Experimental investigation of the effect of waves and ventilation in depressurised conditions

AuthorsGerco Hagesteijn and Joris Brouwer
Conference/JournalThird International Symposium of Marine Propulsors (SMP), Launceston, Tasmania
DateMay 15, 2013
Experimental investigation of the effect of waves and ventilation in depressurised conditions on a pod-propeller of a cruise liner model
When ventilation occurs unpredictably and uncontrolled, the propeller starts racing due to the reducing torque in the ventilated regime. This might cause severe damage to traditional Diesel engines with at the same time imposing heavy efficiency losses as at the higher RPM of a racing propeller; the advance coefficient of the propeller is shifted into the unfavourable off-design regime. One of the claimed advantages of electric Podded propulsion is that the electrical engines can cope better with thedropping of torque, resulting in less engine damages . On the other hand the loading of the propeller bearings is more difficult to dimension due to the poor knowledge available, in the public domain, on Podded propulsors in service or more specific, seakeeping conditions. During higher sea states the propeller loading fluctuates due to the variation in speed and the vertical motions of the vessel, which will result in different cavitationbehaviour and inception speeds compared to the calm water conditions. Moreover, bas ed on past experiments in MARIN's Seakeeping Basin, it was seen that ventilation can sometimes occur on pods as well, a phenomenon which was observed to greatly affect blade forces and moments, and thus the shaft loading as well.
Tags
sustainable propulsionwaves, impacts and hydrostructuralresistance and propulsionmarine systemspropellerpropulsorwaves