T Groove Dry Gas Seal Dynamics Performance

Dry gas seal another name is mechanical gas film seal. Dry gas seal is a kind of new non-contact mechanical seal. Dry gas seal have the advantage of a little friction, low leakage rate, long running period, using widely for shaft seal in high speed and high pressure running fluid machinery of petroleum chemical industry during the recent years. However, the theory study of dry gas seal lagging behind the using in production, lacking full and total dry gas seal theory conduct the use of dry gas seal. The T-groove dry gas seal has a symmetric structure of the groove geometry, which adapt the condition of rotate bi-directionally. Now, the research on the dynamics performance of the T-groove dry gas seal is relatively little. Therefore, in this paper the theory of T-groove dry seal dynamics performance was studied, and gotten the law of various factors.The study of T-groove dry seal dynamics performance was based on the steady state and the gas film dynamic performance. Although the steady state of dry gas seal has studied deeply, but the real gas effect was often ignored. In this paper, the effect of real gas was discussed, where the virial equation of state expresses the effect of real gas, and the finite difference method (FDM) was adopted to discretize the steady equation of gas lubrication. The effect of real gas on T-groove, radial Groove and spiral-groove was analyzed and discussed in opening force and leakage rate.The gas film dynamic performance of T-groove has some study but not deeply.In this paper, the gas film dynamic equation was deduced in detail, then using the way of the small perturbation method solved the axial gas film stiffness coefficient and axial gas film damping coefficient, and the difference scheme was given and some examples were checked the scheme. The effect of real gas was discussed on the example of CO2, H2, and N2. The curves of stiffness and damp of gas film were fitted respectively in specific parameters, gotten the equation of gas film stiffness and the equation of gas film damp.In this paper, the model of dry gas seal axial dynamics performance including the rotating ring and static ring two degree of freedom was built and solved using complex mode theory. The results of the free vibration and rotating ring subjected harmonic excitation were analyzed, gotten the rotating ring and static ring oscillation equation respectively and the variation equation of gas film thickness.The effect of the elastic supporting stiffness, the elastic supporting damping, gas film equilibrium position, the mass of the rotating ring and static ring and the mass ratio of the rotating ring and static ring were analyzed on T-groove dry gas seal. The results show:adjusted the elastic supporting stiffness, the mass of the rotating ring and static ring, the mass ratio of the rotating ring, the mass ratio of seal rings can influence vibration frequency of the rotating ring and static ring; adjusted the elastic supporting stiffness, the elastic supporting damping, the mass of the rotating ring and static ring, the mass ratio of the rotating ring, the mass ratio of seal rings can influence vibration amplitude of the rotating ring and static ring; adjusted gas film equilibrium position, the mass of seal rings and the mass ratio of seal rings can influence the variation amplitude of gas film thickness; adjusted the mass ratio of seal rings can influence vibration frequency of gas film thickness.