Mechanism of Deep and Shallow Groove of Mechanical Seals
Publication Date: 2018-06-05 14:13:00
Deep groove and shallow groove non-contact mechanical seals are belong to
the fluid dynamic pressure mechanical seals, the principle of action is not
the same, the following will be simple about the role of deep groove shallow
groove sealing mechanism.
1. Mechanism of shallow groove mechanical seals
Dry gas seal (typical shallow groove seal) is a kind of hydrodynamic and
static seal, in the presence of medium pressure, the force acting on the
seal is hydrostatic, and exist in the sealing rotation or static.
Fluid dynamic pressure only occurs in the case of rotating seal ring, At
this time, the shallow groove opened by the sealing surface will be sealed
gas axial suction, toward the sealing dam flow, and the sealing dam control
gas flow. As a result, the gas is compressed, causing the pressure to rise.
When the pressure rises, the elastic mounting surface is detached to form
the required gas film. The stable gas film not only seals the working
medium, but also lubricates the friction pair.
2. Mechanism of deep groove mechanical seals
The mechanism of deep groove mechanical seals belongs to the category of elastohydrodynamic theory, which is generally used for liquid seals. As there are circumferential grooves of 1-2mm on the sealing ring, circumferential wave degree and radial cone direction are generated on the sealing surface under the action of force deformation and thermal deformation, and the wave amplitude of wave degree is micron.
Under the traction of the rotary ring, due to the fluctuation of the flow boundary on the sealing surface, the viscous flows along the circumferential direction alternately experience convergence and divergence zones:
1. In the convergence zone, the fluid membrane generates a high fluid dynamic pressure, so that the circumferential wave degree formed by thermal deformation and force deformation can generate a static additional opening force;
2. In the divergence zone, negative pressure may be generated. Because the negative pressure that fluid can bear has certain limit, exceed this limit, the air that dissolves in liquid will be displaced, generation cavitation phenomenon. In addition, the radial taper formed by thermal deformation and force deformation makes use of hydrostatic effect to generate additional hydrostatic bearing capacity and increase the opening force.
