Measurements and Modeling of the Movement Behavior of a Radial Adaptive Seal

The radical change in the energy market with a raising share of renewable energy pro-
duction leads to new operating cycles in turbo machinery. The machines must be opti-
mized for frequent transient load cycles and part load utilization. New radial adaptive
sealing concepts in the secondary air system can help to increase part load efficiency and
achieve a long service life. These seals are pressure-activated and adapt their gap width
during operation. The sealing concepts have to be analyzed in more detail to fully under-
stand their operational behavior. In this paper, a model to understand and predict the
movement of a radial adaptive seal called hydrostatic advanced low leakage (HALO)
seal is presented. Experimental results of the gap width, leakage, and pressure distribu-
tion are used in combination with two-dimensional (2D) computational fluid dynamics
(CFD) to obtain force distributions across the seal for static operation. These data are
used to derive a model to predict the forces acting on the seal as well as the operational
gap width, which is necessary for a reliable seal design.