Abstract

A modification of a conventional straight tooth labyrinth seal with variable tooth height is proposed. The baseline and modified labyrinth seal teeth with solid land are examined by three-dimensional CFD numerical modeling of the flow field and evaluated for predicting the leakage through the seal during the engine operation. Stocker’s [1] static labyrinth seal experimental data is used to validate the CFD methodology used in this paper. The baseline and the proposed modified design [2] — “Labyrinth seal with variable tooth heights” are numerically studied with solid lands and evaluated to measure the reduction in leakages. The objective of this study is to provide an improved sealing effectiveness by restricting the leakage flow and controlling the seal leakage during the operation of the engine. In this study, a conventional straight-through four-tooth labyrinth seal with solid land is used as the baseline model. It is first evaluated at different unworn constant radial gaps — between the teeth tips and solid land. In the proposed modification, the height of the intermediate teeth of the baseline four-tooth are varied. The teeth heights are designed in such a way that intermediate longer teeth form a very small or tighter radial gap at start of operation. The shorter ones are designed based on the expected wear groove/rub depth considered by the seal designer.

Results indicate that the proposed modification — Variable height teeth tips, reduce the seal leakage by over 50% compared to the baseline. The advantage of this modified design over a baseline seal is that at unworn or worn conditions, the teeth tips always forms a considerable tighter radial gap when compared with baseline seal. The achieved sealing is such that during engine operation of the seal, even if the seal gets worn, the overall leakage is significantly reduced.

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