Study On Self - Aligning Mechanism Of Spiral Groove Dry Gas Seal And Its Realization

Spiral groove gas seal has been widely applied to various occasions because of its excellent properties, and the requirement of its working stability is becoming higher and higher. Under the influence of temperature and pressure, the deformation of the static ring with lower elastic modulus happened and the convergence or divergence gas film formed at the end of the ring, thus affecting the sealing performance. Based on this situation, Josef Sedy put forward a self-aligning mechanism for the spiral groove gas seal, which could decrease the force or deformation caused by temperature and improve the stability of operation of spiral groove gas seal, but now the research about self-aligning mechanism couldn’t be seen more. The research about a self-aligning mechanism for the spiral groove gas seal and its implementation way was done in this paper.The deformation of the static ring with spiral groove gas seal face happens, the distribution of pressure of face gas film would changed, and a self-aligning mechanism was completed right through this pressure distribution. Based on the theory of narrow groove, the distribution of pressure of face gas film of the parallel of spiral groove gas seal face, the deformation of force, and the deformation of temperature, were obtained by using the approximately analytical method, and the change of distribution of pressure before and after the deformation of face was discussed and analyzed. When the deformation of face happened, the pressure of spiral groove bottom was increased, while the deformation of temperature occurred, the pressure decreased; the leakage of spiral groove gas seal was increased with face getting deformation.The essence of studying the self-aligning mechanism for spiral groove gas seal was studying the deformation of the static ring under the action of force. The theory of axisymmetric deformation of Biezeno annular parts was adopted to analyze and calculate the deformation of the static ring force. Considering the influence of contact stress of O-ring on the force deformation of seal ring during calculation process, found that the contact stress of O-ring had a bigger influence on the deformation of static ring.The distribution of gas film pressure changed with the static ring deformation, the changed gas film force was generated a restoring moment on the seal face, which is opposite to the direction of face deformation, and the restoring moment made the seal face being reversed recover to the parallel position. The calculation model of restoring moment for self-aligning mechanism was established, and the influence of operations parameters and geometric parameters of face on the restoring moment was discussed and analyzed. The results indicated that the ability of self-aligning for spiral groove gas seal was increased with the pressure of medium increasing, and decreased with temperature and rotational speed increasing. The increase of spiral groove depth and spiral angel decreased the ability of self-aligning for spiral groove gas seal, and the increase of ratio of seal dam width would increase the ability of self-aligning of the seal system. While the radius of cross section of the static ring was smaller, the ability of self-aligning stronger.The necessary condition of spiral groove dry gas seal to achieve the self-aligning is that the pressure between the grooves and the dam must be bigger than the sealed pressure. It was found that when the condition was achieved, the deformed gas film pressure distribution was changed greatly so that the net gas film force had greater value which can produce enough restoring moment to achieve the spiral groove dry gas seal self-aligning.