What do you think about Schneekluth Duct and / or Propeller Boss Cap Fin (PBCF) as energy saving devices?
Schneekluth Duct and all similar Wake Equalizing Ducts (WED) improve propeller efficiency by providing an improved velocity distribution over the propeller disk and more axial flow, theoretically also reducing flow separation at the aft body. Efficiency improvement from WED, depend on the hull lines, prior installation and potential improvement of propeller inflow. Thus, the effect is usually higher on fully shaped vessel that operate on different speeds than the optimized range (almost standard on NB/VLCC of “quality” yards). Efiiciency improvement vary significantly ( a typical range is 0-8%). The Propeller Boss Cap Fins (PBCF) is an Energy Saving Device (ESD) that mainly recovers the energy losses at the propeller hub vortex downstream of the propeller (propeller outflow). Losses due to vortexes are estimated at maximum 4% of the total thrust and the operational gains on PBCFs are normally on the range of 0.5-1.5%. As the two devices target a different effect (improvement of inflow/reduction of losses at outflow), they can be combined effectively.
Nice input, thanks!
thanks for the info @Alexandros.Senteris!
I was wondering the improvement rates you mentioned are they based on existing literature, marketing brochures or actual measurements of a vessel performance?
@Stela.Spiraj the figures are indicative, based on literature and actual measurements. Marketing brochures are usually overestimating significantly the effect of the device.
I agree that marketing brochures usually overestimate the performance improvement