Scaling Effects on Leakage Losses in Labyrinth Seals

The accurate prediction of leakage losses through labyrinth seals in gas turbine engines depends largely on exact measurements. As tolerance effects are important, scaled-up models are used for experimental analysis. Application to real size engine conditions is of predominant importance. Measurements in a newly developed test section over wide pressure ranges with geometrically similar straight-through seal models of different scale indicate that the flow coefficient is not independent of scale. In a first attempt to clarify these questions, the results obtained from various models were correlated using Fanno-line analysis with dimensionless integral friction coefficients. The results obtained reveal the necessity for simultaneous consideration of Reynolds and Mach-number effects as well as relatively small geometrical deviations.