Bidirectional Trapezoidal Versus Unidirectional Spiral Groove Performance in Dry Gas Seals

Abstract

The gas film characteristics of bidirectional dry gas seals with trapezoidal grooves were studied by comparing with the traditional spiral grooved gas seals. The two-dimensional compressible Reynolds equation was solved by finite difference method. The typical performance parameters including gas film force, leakage, gas film stiffness, and torque were compared under different parametrical conditions. The pattern of trapezoidal grooves wasted part of groove area in bidirectional operation; though the grooves were designed by overlapping trapezoids to make up for the performance loss, the resulting decrease in gas film stiffness was notable. The resisting disturbance ability of trapezoidal grooved seals was poorer than that of spiral grooved seals, while the load-carrying capacity, sealing ability, and power consumption of trapezoidal grooved seals differed slightly from those of spiral grooved seals. The trapezoidal grooved seals are not recommended in unidirectional rotational compressors due to the decreasing stability.