Performance Analysis And Modification Investigation Of A T-groove Dry Gas Face Seal

A dry gas seal with T-grooves onto its faces (T-DGS) has the ability of bi-directional rotation, so it has been widely used in the rotating equipment applications such as high-speed centrifugal compressors, gas turbines and rurboexpanders. The failures of such a T-DGS have been appeared occasionally in the fileds because of our lack of understanding the stable operating conditions and failure mechanisms of a T-DGS. In addition, the insufficient of load capability and stability of a T-DGS compared with that of a spiral-grooved DGS is one of the main factors of such failures, and it is also the main factors of limiting their applications to further expand.A mathematical model of a T-DGS is established based on gas lubrication theory, then the finite element program was written by use of Matlab to solve the model. By calculating the seal performance parameters, and compared the calculated results with the experimental results in the open published literatures, the model is proved to be correct, and the rationality and reliability of calculation method is confirmed. On this basis of the above work, the effect of rotational speeds and sealed medium pressures on geometric optimization of T-grooves is analyzed. The results show that rotational speeds and sealed medium pressures have great effect on the optimization values of face geometric parameters. The optimum value charts of geometric parameters of T-grooves under different rotational speeds or sealed medium pressures are provided. The rotational speeds have great effect on the geometric parameter optimizations of circumferential ratio α1, width ratio α2and depth hg of T-grooves, but have little effect on the geometric parameter optimizations of radial ratio β1and length ratio β2of T-grooves. The sealed medium pressures have great effect on the geometric parameter optimizations of circumferential ratio α1, radial ratio β1and depth hg of T-grooves, but have little effect on the geometric parameter optimizations of width ratio α2and length ratio β2of T-grooves. Finally, a new type of T-DGS with tapered-depth T-grooves onto its faces is introduced in order to improve the hydrodynamic effects and stability of a general T-DGS. The seal performance parameters are investigated compared with between the two types of DGS with T-grooves. The results show that the tapered T-grooves has better hydrodynamic effects and stability, especially under the operating conditions of both low rotational speeds or low sealed medium pressures and high rotational speeds or high sealed medium pressures this advantages are more apparent. On this basis, the face geometric parameters of tapered-T-groove were optimized mainly based on the principle of getting the highest levels of gas film stiffness.The results of this paper improved face groove design theory of T-DGS, and will provide strength theory guidance for range of applications expanding, life extending, stability and reliability improving of T-DGS in industrial applications. Thus, the value of this paper is great significance for theoretical and engineering applications.