Fluid dynamic pressure type mechanical seal-

Fluid dynamic pressure type mechanical seal

　2017-09-25　　

Fluid dynamic pressure type mechanical seal:

The working principle of the fluid dynamic pressure mechanical seal is that when the seal shaft rotates, the lubricating liquid produces a fluid wedge dynamic pressure on the seal end face to squeeze between the end faces, creating a layer of end face fluid film to provide sufficient lubrication and cooling to the seal end face . The groove can be on the moving ring or the static ring, but it is best to open on the more wear-resistant ring of the two rings. In order to prevent impurities from accumulating in the groove and entering the sealing gap, if the leakage fluid flows from the inner diameter to the outer diameter, the groove must be opened on the static ring; on the contrary, it should be opened on the moving ring. Figure 3~2 is a typical structure of fluid dynamic pressure mechanical seal.

Figure 3-2 Typical structure of fluid dynamic pressure mechanical seal

Figure 3 (a) The seal ring with an eccentric structure is to make the center line of the end surface of one of the moving or static rings offset a certain distance from the axis (whether it is a moving ring or a static ring, The eccentricity refers to the narrower end face width of the two rings (that is, the ring with the boss), so that the ring continuously brings lubricating fluid to the sliding surface for lubrication when the ring rotates. The disadvantage is that the size is relatively large, and the load acting on the seal ring is asymmetric. Figure (b) The seal with an elliptical sealing ring is to make the end surface of one of the moving or static rings into an elliptical shape. Due to the action of the lubricating wedge and the tangential flow, a hydrodynamic fluid can be formed between the sealing end surfaces membrane. The circulation and cooling of the liquid can very effectively maintain the existence and stability of the lubricating wedge. Figure (c) The radial groove shape of the sealing ring with a radial groove structure is 45. The bevel is rectangular, triangular or other shapes, and the fluid film pressure between the sealing end faces is generated by the fluid itself. The radial groove structure forms a lubrication and pressure wedge between the end faces, which can effectively reduce the contact pressure of the friction surface, the friction factor and the temperature of the friction pair, thus improving the sealing pressure, speed limit and cooling effect. The disadvantage is that the liquid circulation is insufficient and the edge area of u200bu200bthe groove is not cooled well; the dirt particles trapped in the groove are easy to enter the gap of the sealed end face. Figures (d) and (e) have a circulation groove structure. The sealing end of the seal ring is an arc-shaped circulation groove. Because it can suck liquid, the outer edge of the seal ring is well cooled; it also has the ability to remove impurities and interact with the steering Irrelevant, reliable work. The hydrodynamic effect is formed in the seal ring itself. When the seal ring rotates, the groove can make the liquid cool down the seal face far away from it quite strongly. When this cooling is performed, a hydrodynamic wedge and a high-pressure zone are formed on the initial end surface of the seal ring with the same number as the number of grooves. Due to the tangential flow and pressure drop, a lubricating piece is formed behind each groove. Figure (f) The structure with a spinner is suitable for one-way rotation, the fluid film has a large rigidity, a large end face gap, and a small temperature rise, but it is not suitable for two-way rotation.

At present, the widely used sealing end faces are arc-shaped cyclic rings, sealing rings for external pressure and internal pressure, and spiral groove structures.

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Fluid static pressure type mechanical seal 　　 air film seal of mechanical seal