External torque
extracted from the fluid: Tz =
ρ Q [( r2 Vt2
˗ r1 Vt1 ]
where ρ Q
is the mass flow rate crossing the control surface (It is the same
entering and leaving the
control surface). ρ Q = dm/dt
r2 Vt2 where
r2 is the radial distance to the exit on the vane and Vt2
is the tangential
component of the
absolute fluid velocity of the fluid particle at the exit
r1 Vt1 where
r1 is the radial distance to the entrance on the vane and
Vt1 is the tangential
component of the
absolute fluid velocity of the fluid particle at the entrance
Tz is the external torque driving the
impeller in ft lb or in
N m
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