US Patent 8002286 Aerodynamically mistuned labyrinth seal

A labyrinth seal having two or more knife edges in which at least one of the knife edges has a varying radial height in the circumferential direction or a cavity formed between adjacent knife edges has a varying axial width so that the leakage flow across the gap will vary around the circumference in order that excess vibrations will not develop in the knife edges and break them. The radial height of the step that forms a gap with the lab teeth varies either sinusoidal or random. An axial spacing between the step and the associated tooth can also vary either sinusoidal or random. To minimize a cavity edge-tone effect, the corners of the steps are rounded.