Highly efficient turbomachinery requires high performance sealing systems to minimize varnish between rotating and stationary parts. A conventional sealing system such as a labyrinth seal requires a certain gap between the seal and the rotating counterpart to prevent rubbing and structural damage. The gap can therefore not be arbitrarily small, which limits the reduction of leakage. New sealing technologies, such as brush seals, offer great potential for reducing leakage. They essentially consist of a flexible bristle pack arranged between a support ring and a cover ring. Their greatest advantage over other sealing concepts is the very small gap between the bristle pack and the rotor and thus a reduced leakage mass flow. This small gap can be achieved due to the high radial flexibility of the bristles without the risk of structural damage due to rubbing. In addition to reduced leakage, brush seals offer further advantages such as lower weight, reduced axial space requirements and improved rotordynamic properties.

Objectives of brush seal research:

In gas turbines, rubbing between brush seals and the rotor can occur for various reasons, such as mechanical rotor expansion, uneven thermal expansion and sudden changes in operating conditions. Thanks to the flexible structure of the brush seal, the contact forces during a rubbing event are reduced; however, the frictional heat input can still be considerable. This heat input can lead to a detrimental additional thermal load on already highly loaded rotor systems. Therefore, an understanding of heat input and heat transfer to the rotor and brush seal is necessary for the reliable use of brush seals.

Therefore, the research objectives are

1. To quantify the heat input due to brush seal brushing and assess the seal performance using experiments and FE analysis;
2. to develop a new model to predict the heat input;
3. understanding the physical mechanisms.