Design And Simulation Of An Electric Driven Waterjet Propulsion

Compared with the propeller,the waterjet propulsion has the advantages of strong cavitation resistance and high efficiency at high speed,and waterjet is becoming more and more widely used in high-speed ships.But the waterjet propulsion also has some disadvantages,such as the long shafting,the need for special space to install power machines and the need for an astern system.To solve the problems of the waterjet propulsion,the paper use for reference the structure of POD electric propulsion system and propose a new type of no-shaft electric driven waterjet propulsion system.In this paper,a new type of electric driven waterjet propulsion structure is introduced.the high-speed motor is directly integrated in the axial flow pump,and then the whole structure can be directly hung on the ship through the rotary device.The direction of the ship can be changed by changing the direction of the water jet.The whole structure is compact,and the mechanism design of water jet driving direction adjustment is simplified,and the flexibility of waterjet propulsion is effectively improved.Numerical simulation of the waterjet propulsion is made by means of CFD software and the influence of the new structure on the efficiency of the waterjet and the influence of the other parameters are studied.The results show that the efficiency of the electric driven waterjet propeller can reach the level of the general axial flow pump,but the high efficiency area is narrow and the efficiency of the saddle area decreases rapidly.In addition,the blade angle of the impeller has a strong impact on the pump head,and the support plate is also one of the reasons for the decline of the efficiency of the electric drive waterjet propeller,but the effect is small.In the waterjet propeller,the motor is cooled directly by using seawater.In the paper,the cooling system is simulated.The influence of the shell thickness and the velocity of the seawater on the cooling system is studied.The results show that the cooling system can meet the demand of motor cooling;the cooling performance of the wanterjet propeller can be improved by decreasing of the motor shell thickness,and the amplitude of variation is uniform;the cooling performance can also be improved by increasing the water flow velocity,but the amplitude decreases with the increase of velocity.