Abstract

Modern gas turbine engines operate in a temperature range dramatically exceeding the temperature limits of known materials. Therefore, advanced cooling schemes are an absolute necessity for efficient engines. However, the amount of cooling air directly affects the efficiency of the engine and should be kept as low as possible. For an optimal cooling air system design accurate and reliable correlations for various components are crucial. This is especially true for labyrinth seals, where the boundary conditions in a gas turbine environment differ strongly from the predominantly non-rotating test rigs, where the majority of discharge coefficients were defined. The analysis and discussion of the fluid mechanic effects of rotation and a circumferential velocity at the inlet (preswirl) on the discharge behavior of labyrinth seals in this paper provides further understanding and design characteristics for the leakage prediction. At first an extensive literature survey is presented, where the single effects are discussed. Results from numerical simulations provide additional details to analyze the literature data. In the second part, new experimental results based on the analysis of leakage measurements of convergent and divergent stepped labyrinth seals at variable rotational speeds and preswirl are presented and compared to correlations from the literature.