complete theoretical model. This paper chose the dry gas seal as the research object of high speed rotating flow field, with its opening force and leakage rate as index parameters of macroscopic property characterization. The shear (circumferential), radial and axial velocity components were used to give mesoscopic description of the velocity field. Fluent software was used to simulate and calculate the macro and mesoscopic parameters of large-span rotation speed (from low to ultra-high rotational speed), and the internal logical relationship between sealing performance parameters and velocity field was studied. The results showed that the axial velocity component in the low-speed rotational flow field was small and negligible, but the increase of rotation speed caused the axial velocity component to increase continuously. And when the rotational speed increased and exceeded a critical value, the axial velocity component increased rapidly. The variation of the axial velocity component was closely related to the fluctuation of the micro-scale flow field (the opening force and leakage). It is a key parameter that affected the flow pattern of rotating flow field and a main factor that caused the change of macroscopic flow field characteristics. The variation of the radial velocity component was basically consistent with the variation of the leakage in the microscale flow field. With the increase of the rotation speed, the macroscopic performance feedback of the leakage was earlier than the appearance of the opening force fluctuation. Based on the above research and according to the definition of Reynolds number of pipeline, the flow factor determination model and the basic theory of fluid mechanics, an ellipsoid determination model based on three-dimensional velocity component for the rotational flow field was proposed.