04-5
SECTION 04 - PROPULSION SYSTEM
Regular Fixed Pitch
The impeller pitch remains constant on all the
blades. The blades are straight with the same an-
gle from leading to trailing edges.
1. Leading edge
2. Trailing edge
1. Leading edge
2. Straight blade
3. Trailing edge
Progressive Pitch
The impeller pitch changes progressively on each
blade. The blades are bent
constantly or asym-
metrically
with different angles at leading and
trailing edges. The blade bending is done by using
a special fixture.
1. Leading edge
2. Constant bend
3. Trailing edge
4. Asymmetrical bend
A low pitch leading edge is important for good ac-
celeration and a higher pitch on trailing edge will
give better top speed.
Impeller Efficiency
The impeller efficiency is related to several pa-
rameters:
– hydrodynamic blade design
– incidence angle
– turbulence created at the inlet
– pre-rotation of water
– relative circulation
– eddy
– friction
– cavitation
F01J4NB
1
2
F01J4SA
1
17,7°
2
17,7°
3
F01J4TA
15°
15°
1
1
2
4
19°
19°
3
3
Summary of Contents for Bombardier
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