Hydrodynamic Performance Research Of Dual-Ratio Propeller Based On CFD

Trawler vessels are multi-state ship,so conventional propulsion systems can only meet some sailing conditions of it. As a result, the host can not make full use of its rated power when conditions change, which will result a poor matching among paddle,boat and machine. Using the double-ratio gearbox and ducted propeller, which can not only take advantage of the ducted propeller but also can make full use of its rated power in various conditions. So we will achieve the intention that optimization of paddle,boat and machine in multi-state.Ducted propeller has been widely used on trawlers as it can absorb fully the engine power in variable operating conditions and has higher efficiency in heavy loading. In addition, with the development of computational fluid dynamics as well as some commercial software of the method, it is popular to use the CFD software for numerical calculations in the fields of solving complex engineering problems. Because of its advantages, it is popular to more and more people.In this paper, the numerical calculation of fixed duct propeller and rotary duct propeller are carried out with using of software, such as CATIA, GAMBIT, FLUENT and so on. what's more, some parameters of wing-type duct and simple paddle-type duct were analyzed. Finally, the reduction ratio of light-load condition and towing condition are calculated based on drawing and CFD in order to match ship, host and propeller. In the process of numerical calculation, the spatial discretization is unstructured tetrahedral mesh, the difference is a first-order upwind difference, the numerical method is SIMPLEC that is pressure-based coupled solver. What is the thesis'content are following:1. Using the software of CATIA for three-dimensional modeling of the ducted propeller. and using the moving grid method to calculate the hydrodynamic performance of fixed and rotary duct propeller. Then pressure, speed and wake field were analyzed.2. Analysis the propulsion performance of fixed duct propeller with change of the gap between the duct and the paddle blade as well as the change of length of duct. For simple line-type ducted propeller, what I do is analysis the influence of gap between duct and paddle, length of duct,length of entrance and outflow to the propulsion performance of duct propeller.3.Based on the mechanism of dual-ratio propeller, first of all, determine elements of ducted propeller according to the main dimensions. For example, diameter, pitch.number of blades and so on. So the maximum velocity on light loading will be determined as well as speed and pitch. After having known the velocity of towing, suppose the range of speed. So we will calculate curves of force and pitch on different speeds based on drawing. As the ducted propeller is constant pitch,the pitch of light loading is the pitch of towing condition. Finally, we will know the speed and towing force according to the pitch.4.After we have known the speed and velocity on light-load condition as well as the towing condition, we can use the method of CFD to calculate the typical condition of light and towing. Then analysis the performance of different conditions, so as to determine speed of dual-ratio ducted propeller on light-load and towing condition.