A Rayleigh-Step Face Seal with Reverse Steps

This paper presents a new hydrodynamic seal, in which the pressure drops caused by the reverse steps reduce the hydrodynamic film force, while they scarcely affect the film stiffness if the step recesses are deep enough. Thus, the clearance is controlled at high-speed operation. The numerical analysis clarifies that the leakage flow rate of the seal is less than a critical value over the entire range of rotating velocities. The critical leakage flow rate which corresponds to a zero hydrodynamic film force condition is determined by the seal face design, and it is independent of the balance ratio. If the seal operates at a relatively low balance ratio, a hydrodynamic lubricating film is formed at a low velocity. In addition, leakage is limited at a high velocity. The experimental results confirm that a seal with reverse steps shows excellent performance over a wide range of rotating velocities.