In the present work, an environment for the shape optimization of a labyrinth seal is described. A program for a parameterized, automated grid generation is coupled with a commercial Computational Fluid Dynamics (CFD) flow solver and an optimization algorithm. Standard optimization strategies, like gradient-based methods, mostly are trapped to local optima. Therefore, the simulated annealing method is applied. It allows the finding of global minima or maxima of arbitrary functions.The presented optimization method is used to minimize the leakage through a three-finned, stepped labyrinth seal. For the optimization, the step position and the step height are chosen to be variable. The characteristics of the flow fields of selected seal configurations are compared and discussed against the background of the leakage behavior of the seal.

An experimental investigation on the influence of stator rub-grooves on labyrinth seal leakage is presented in the present paper. In current labyrinth seal designs, abradable lands allow the rotor labyrinth teeth to rub grooves into the stator. These rub-grooves have a large influence on the seal leakage characteristic and impair the overall engine efficiency. To improve the understanding of rub-groove effects, discharge coefficients were determined using a plain non-rotating labyrinth seal model of scale 4:1 considering a wide variation of rub-groove geometries at different seal clearances. Three labyrinth seal types were covered in this investigation that are generally used in gas turbines, namely (1) straight-through labyrinth seals, (2) stepped labyrinth seals with forward facing steps and (3) stepped labyrinth seals with backward facing steps. To attain a deeper insight into the flow mechanisms, water-channel visualizations were performed. The large data set generated in this study, provides the basis to analyze and quantify the influence of rub-grooves on the seal leakage for the three labyrinth seal types listed above. Current results were in agreement with previous studies on worn labyrinth seals for several seal geometries.