Measurement and Evaluation of Swirl-Type Flow in Labyrinth Seals of Conventional Turbine Stages,
TECHNISCHE UNIV MUNICH (GERMANY F R) INST FUER THERMISCHE KRAFTANLAGEN
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Previous studies of rotor whirl instability pointed out two different mechanisms inducing lateral forces within non-contacting labyrinth-type seals. Evaluating the part of exciting forces that results from leakage losses is possible by means of variable flow contraction in the gap of a seal with variable clearance at the circumference. The dominating part of exciting forces has its origin in unequal pressure distributions at the circumference of the seal with a shaft in out-of-centre position. The pressure distribution is mainly influenced by swirl-type flow at seal entry.