Fluidic sealing effect on flow structure in labyrinth shroud with slotted fins

The paper analyses the flow structure of the recently introduced fluidic sealing technique that can limit the leakage flow through the labyrinth seal. The main idea behind the concept is to introduce a high-velocity jet into the gap. The jet is introduced through the slot in the fin of the seal, connecting the upstream surface of the fin with the gap. The jet is driven by the naturally occurring pressure difference, thus the solution is passive. The concept was verified using test section measurements and numerical simulations, proving effectiveness. However, the physical phenomenon standing behind the effectiveness was not studied thoroughly. A deep analysis of the flow structure in the labyrinth seal with fluidic sealing was performed based on RANS results. In addition, LES simulations were performed to allow for even more insight into the flow. The analysis revealed that the fluidic sealing introduces much non-uniformity into the flow, in comparison to the reference configuration, causing intensive mixing. The energy spectrum reveals that increased mixing raises the levels of high-frequency kinetic energy oscillations, which additionally promotes dissipation.