Labyrinth seals design using topology optimization based on a level set approach

Abstract

This work is part of the project from Brazilian Center of Research (CEPID) for Innovation in Gas, Fapesp number: 2014/50279-4. It aims to optimize the performance of labyrinth seals, which are non-contacting seals (or clearance seals) used extensively in turbomachinery. There are in the literature several experimental and numerical studies devoted to choosing, through flow control, what designs of labyrinth seals perform better. These studies are important not only for efficiency issues but there is also the climatic factor concerning the air pollution: sources show that 60% of methane emissions are caused by leakage of pneumatic devices. The purpose of this research is to extend the design concepts of labyrinth seals (currently limited to change the geometric parameters of the classical designs that exist in the literature and industry) employing Topology Optimization (TO). Topology Optimization is a computational method that allows for the design of structures in an optimized shape in order to maximize or minimize an objective function. As the technology of energy sectors has been characterized by a tendency of equipment with increasingly higher operational pressures, a structural analysis is imposed on the problem through stress constraints. Thus, the main objective is to reduce labyrinth seal leakage with alternative designs provided by TO and validated against mechanical failure. Therefore, a methodology for TO of fluid-structure interaction problems is developed in order to minimize the fluid flow subjected to local stress constraints. The structural and fluid domains are modeled separately and interact through their interfaces, whose load location (fluid pressure) is allowed to change during the optimization procedure. A level set approach is used to represent the topology which is considered appropriate to these type of problems since it allows for a clear separation between fluid and solid regions within the background domain. (AU)