Radial element blade
Radial element blades are used especially with highly loaded fast speed turbines in order to avoid bending stresses within the blades due to centrifugal forces. The blades are composed of radial blade fibres if straight lines can be put into the mean surfaces in a way that they go through the axis of rotation at z = constant.
Radial element blades require the following geometrical boundary conditions for radial & mixed-flow impellers:
•Blade angle at input (turbines) or output resp. (all other types): β ≈ 90°
•Inclination angle from hub and shroud to the horizontal: ε' < 90°
•Vertical trailing (turbines) or leading edge resp. (all other types) with z ≈ const.
•Small wrap angle: φ ≈ 360°/number of blades