Leakage Characteristics and Parameters Influence of an Axial Laminate Pumping-out Groove Dry Gas Seal

In order to improve the sealing performance of dry gas seal, which is difficult to form gas film at low rotating speed due to weak hydrodynamic effect and easy to form large gas film thickness to cause excessive leakage at high rotating speed, a novel type of dry gas seal structure with axial laminate pumping-outgroove was proposed by setting up a pumping-out groove inside the rotating ring and connecting with the end of pump-in groove through the diversion holes. The principle of the novel seal structure was to utilize the dynamic pressure effect of the pumping-in groove on the end face to strengthen the gas film bearing capacity, while the pumping-out groove could reverse the sealing gas on lower-pressure side to the higher-pressure side to reduce the leakage rate. The flow field and steady-state performance of the dry gas seal were simulated based on the commercial software ANSYS Fluent. The steady-state performance of the axial laminate pumping-out groove, classic spiral groove and herringbone groove dry gas seal were compared, and the qualitative influence rules and quantitative correlation model among the leakage rate, reflux rate and rotating speed, outer pressure, and gas film thickness of the axial laminate pumping-outgroove seal were studied. The key structural parameters and their optimal values of the axial laminate pumping-out groove structure were discussed. The results showed that compared with the classic spiral groove gas seal, the opening force of the axial laminate pumping-out dry gas seal was increased by 5% at zero speed, and the leakage rate was reduced by 35% at high speed. The opening force was not sensitive to the change of rotating speed, and the leakage rate decreased slightly with the increase of rotating speed. It was a sealing structure with excellent characteristics of high gas film bearing capacity at low speed and low leakage rate at high speed. It was suitable for high rotating speed and small film thickness conditions. The reflux pumping capacity of the axial laminate pumping-outgroove was affected by rotating speed, outer pressure, and film thickness.The positive or negative of the reflux flow rate, which was an index to measure pumping capacity of the axial laminate pumping-out groove seal, was mainly determined by the rotating speed, while the value of the reflux rate was mainly affected by outer pressure. In addition, the reflux pumping capacity was also related to the geometric parameters of the axial laminate pumping-out groove dry gas seal, it was mainly affected by the depth and spiral angle of the pumping-out groove and radial location parameter of diversion holes. When the pumping-out groove depth 0.1 mm<h_r<0.4 mm, the spiral angle 10°<α<20° and the radial location parameter of diversion holes 0.11<R<0.23, the axial laminate pumping-out groove seal hads an excellent property with good pumping-out capacity and low leakage rate.