3.2 Idealised Mean Line Analysis of a Radial Fan
105
3.2.4 Performance Characteristics with Idealised Flow
A first characteristic represents the total pressure rise in the fan as a function of the
flow rate. Their relation follows from Euler’s equation. Without pre-swirl it applies
that
(3.6)
0,
2 2
2 2
2
2
2
2
2
2 2
(
)
.
t
u
r
p
Q
u v
u u v tg
u u
tg
d b
D
b
b
r
p
∞
=
=
+
=
+
Fig. 3.6 Variation of the degree of reaction and of pressure coefficients with blade angle at the
rotor outlet (β 2 ); the radial velocity is drawn exaggerated for clarity
Fig. 3.7 Forward curved (F), radial end (R) and backward curved (B) blades
105
3.2.4 Performance Characteristics with Idealised Flow
A first characteristic represents the total pressure rise in the fan as a function of the
flow rate. Their relation follows from Euler’s equation. Without pre-swirl it applies
that
(3.6)
0,
2 2
2 2
2
2
2
2
2
2 2
(
)
.
t
u
r
p
Q
u v
u u v tg
u u
tg
d b
D
b
b
r
p
∞
=
=
+
=
+
Fig. 3.6 Variation of the degree of reaction and of pressure coefficients with blade angle at the
rotor outlet (β 2 ); the radial velocity is drawn exaggerated for clarity
Fig. 3.7 Forward curved (F), radial end (R) and backward curved (B) blades