Fluid - Solid Coupling Analysis Of Spiral Groove Dry Gas Seal

In the non-contact operation process of the spiral groove dry gas seal, the gas film flow and the seal ring deformation are mutually coupled. In order to reduce the number of assumptions of the dry gas seal study and improve the accuracy of calculation, and get more in line with the performance parameters of the dry gas seal in the actual working conditions, so as to provide a theoretical basis for the design optimization of dry gas seal. In this paper, The fluid structure interaction of spiral groove dry gas seal was analyzed and researched, where the theoretical analysis and numerical simulation were adopted, and also the Joule-Thomson effect was analyzed that occured when the seal gas got through the seal gap.Assuming that there are two kinds of parallel and inclined gas films, the theoretical analysis of the spiral groove dry gas seal was carried out by solving the gas film pressure equations. In the spiral groove dry gas seal, the mesh independence of numerical simulation was verificated, The sawtooth spiral groove and the common spiral groove dry gas seal have been selected as the examples, whose performance have been analyzed by the numerical simulation of the gas film flowing by Fluent, whose gas film pressure distribution, the opening force, the leakage and stiffness have been calculated respectively. According to the application conditions, the two grooves have own advantages and disadvantages.Assuming static ring deformation is axial symmetric and linear deformation, according to the structural parameters and operating conditions of the static ring, the force of static ring was analyzed, the deflection angle of static ring was calculated by the Piceno ring theory, namely static ring deformation. The results showed that the deformation of static ring decreases with the increase of the seal gap. When the film thickness was 2.03 μm, the maximum deformation of the static ring was nearly twice as much as that of the seal gap; when the seal gap was 2.6448μm, the maximum deformation of static ring is close to the seal gap. In the analysis of the spiral groove dry gas seal, the deformation of the static ring could not be ignored.Assuming the static ring deformation is axial symmetric and linear deformation, the gas film and static ring of spiral groove dry gas seal was theory analysis by the method of fluid structure interaction, the changing law was obtained that the change of gas film and the static ring deformation, namely minimum film thickness will be reduced and leakage will be increased, when the deflection angle increases.It is combined with Fluent and Mechanical software by ANSYS Workbench platform that numerical simulation of spiral groove dry gas seal by the method of fluid structure interaction. The theoretical and numerical solutions were compared and analyzed, the results showed that the analysis of the static ring deformation could use the total deformation instead of the axial deformation. The difference of maximum deformation were not very big, which were obtained by the fluid structure interaction numerical simulation and the theoretical calculation. It proved that the linear processing has certain guiding significance in the theoretical analysis of the static deformation, when the seal rings were all hard material, it is reasonable to assume that the seal rings does not deform in the dry gas seal. Otherwise there will be a large deviation.The Joule-Thomson effect will occur when considering the seal medium as real gas and the seal gas through the seal gap. As to the hydrogen, nitrogen, air and carbon dioxide, which are often met in the dry gas seal.The JT coefficient curves and Joule-Thomson inversion curves were made by the most suitable equation of state, and the gas temperature drop caused by the Joule-Thomson effect through applying the computer program, as to the air through the dry gas seal end faces. The results showed that the Joule-Thomson effect had important influence on the throttle of dry gas seal. At common temperature, the hydrogen shows thermal effect, but the nitrogen, air and carbon dioxide showed cooling effect.