Blade solidity
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 s = 2 π r m / n b {\displaystyle s=2\pi r_{m}/n_{b}} is the spacing r m {\displaystyle r_{m}} is the mean radius n b {\displaystyle n_{b}} is blade number Chord length c is the length of the chord line In case of an axial flow impeller, the mean radius is defined in terms of hub ( r h {\displaystyle r_{h}} ,inner radius) and tip radius ( r t {\displaystyle r_{t}} ,outer radius) as : r m = [ ( r t 2 + r h 2 ) / 2 ] 0.5 {\displaystyle r_{m}=[(r_{t}^{2}+r_{h}^{2})/2]^{0.5}} Blade solidity affects various turbomachinery parameters, so to vary those parameters, one needs to vary blade solidity.