Optimization And Design Research On Marine Pre-swirl Stator-propeller By CFD

As the global energy crisis intensifies,resulting in higher and higher operating costs of ships,reducing operating costs has become one of the major topics in the shipbuilding industry.The study of ship energy conservation technology began in the 1970 s,and these technologies are summarized in two ways: new hull form with excellent hydrodynamic performance and additional energy-saving devices.The pre-swirl statorpropeller studied in this paper belongs to the latter.Its basic working principle of pre-swirl stator is to pre-spin the inflow of propeller,reduce the circumferential induced velocity of the trailing wake,recover the rotational energy in the wake of the propeller,and help to improve the inflow of the propeller and hull-propeller matching in order to achieve a certain energy-saving effect.In this thesis,a numerical method based on lifting-surface method and RANS equations is applied to predict the energy-saving efficiency of preswirl stator-propeller and to simulate the viscous flow around ship hulls in three different systems: i.e.,the propeller in open water,the towing resistance experiment and the self-propulsion test.The sliding mesh technique is used to simulate the rotating propeller and the turbulence is modeled by RNG k-ε and SST k-ω model,and then the pressure distribution and flow field on the hull surface and its appendages are analyzed.By comparing the self-propulsion factors,the energy-saving mechanism of pre-swirl stators is analyzed and verified.Then,the pre-swirl stators are optimally designed by using the theory of lifting-surface based on the research of ship numerical simulation.Various stator was derived by changing blade’s deflection angle and the self-propulsion factors with each stator were calculated.The circulations of stator and propeller were evaluated quantitatively based on the lifting-surface method.The tendencies of hull efficiency,relative rotational efficiency and propulsive efficiency changing with the circulation ration of stator to propeller were analyzed.By comparing the propulsive efficiencies the optimum circulation ratio can be found,and the result may provide some advantageous guide for optimum stator design.Finally,The conclusion was verified by a chemical propeller and its matching propeller,which proves the applicability of this optimization principle.The numerical method applied in this thesis can reasonably simulate the hydrodynamic performance of ship and its appendages to study the energy-saving effect of pre-swirl stators.The conclusions have reference values for the theoretical design of pre-swirl stators.