A radial segmented seal is composed of three or six carbon segments that are assembled by a circumferential (garter) spring that presses them against the rotor. Assembled, they take the form of an annular ring. Each segment has several pads that generate a radial lift force depending on the rotor speed. There are many ways of creating effective lift forces. For example, a pocket on the pad creates a lift force because each pad will act as a Rayleigh step bearing. A groove on the rotating shaft will also create a radial lift force on the pad. However, this latter lift force will be unsteady. The aim of the present work is the numerical study of the lift created by a grooved rotor on a pad. Due to the very small operating radial clearances of radial segmented seals (less than 10 μm), the problem can be simplified by analyzing a single pad and a grooved runner. Previous analysis of gas face seals or thrust bearings always considered grooved pads and a smooth runner, even when the runner was grooved. The peculiarity of this study, which is the first of its kind, is considering the unsteady problem of the moving runner grooves. The analysis was performed for a single pad of a radial segmented seal operating with air.

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