Blade solidity
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Blade solidity is an important design parameter for the axial flow impeller and is defined as the ratio of blade chord length to spacing.
- Blade Solidity = c/s
Where
- is the spacing
- is the mean radius
- is blade number
- Chord length c is the length of the chord line
In case of an axial flow impeller mean radius is defined in terms of hub (,inner radius) and tip radius (,outer radius) as :
Blade solidity affects various turbomachinery parameters. So to vary those parameters one needs to vary blade solidity but there are some limitations imposed by Aspect ratio (wing) (span/chord), pitch. If an impeller has few blades i.e high pitch it will result in less lift force and in a similar manner for more blades i.e. very low pitch, there will be high drag force.
Blade solidity should not be confused with rotor solidity, which is the ratio of the total area of the rotor blades to the swept area of the rotor.