Theoretical Study On The Hydrodynamic Performance Of SSD Before Propeller

Super Stream Duct (SSD) is a new kind of energy-saving device. It is installed before thepropeller. On the one hand, it can increase the propulsive efficiency of the propeller bymaking the wake of the propeller disk more steady. On the other hand, it is energy-efficient byproviding some extra thrusts itself. So it can be defined as both economy and practicability.Currently, there has been very little research on the hydrodynamic performance of SSDdomestically and overseas. So it has been quite necessary to conduct more research on it. Inorder to get a better understanding of the hydrodynamic performance of SSD, this dissertationdevelops a CFD method to simulate the flowfields of the ship-SSD-propeller system. Toverify the validity of the CFD method, the results of the self-propulsion test，including themodel test of a self-propelled ship without SSD and with the SSD of15open angle from sideview installed40mm before the propeller, are contrasted with the results of the CFD method,simulating the very same two conditions. The contrast shows that the results of the CFDmethod match well with the test. So it can be concluded that the CFD method can be used tostudy the hydrodynamic performance of SSD.This dissertation mainly discusses two factors that may affect the hydrodynamicperformance of SSD. One is the shape parameter, and the other is the installation site. And theshape parameter mainly includes two elements: the open angle from side view, the ratio ofupper and lower horizontal distance. This dissertation mainly focuses on the change of thrustsand torque of the propeller, the resistance of the ship hull, the wake fraction, the relativerotation efficiency, the energy-saving effect, etc., when the shape parameters and installationsite change. The results of the CFD simulation show that different parameters and installationsites have different influences on the hydrodynamic performance of SSD. Among them, theinstallation site and the open angle from side view make a bigger influence.In the last part of this dissertation, the cavitation performance of the propeller with aSSD of an open angle of15from side view, installed40mm before it, and the propellerwithout SSD are contrasted. The results show that, under the very same navigational condition,SSD can decrease the cavitation area of the surface of the blade of the propeller. It can beconcluded that SSD does no harm to the cavitation performance of the propeller, while at thesame time increasing the propulsive efficiency of the propeller.