Automatic shape optimization of the first step labyrinth seal of a geothermal steam turbine

Introduction. The design of straight labyrinth seals for a steam turbine has had little progress concerning their geometry. As an auxiliary system, its current shape causes a significant loss of efficiency in this machine. Objective. This study aims to evaluate the use of an automatic optimization process to define a more suitable seal profile that increases the pressure ratio at the first stage of a steam turbine installed in a geothermal field in México. Materials and Methods. Multidisciplinary software, controlled by a PowerShell script, were coupled to optimize the seal shape in response to the flow and pressure field given by a computationally cheap CFD model of the first step of the labyrinth seal. Results and Discussion. By parameterizing the seal geometry, the leading edge was automatically manipulated with the numerical algorithm, obtaining an angle tendency towards 45°. This new leading edge decreased the outlet pressure of the seal system by 1.2%, which, for a total of 5 stages in the turbine with the same seals, would result in a 6% pressure reduction. Conclusions. It is inferred that this practical methodology could easily update the seal design during the turbine re-powering operations.