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Volute Design

Volutes are typical casings for radial machines. Their accurate design is essential to the operation and overall efficiency of the machine.


  • Definition of the inlet cross-section Single or double spiral, considering flow conditions of the neighboring component
  • Various cross-sections Symmetrical or asymmetrical cross-section shapes whose definition may vary in the circumferential direction
  • Spiral design according to common design theories Choose between alternative design laws or your own geometric progressions
  • Discharge diffuser Tangential or radial outflow direction
  • Spiral tongue Choose between different geometric shapes

Design steps for volutes

Applicable to pumps, fans, compressors and turbines

1. Volute inlet

  • Definition of inlet width and inlet diameter 
  • Positioning relative to adjacent components
  • Single or double spiral

2. Cross-sections

  • Rectangle, trapezoid, circle
  • Radius-based
  • Free-form geometry, Bezier
  • Symmetrical and asymmetrical
  • Modify cross-sections in circumferential direction
  • External and internal volutes

3. Spiral geometry

  • Design laws according to Pfleiderer or Stepanoff
  • Option to define own area / radius relation
  • Define spiral wrap angle and start angle
  • Option to correct cutwater
  • Option to correct scaling

4. Discharge diffuser

  • Tangential or radial outflow direction
  • Free-form geometry
  • Round or rectangular end section
  • Diffuser length, cone angle
  • Option to twist outlet in axial direction
  • Option to modify cross-section area distribution

5. Cutwater, tongue

  • Simple, fillet or sharp mode
  • Various geometry parameters

Volute design made easy

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