Functional analysis on the component unit of typical bi-directional groove dry gas seal

Based on analyzing the structural characteristics of typical bi-directional grooves of dry gas seal, the three basic component units of the bi-directional groove are presented, including the radial inlet groove and the symmetric arrangement hydrodynamic grooves, which are located upstream and downstream, respectively. Based on gas lubrication theory, the geometric model and mathematical model of dry gas seal with typical bi-directional groove are established. The gas film pressure control equations are resolved by use of the finite difference method, and the influence of basic component units of typical bi-directional grooves, including radial inlet groove and the symmetric arrangement hydrodynamic grooves, on sealing performance of dry gas seal are analyzed at the condition of high speed. The function mechanism of basic component units on sealing performance is discussed. The results show that radial inlet groove is important in enhancing film stability and load capacity. The film stiffness and opening force of dry gas seal with the radial inlet groove are much larger than those without the radial inlet groove. The upstream hydrodynamic grooves have significant effects on film stiffness and opening force, while the downstream hydrodynamic grooves have significant effects on leakage rate and opening force. To obtain larger stiffness and opening force, the optimal design of row number in the radial direction of hydrodynamic grooves is essential.