Brochure

r
1
r
2
α
1
α
2
U
1
U
2
C
1m
C
2m
C
2U
C
2
W
1
W
2
β
1
β
2
ω
W
2
W
1
W
1
C
1
C
1U
C
2
C
2U
C
2m
C
1m
C
1m
U
2
U
1
U
1
β
1
α
1
β
2
α
2
W
2
W
1
W
1
C
1
C
1U
C
2
C
2U
C
2m
C
1m
C
1m
U
2
U
1
U
1
β
1
α
1
β
2
α
2
61
61
The second plane is defined by the meridional velocity and the tangential
velocity.
An example of velocity triangles is shown in figure 4.2. Here U describes the
impeller’s tangential velocity while the absolute velocity C is the fluid’s velocity
compared to the surroundings. The relative velocity W is the fluid velocity com-
pared to the rotating impeller. The angles α and β describe the fluid’s relative
and absolute flow angles respectively compared to the tangential direction.
Velocity triangles can be illustrated in two dierent ways and both ways are
shown in figure 4.2a and b. As seen from the figure the same vectors are re-
peated. Figure 4.2a shows the vectors compared to the blade, whereas figure
4.2b shows the vectors forming a triangle.
By drawing the velocity triangles at inlet and outlet, the performance curves
of the pump can be calculated by means of Euler’s pump equation which
will be described in section 4.2.
1
2
Figure 4.2a: Velocity triangles
positioned at the impeller inlet
and outlet.
2
1
Figure 4.2b: Velocity triangles