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Blade angles |
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Blade angles |
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Ü Impeller | Blade properties 
On this tabsheet the blade angles are calculated.
The mean lines depend on the number and the meridional position of profile sections as well as the blade angles. Blade angles βB1 and βB2 are calculated from the velocity triangles, whereby the blade blockage of the flow channel and the slip velocity is considered.
The degree of freedom when designing the blades depends on the selected blade shape. Referring to the blade angles this means, that they are marked as (auto) and are result of the Mean line calculation.
Panel Blade angle βB:
| ▪ | Specifying number of blade profile sections for further blade design using the vertical track bar |
| ▪ | Calculation of blade angles using values from Blade setup by pressing button Calculate βB |
| ▪ | Manual adaptation of calculated blade angles if required |
Calculation or input of blade angles can be executed for 2 up to 11 blade profiles. Further blade design is realized according to the defined blade profile number.
When using 2D blade shapes a low number of profiles may be sufficient in dependence of the leading edge shape, e.g. for a straight leading edge. For that reason the initial design for ventilators is made by 2 blade profiles.
For Radial element blades the number of blade profiles is fixed to 11. Beyond it a Distribution exponent is discernable. This exponent has influence on the distribution of the blade profiles and herewith especially on the shape of the leading edge (turbine). For highly spatial curved blades the continuity of the blade surface can be influenced by this parameter.
Distribution exponent |
Impact |
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Value 1: blade profiles uniformly distributed (default) |
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Value<1: blade profiles concentrated towards shroud |
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Value>1: blade profiles concentrated towards hub |
With ruled surface blades the number of blade profiles is limited to 2.
Blade angles are computed under consideration of the equations listed below. They remain unchanged by default if they are determined once. If main dimensions or meridional contours are modified or, on the other hand, values of blade thickness or slip velocity are renewed, a recalculation of blade angles should be executed by pressing the button Calculate βB. This recalculation is made automatically if the checkbox Automatic is selected.
¢ Details of calculation of Inlet triangle
¢ Details of calculation of Outlet triangle
The blade angles are calculated for hub and shroud. On panel Distribution from hub to shroud you can define how the blade angles of the inner sections are defined.
When using splitter blades you can select if the splitter blades is a truncated main blade (Splitter blade linked to Main blade). Otherwise the splitter blade can be designed completely independent.
All meridional lines which will be used for blade design are displayed in the diagram. The number of lines can be adjusted with the track bar on panel Blade angle βB.
Page url: http://www.cfturbo.com/fileadmin/content/manual/en/index.html?bl_angles.html
