Leakage Characteristics of Stepped Labyrinth Seals : A Continued Report. Effects of Shape Factors on Leakage rate

Abstract

In this study, the effects on the leakage rate shape factors, such as relative position a_D/l, number of fin n, height of step h₂, depth of groove h₁ and pitch l, thickness δ and clearance of fin ε are investigated in detail for stepped Labyrinth seals (downward stepped type), which have a higher efficiency from the practical viewpoint, and their optimum shapes at both the stationary and rotating states are determined. The geometrical values for its optimum shape are in those cases when h₂/l, a_D/l, h₁/l, δ/l, and l/ε take the values around 0.2, 0.4∼0.5, 0.5∼0.6, 0.4 and 15, respectively. On the bases of these results a method of predicting the leakage rate, and the plan procedure are described. On the other hand, the present experimental results is obtained by using a comparatively larger rotor to increase the peripheral velocity. It is shown clearly from both equations of continuation and motion represented nondimensionally that their results can be applied even if the clearance of fin is small in comparison with the axial diameter, such as in the case of practical machines.