Correlation of Deterministic Flow Phenomena in Labyrinth Seals

• Applicant: Dr.-Ing. Lars Wein
• Subject Area: Hydraulic and Turbo Engines and Piston Engines
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545690683

Preliminary Large Eddy Simulations of a labyrinth seal made by the applicant, proved the presence of deterministic flow phenomena. More specifically, time a varying periodic vortex shedding at the tip of the fins and turbulent flow structures in the boundary layer of the rotating inner cylinder have been identified, referred to as turbulent streaks. The vortex sheading causes aero acoustic emissions and mechanical vibrations. In case of aero acoustic resonance, complete failure and damage of turbomachines can occur. The turbulent streaks determine the energy producing range in the turbulent spectra and, therefore, the spatial resolution of the computational model. A wrong computation of these streaks caused by too narrow computational domains or too coarse grids end up into too small circumferential velocities of the flow. This the mixing losses between core flow and leakage flow of a turbomachine strongly depend on the velocity triangle of both flows, a wrong prediction of circumferential velocities leads to a wrong prediction of mixing losses. Reducing the complexity of the problem to a Taylor-Couette flow shows, that even some industrially relevant models based on the Reynolds-Averaged Navier-Stokes equations struggle correctly predicting the drag of the rotating cylinder on the flow. Therefore, new models and deeper understating of these deterministic flow phenomena is required. It is the aim of this project to improve the understanding of these deterministic flow phenomena and to forecast their size and frequency be correlations. To develop these correlations, Large Eddy Simulations of test cases with reduced complexity will be simulated, using a numerical method of higher order of accuracy. This includes a Taylor-Couette flow, a generic vortex chamber and a generic outlet cavity. The geometric and aerodynamic boundary conditions determining the size and frequency of the deterministic flow phenomena will be identified and correlated by extensive parameter studies.

• DFG Programme: Research Grants