The PBT is a generic impeller design. It is a 4bladed turbine with 45o pitched
blades. Blade width is 0.2 times its swept diameter. The PBT has long been considered an
axial flow impeller. That really depends on its D/T. For small D/T, the PBT is an axial
flow impeller. For very large D/T, the PBT is almost a radial flow impeller. A 3bladed
PBT with 30o pitched blades is almost as axial as a hydrofoil. In Europe, the 6bladed
version of the PBT is more common.
Np=1.27, Flow Number Nq=0.79
