The working principle of mechanical seal gas film seal (2)-

The working principle of mechanical seal air film seal (2)

　2017-10-11　　

The working principle of mechanical seal air film seal (2):

Figure 3-5 shows the analysis of the force of the spiral groove gas film seal when the gas film thickness changes. It can be seen from the figure that during normal operation, the closing force and opening force (air film force) of the seal are in a balanced state (under ideal design conditions). When the sealing gap is reduced by external interference, the gas film pressure on the end surface rises rapidly, and the efficiency of the spiral groove opening the gap increases, making the opening force greater than the closing force, forcing the end surface to return to the original state; on the contrary, when the external interference increases, The air film pressure in the gap drops, so that the opening force is less than the closing force, and the sealing surface gap is reduced and restored to the original state. It can be seen that the gap recovery mechanism of the air film seal ensures a good followability of the compensation ring under the action of the spring to the axial displacement, angular displacement or deflection of the non-compensation ring.

In the air film seal, it is necessary to ensure that the sealing end face has sufficient opening force and air film rigidity. The air film seal must increase the hydrodynamic pressure effect on the basis of the hydrostatic pressure. The increase of the hydrodynamic pressure effect is through the sealing end face It is achieved by machining a fluid dynamic pressure groove; at the same time, the fluid dynamic pressure groove has the function of providing and controlling the gas film hydrostatic effect and the dynamic pressure effect. Therefore, the gas film seal is considered to be a hybrid seal with both static pressure effect and dynamic pressure effect.

Fluid dynamic pressure groove There are many types of fluid dynamic pressure groove. The typical unidirectional groove and two-way groove structure are shown in Table 3-2.

Table 3-2 Typical structure of fluid dynamic pressure tank

Figure 3-5 Analysis of the force of the spiral groove gas film seal and the change of the seal gap when the gas film thickness changes

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