| Considering the front R&D direction in the field of fluid power all over the world, In this dissertation, the seawater hydraulic pump, the heart of seawater hydraulic systems, is selected as the research project, and the objective is to develop a seawater hydraulic pump lubricated by seawater and with the pressure 14MPa and the flow rate 40L/min. Aimming at the key technical problems and its solutions faced with the seawater hydraulic pump, such as severe corrosion, friction & wear, leakage, cavitation, contamination and so on, the research method combined with theory study, computer modeling & simulating, and experimental research is used in this dissertation. After the axial piston type with check valves is confirmed as the main structure of seawater hydraulic pump, a set of dynamics and kinematics basic theory and modeling formulas about it is systemically established. Focus on the key and important parts of the seawater hydraulic pump, such as the check valves, cylinder bore and piston pair, slipper pad and swash plate pair, bearing pairs, etc., for improving the response characteristic and flow capability of the check valve, reducing the pv value between friction pairs, taking full advantage of the supporting, lubricative, and cooling ability of seawater pressured, selecting the friction pair's materials with self-lubrication and antiwear characteristics, the design theories and methods, structures, and material selection about the key and important parts are carefully systemically investigated. And, large numbers of friction pair specimens are designed, fabricated and tested on the friction & wear test rig made by HUST, and the optimized solutions of seawater hydraulic pump's key technoloies have come out. Based on above, the first seawater hydraulic pump lubricated by seawater and with high pressure is developed in China. The achievements of this dissertation as follows: (1) successfully using a flat valve as the check valve for the seawater hydraulic pump, and made the valve core of polymer composite at first in China. This check valve have advantages of good sealability, high flow capability, rapid response, low noise and vibration, and easy manufactured, etc. (2) A new joint structure combined slipper with a anti-erossion alloy sphere socket and piston with a half nonmetal sphere head for piston and slipper joint pair was put forward, it solved the tribological problem of piston and slipper joint pair under heavy stress and lackage lubrication of seawater effectually. (3) A new slipper structure of slipper body made of anti-erossion alloy with slipper pad made of nonmetal, and a design theory for slipper pad using a integrated residual load design method and complete fluid pressure support method were put forward. It effectually solved the tribological problem of swashplate and slipper pair with seawater lubrication and under heavy stress and high speed. (4) Designed successfully a new structure and the mate clearance for cylinder bore and piston pair that the piston made of stainless steel with a weld stellite surface layer and the cylinder bore made of polymer composite with a fixed mate length to piston. It solved the problems of scrape each other, friction&wear, and leakage to the cylinder bore and piston pair under the boundary or non lubrication. (5) Successfully developed a seawater hydraulic pump with seawater lubrication and high pressure at first interiorly, after thorough experimental researches, it shows the performance of flow rate of 40.2L/min, volumetric efficiency of 81.9%, mechanical efficiency of 86.6%, total efficiency of 70.9% at the delivery pressure 14MPa and rotate speed 1000r/min. This achievement supply a gap at home, and shorten the level difference between home and international advanced technology on seawater hydraulics. Further more, the author has attained a inventive patent of this seawater hydraulic pump and an applied new type patent of the new slipper-piston subassembly optimized design and structure and materials with above achievements of (2) and (3). The seawater hydraulic pump developed by author can meet many urgent application needs in the field of ocean exploitation, under water operation, seawater desalination, fire fighting in naval vessels, and navy equipment, it has a very wide foreground of application. The successful base theories and experimental research experiences about this seawater hydraulic pump with seawater lubrication can be used to develop seawater hydraulic pumps with higher delivery pressure and performance, and also can be used for fresh water hydraulic pumps and motors directly, The design theories, methods, new structures and materials about the key friction pairs of the seawater hydraulic pump with seawater lubrication can be used for oil hydraulic pumps and motors.
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