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<< Click to Display Table of Contents >> Cross Section |
  
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<< Click to Display Table of Contents >> Cross Section |
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► VOLUTE | Cross Section 
The shape of the volute cross-sections can be selected here. The general cross section shape is illustrated whereas the radial extension is assumed.
The sections will be scaled later in the Spiral development areas design step according to the selected design rule and the required height h.
In general, very small cross-sections width should be avoided. The achievable cross-section shape strongly depends on manufacturing and the available space.
The table contains the cross section definitions (at least 1 cross section). Each cross section is defined by:
•the circumferential position: angle φ
•(de)activation by selecting the checkbox on the left side (at least 1 cross section has to be active)
•cross section type on the left side
•optional cross section type on the right side or symmetric
The section definition is running in the range 0° < φ ≤ 360°. The section at φ=0° is flat always - therefore a section definition at this position makes no sense.
Between 2 neighboring cross section definitions a smooth transition is realized. If only a single section is defined then this definition is used for all circumferential positions.
The following cross section types are available:
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Rectangular most simple cross-section shape; cannot be achieved in cast parts; only sensible for low specific speeds, since otherwise the cross-section becomes too large |
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Trapezoid cannot be achieved in cast parts; the angle δ can be specified; results in a flatter cross-section than a rectangular cross-section, with less intense secondary flow |
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Round - symmetric simple elliptic geometry with a beneficial stress distribution; does not develop on rotation surfaces •Ratio of ellipse radii: axis ratio is preserved for developing sections. (ratio of one gives a circular section) |
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Round - asymmetric, external more favorable secondary flow structure than with a symmetrical cross-section; often with mixed-flow impellers •Ratio of ellipse radii: axis ratio is preserved for developing sections. (ratio of one gives a circular section) •Strictly external: cross sections don't fall below inlet radius •Open to right: asymmetric development to right (pos. z-direction) •Square on top: square shape on right top of cross section |
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Round - asymmetric, internal limitation of radial extension; ratio of ellipse radii possible; additional bend necessary |
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Bezier - Rectangle type analogous with Rectangle; with chamfers (cast radii) |
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Bezier - Trapezoid type analogous with Trapezoid; with chamfers (cast radii) |
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Line segments |
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Radius based |
Here you can specify some properties of the currently selected cross section in the table Sections.
Details can be found in the table above and in the specific topics.
Except the Radius based and round section types, each section definition can have a specification of the draft angle λ. Currently, left and right side of the cross sections do not form an edge at the center line due to problems of cutwater design. |
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For double volutes the cone angle (opening) of all cross sections has to be constant. Therefore, round types and Line segments are not available.
If any of these impossible cross section types are already part of the project then they are converted automatically when selecting the double volute type (see Setup & Inlet). The following message will be displayed:
•"Volute section type(s) were modified due to double volute requirements."
if any cross section type was modified automatically
•"Cone angle(s) were modified due to double volute requirements."
if the cone angle of any cross section was adapted automatically
