Next: Characteristic Up: Fluid Section Types: Gases Previous: Preswirl Nozzle Contents

### Straight and Stepped Labyrinth

A labyrinth is used to prevent the gas from leaking through the space between a rotating and a static device and thus reducing the efficiency. The leaking air is trapped in the successive stages of a labyrinth. It can be straight (Figure 46) or stepped (Figure 47). A stepped labyrinth is used if the gas is compressed or expanded, leading to a decreasing and increasing diameter of the rotating deviced, respectively. In a stepped labyrinth the static device is usually covered by a honeycomb structure.

Figure 46: Geometry of straight labyrinth

Figure 47: Geometry of stepped labyrinth

The formula governing the flow through a labyrinth has been derived in [14] and for the discharge coefficients use was made of [33], [29], [11] and [56]. A labyrinth is described by the following parameters (to be specified in that order on the line beneath the *FLUID SECTION, TYPE=LABYRINTH card):

- t: distance between two spikes
- s: gap between the top of the spike and the stator
- D: Diameter of the top of the spike
- n: number of spikes
- b: width of the top of the spike
- h: height of the spike measured from the bottom of the chamber
- L: width of a honeycomb cell
- r: edge radius of a spike
- X: distance between the spike and the next step
- Hst: height of the step

Please look at the figures for the meaning of these parameters. Depending on the kind of labyrinth, not all parameters may be necessary.

Next: Characteristic Up: Fluid Section Types: Gases Previous: Preswirl Nozzle Contents