The open water characteristics for a large systematic series of Controllable Pitch Propellers (CPP) were recently measured at MARIN, including ducted propellers. Around the world people involved in ship and propeller design have been working with the open water thrust and torque characteristics of the WAGENINGEN B-series for fixed pitch propellers. However, increasingly today CPP are being used both in open configuration and in nozzles. Such CPP can operate over a wide range of speeds and they are installed on navy vessels, merchant ships, tugs and offshore supply vessels but also on offshore units with DP capabilities.
To support the design, selection and use of CPP and to enable the modeling of the thrust and torque characteristics of these propulsors in DP simulations for example, MARIN has developed a newly designed, systematic CPP and ducted CPP series. Thrust, torque and blade spindle torque in open water conditions are measured at model scale in all positive and negative inflow conditions. As each propeller with a specific design pitch can be operated over a range of operational pitch, an extensive test program has to be conducted.
Quasi-steady Technique
To enable an efficient measurement procedure, a new so- called quasi-steady open water test technique has been developed and verified. With this new method forward speed and rpm are varied over the measurement run and in this way the complete open water characteristics in all quadrants are derived from a limited number of runs. MARIN's numerical milling machine is used to build alloy models because lightweight propeller models are required when using this approach. To measure the blade spindle torque a dedicated test hub is used where one of the blades is fitted to a torque sensor. The research work is carried out in a Joint Industry Project so that the actual series could be selected and designed following input from several leading propeller designers and manufacturers and the costs and results can be shared. So far, 22 companies are participating and this has led to the extension of the series to 31 propellers in 46 configurations. Each propeller with a specific design pitch is then tested over the complete range of operational pitch settings.
Measurements have been conducted in MARIN's Deepwater Basin and two series have already been completed and the analysed data delivered to participants.
Jie Dang is senior project manager at the Ships department of MARIN, the Maritime Research Institute Netherlands. MARIN offers simulation, model testing, full-scale measurements and training programmes, to the shipbuilding and offshore industry and governments. j.dang@marin.nl
(As published in the December 2012 edition of Maritime Reporter - www.marinelink.com)
