Trans RINA, Vol 153, Part A1, Intl J Maritime Eng, Jan-Mar 2011
J=0.2-Hull J=0.6-Hull J=1-Hull J=1-Open J=0.6-Open J=0.2-Open
4.5 5
3.5 4
2.5 3
1.5 2
0.5 1
0
-40 -30 -20 -10 0 10 20 30 40 Heading angle
Figure 29: Radial bearing loads in different oblique inflows as a portion of the propeller weight on bearing A (Pulling mode)
5. CONCLUSIONS
It is found that the hydrodynamic side force and bending moment are quite large in both oblique inflow and in waves – significantly larger than the design values suggested by ITTC. Larger side forces and bending moments are found at high azimuth angles in calm sea than in waves (propeller azimuth angle was fixed at zero in waves), although extreme wave conditions were not tested.
Regarding the ship hull wake influence on the propeller loads in different azimuth angles, it is found that the hull wake has a strong effect on the propeller performance and shaft outwards
bending loads when from the ship
propeller is turned hull centreline. Then the
0 1 2 3 4 5 6
0 0.2 0.4 0.6 0.8 Advance coefficient
Figure 30: Amplitude of radial bearing loads in waves as a portion of the propeller weight on bearing C (Pulling mode)
propeller experiences much lower loads in the vicinity of the hull wake compared to the open water condition - while only a small difference is seen in forces and moments between inward heading angles in the behind and open water conditions. The maximum side forces and bending moments experienced in calm water behind the hull are of the same order of magnitude as in open water. However,
different hull different results in this respect.
HS-2S-225mm HS-2S-170mm HS-2S-160mm FS-2S-160 mm FS-2S-200 mm
1 1.2
The side force and bending moment in waves are considerably larger than in calm water at zero azimuth angle. The propeller experiences larger bending loads in the head sea than in following sea condition (It is also a limited number of wave cases that has been tested (wave period was kept constant).
Finally, hydrodynamic side forces and bending moments are important for both steerable thrusters and shafted propeller systems, and should be considered in the design of propulsion drive train and its mechanical components. Even though a shafted propeller system operates less in highly oblique flow compared to an azimuth propulsor, the propeller will experience significant side forces and bending moments in waves.
3.5 4
2.5 3
1.5 2
0.5 1
0 0 6. ACKNOWLEDGEMENTS
This research is sponsored by The Research Council of Norway through the research project SeaPro at The University Technology Centre of Rolls Royce at NTNU.
HS-2S-225mm HS-2s-170mm HS-2S-160 mm FS-2S-160 mm FS-2S-200 mm
0.2 0.4 0.6 0.8 Advance coefficient
Figure 31: Amplitude of radial bearing loads in waves as a portion of the propeller weight on bearing A (Pulling mode)
2. 1 1.2
7. 1.
REFERENCES Carlton, J.S., “Marine propeller and
propulsion’’, Butterworth Heinemann, Oxford, second edition 2007
Amini, H., Steen, S., Spence, S.J. “Shaft side force and bending moment on steerable thrusters in
off-design condition’’.11th international symposium on practical design of ships and A-20 ©2011: The Royal Institution of Naval Architects shapes might give
Fr*/Propeller weight at A Fr*/Propeller weight at C
Fr*/ Propeller weight at A
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