Study On The Scale Effect Of Energy Conservation Of Ship Energy-Saving Devices

Improving the efficiency of energy conversion is a rigid demand for today's transportation industry.In this respect,the ship propeller plays a very important role in marine transportation because it is the key unit to determine the overall propulsion efficiency of the ship.Promoting propulsion efficiency is a good way to reduce fuel consumption and CO2 emissions.In the method of improving the propulsion efficiency of ships,ships with the additional hydrodynamic energy saving device is widely accepted by the ship-owners,because it has advantages of convenient installation,no influence on general arrangement,good efficiency of energy saving,fast recovery cost and so on.However,there is not a very good extrapolation method to the scale effect of the tank model test,so its real energy saving effect is also suspected by the ship-owners.This paper studied the ship resistance and performance of two typical energy saving devices(Pre-Swirl Stator and Thrust Fin),used the completely-similar theory to obtain the real energy saving effect of the energy saving device under the full scale ship Reynolds number,and used the test method and numerical simulation to analyze the powing performance of 3 different scale ship models with energy saving devices,used the different extrapolation methods to analyze the scale effect of energy saving devices,as well as compared the predicted results of various extrapolation methods.The main work of this article is as follows:Introduced the experimental model,the test condition,the experiment process and the test equipment.Simply described the theoretical method used for numerical calculation and the calculation model.Analyzed and calculated the drag,propeller thrust and torque,the output waveform and flow field diagram to verify the general numerical calculation model adopted in this paper.Obtained the numerical extrapolation method(Complete-Similarity Theory Simulation)adopted in this paper by deriving the similarity theory of the self propulsion experiment.Introduced two common extrapolation methods of ship resistance and performance,and the MARIC method.At the same time,obtained the extrapolation method used in this paper by analyzing the assumption of the ITTC1978 method and the physical parameters involved in the scale effect.It has no scale effect when enabling the model and the real ship have the same Reynolds number by changing the kinematical viscosity coefficient of the fluid.Verified the numerical calculation of Reynolds number in detail.And analyzed the detailed parameters of resistance and flow field at different scales to prove that the numerical calculation of Reynolds number is applicable to model resistance and self-propulsion test simulation.Then,used the real ship Reynolds number simulation to conduct the resistance and self-propulsion simulation of the naked hull and ship with Pre-Swirl Stator and rudder with additional thrust fin.Analyzed the energy saving mechanism of these energy saving devices by flow field and other physical quantities,and obtained the real energy saving effect of the energy saving device: the Pre-Swirl Stator is about 5.45%,and the thrust fin is 1.81% approximately.Carried out 3 different scale model tests,including resistance test,propeller open water test and self-propulsion test.At the same time,the ship's hydrodynamic energy saving devices were installed on these test hull models: Pre-Swirl Stator and Thrust Fin.Conducted the fine flow field measurement test to obtain the fine flow field of the hull and propeller with and without energy saving devices to analyze the energy saving mechanism of ESDs.At the same time,analyzed the causes of scale effect through experimental results,and adopted 3 different extrapolation methods to extrapolate the results which show that the proposed extrapolation conversion method can effectively reduce the scale effect.Introduced the prediction method of ship resistance and performance in wave condition,and carried out ship resistance and performance test with energy saving devices in 3 different scale waves to analyze the energy saving effect of Pre-Swirl Stator and Thrust Fin in waves respectively.What's more,conducted the ship resistance and performance test of ship with energy saving device in still water and waves to analyze the energy saving mechanism and energy saving effect of combined energy saving devices in still water.And tried to apply the method proposed in this paper to the ship resistance and performance prediction with energy saving devices in waves.The results show that the method proposed in this paper can reduce the scale effect of the ship resistance and performance prediction with energy saving devices in a certain degree.