Design of Rim Driven Waterjet Pump for Small Rescue Vessel
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Naval architecture and ocean engineering (MPNAV), MSc
Publicerad
2014
Författare
Andersen, Thor Peter
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The hydrodynamic design and performance analysis of a pump with an electromagnetic rim driven impeller and with an open centerline is performed. The pump is the driving force of a waterjet system for a small rescue vessel. The rim-engine driving the pump is already developed and generates dimensional constraints for the pump design. The purpose of the open centerline is to avoid entanglement, and thereby downtime, if ropes are sucked into the system. The rescue boat is used to tow multiple life rafts and a high bollard pull force of 4 kN is therefore required, a top speed of approximately 20 knots is desired. The design work have been carrier out using TurboDesign1 and the performance is analysed using computational uid dynamics, specifically Menters SST k - w turbulent flow model in Ansys Fluent. Three pump congurations are analysed and compared in order to study the effect of the open centerline and if a pump design without guide vanes is feasible. The performance analysis shows that a pump without guide vanes is unable to provide the required thrust and thereby not feasible. The thesis concludes that the final concept design for the rim driven hubless pump is able to deliver the force needed to reach a top speed of 25 knots. The required force for the bollard pull condition is, however, not achieved due to cavitation in the pump. A maximum efficiency of approximately 70% is reached. This is an acceptable efficiency, but it is low compared to similar standard waterjet pumps. The low efficiency reduces the cavitation properties of the pump, compared to regular pumps with similar dimensions, as the loading of the blades must be higher to achieve a force production similar to a standard pump. A goal of the future work should be to improve the cavitation properties of the system. There are several ways to improve the cavitation properties, however, the most efficient measure is a redesign of the inlet duct and an increased impeller diameter, meaning a redesign of the electromagnetic engine driving the pump.
Beskrivning
Ämne/nyckelord
Farkostteknik , Vehicle Engineering