Research On The Propulsive And Rotational Characteristics Of Amphibious Vehicle Based On Middle High Pressure Waterjet Propulsion Technology

Excellent maneuvering performance is an important guarantee for the combat capability of the amphibious vehicle sailing on the water. The mid/high pressure waterjet propulsion which adopts the positive displacement pump is a new concept of propulsion. It has the advantages of low noise, high thrust weight ratio and simple structure et al. The aim of this project is to apply the mid/high pressure waterjet propulsion technology to the amphibious vehicle, and then accomplish the vector propulsion of the amphibious vehicle by using the vector nozzle steering mechanism. So as to explore the effect of this new propulsive method to the vector control of the amphibious vehicle through the research and analysis of the maneuverability of it. This paper studies the following aspects:Firstly, the theory of the mid/high pressure waterjet propulsion technology is studied. The influence of structure and performance parameters of water jet propulsion system on the water jet propulsion efficiency is analyzed. Research on the calculation method of the thrust of ideal propeller and actual thruster by using the basic principle of momentum theorem is carried out.Then compare the advantages and disadvantages of several typical steering device, and select the most suitable one to achieve vector propulsion. Afterwards, the whole model of the water jet propulsion device of the amphibious vehicle is selected combined with the structure characteristics of the amphibious vehicle. And the initial matching of the amphibious vehicle model is calculated.Numerical calculation method is adopt to compare and analysis the thrust of the water jet propulsion device with different nozzle contraction angle and different nozzle length diameter ratio, and the sailing resistance of the amphibious vehicle with different nozzle spacing, different nozzle submerged depth and different inlet layout conditions. The optimal results are obtained by simulation, then we can further determine the nozzle structure parameters of the amphibious vehicle model and the distribution of the nozzle and the inlet. At the same time, it will also provide the reference for solving the hydrodynamic coefficient of the amphibious vehicle during the rotation process.Finally, the motion control equation of the amphibious vehicle model is established based on the mathematical equation(MMG model) of the conventional ship maneuvering motion. And the solution of the attached water mass, the inertia moment of the amphibious vehicle and the hydrodynamic coefficient of the viscous fluid is analyzed. Combined with the hydrodynamic calculation of the water jet propulsion system, the mathematical model of the rotational motion of amphibious vehicle is established, and the rotation trajectory of the amphibious vehicle is simulated by Matlab/Simulink at the end of this paper.