The Working Principle Of Shallow Grooves And Deep Grooves in Mechanical Seals
Feb 12, 2022
I. The mechanism of action of shallow groove mechanical seals.
Dry gas seals (typically shallow groove seals) are a combination of hydrodynamic and static pressure seals. When the medium pressure exists, the force acting on the seal is hydrostatic and exists when the seal is rotating or stationary.
The hydrodynamic pressure only occurs when the sealing ring rotates. At this time, the shallow groove opened on the sealing surface sucks the sealed gas circumferentially, from the outer diameter toward the radial component flows toward the sealing dam, and the sealing dam controls the gas. flow. Therefore, the gas is compressed and the pressure rises. After the pressure rises, the elastic mounting surface is separated to form the required gas film. The stable gas film not only plays the role of sealing the working medium, but also plays the role of lubricating the pair of motorcycles. This enables the gas seal to operate without wear in a fluid-lubricated, non-contact state.
II. The mechanism of action of deep groove mechanical seals
The mechanism of action of deep groove mechanical seals belongs to the category of elastohydrodynamic theory and is generally used for liquid seals. Because there is a circumferential groove of 1-2mm on the sealing ring, under the action of force deformation and thermal deformation, circumferential waviness is generated on the sealing surface, and the amplitude of the waviness is micron level.
Under the traction of the moving ring, due to the breaking of the flow boundary of the sealing surface, the viscous flow along the circumferential direction alternately experiences convergence and divergence zones:
1. In the convergence zone, the fluid film generates a high hydrodynamic pressure, so that the circumferential waviness formed by the thermal and force shapes can generate a static additional opening force;
2. In the diverging zone, negative pressure may be generated. Since the negative pressure that the fluid can withstand has a certain limit, beyond this limit, the air dissolved in the liquid will flow out, resulting in cavitation.
In addition, the radial taper formed by thermal deformation and force deformation utilizes the effect of hydrostatic pressure to generate additional hydrostatic pressure bearing capacity, which increases the opening force.
