Effect of axially grooved oil seals on the leakage flow and stability of a centrifugal compressor

The results of an analytical investigation are given for the effect of axially grooved floating oil ring seals on the leakage flow and stability of a centrifugal gas compressor. The finite element method was used to solve the non-linear and coupled hydrodynamic and thermal equations for pressure and temperature distributions in the oil seal ring with and without the axial grooves. The peturbation technique was used to obtain the static and dynamic characteristics of the oil seal. The results for selected cases of axial grooving are presented in graphical form for operation at various eccentricities. The non-dimensional leakage flow results correlate well with previously published results calculated by narrow groove theory. The stability of a multi-stage gas compressor is evaluated for different configurations of the oil seal grooving geometry. The compressor rotor shaft finite element model includes a multi-level analysis for the oil seal rings that permits the evaluation of the floating seal influence on the total system stability. Results are given for both low and highpressure sealing conditions, which simulate test stand and field operating conditions. The results show that the added grooves enhance the stable operation of the rotor system for low-pressure fixed seal conditions and reduce the system stability at lower eccentricities for low-pressure floating seal conditions. In high pressure conditions the added grooves enhance the stability of the system for both fixed and floating seal conditions.