Vane cascade
A vane cascade consists of regularly arranged vane profiles (see Flow profile) along a straight line (plane vane cascade) or in a circle (cylindrical vane cascade).
The co-axial, cylindrical section through the axial impeller and diffuser of a propeller pump reveals the cylindrical vane cascade of the stage. If this section is projected into a plane, the result is a plane vane cascade of the stage. See Fig. 1 Vane cascade
Fig. 1: Vane cascade: Plane vane cascade
- S: Median line of vane profile
- G: Cascade front
- La: Impeller cascade
- Le: Diffuser cascade
- l: Length of vane profile
- t: Vane pitch (vane height)
- βs: Vane angle
- e: Axial vane extension (vane height)
- u: Circumferential direction
- c: Chord
Different vane cascades can be depicted as one moves from one cylindrical section to the next through the stage of the propeller pump (from radius to radius). See Fig. 2 Vane cascade
Fig. 2: Vane cascade: Stream lines of a plane vane cascade (potential flow through a diffuser)
The description of the flow across vane cascades is frequently the object of theoretical and experimental investigations on stationary, in most cases plane vane cascades, as well as axial and mixed flow turbomachinery (Fluid mechanics). Such investigations involve two main challenges.
Main tasks of flow description
- Establishing associated flow conditions for a given vane cascade (direct problem).
- Establishing the associated vane cascade for given flow conditions (inverse problem).
While experimental findings are frequently relied on in practice, numerical flow simulation or computational fluid dynamics methods (CFD) have increasingly been applied in recent years.
