外文翻译--润滑和摩擦学在海水水力活塞泵中的应用
附录二 外文翻译英文文献lubrication and tribology in seawater hydraulic piston pumpAbstract: Water hydraulic systems have provoked major interest because of the human friendly and environmental safety aspects. Piston pump is one of the most frequently used hydraulic units in recent engineering technique.In water hydraulic piston pump,poor lubrication is more likely to happen than in oil hydraulic one because of difference in properties between water and oil.So there are some key problems such as corrosive wear and erosion,which are investigated briefly.Many new materials have been developed,which give longer life expectancies with water without corrosion and erosion.A new type of seawater hydraulic piston pumps with better suction characteristics had been developed at HUST.Much of this research has concentrated on new materials,structureand experiments,which are also specially introduced.Keywords: water hydraulics;pistonpump;lubrication;test;materialINTRODUCTIONThe earliest hydraulic systems used water as the hydraulic fluid.This restricted the working temperature range and caused corrosion as well as lubricating problems.It was not until the late 1920's that mineral hydraulic oils were introduced.Consequently, the oil became the main pressure medium of hydraulic applications.Recently,the demand for usingpure tap water(excluding seawater) as a pressure medium in hydraulic applications has increased due to its availability,easy maintenance,its low cost and high safety levels against pollution and fire hazard.So,water hydraulics can be used in new application areas such as food processing,pulp and paper industry,medicine,glass making,coal mining and nuclear industry.Water is characterized by very low viscosity in comparison with mineral hydraulic oils.For example, the kinematics viscosity of water at 40 is about 0.7 /s and of typical mineral oil is 3 2 /s. Key problems should be considered in water hydraulic system. Firstly,the very low viscosity must increase the difficulty of developing hydrodynamic film between frictional pairs,and the very small change of water's viscosity with pressure means that elastohydrodynamic lubrication with hard materials is unlikely to occur.So,the low viscosity is accompanied with poor lubricity of water.Poor lubricity can cause corrosive wear and erosion problems.Secondly,it is to be noted that water (especially sea water)is electrically conductive and may act as anelectrolyte when impurities or certain additives are present.In such cases the electrolytic corrosion may occur.Therefore metallic materials to be used in connection with the water pressure medium should comply with the electrochemical series.From the present point of view,oil has an advantage against water in the aspect of lubrication but the recent technology of materials,designs and tribology has brought the possibility of using water as a pressure medium again.A number of new materials,such as stainless steel,corrosion resistant alloy,ceramics,polymers,bronze,brass,anodized alumina and composites,etc.,have good compatibility with water,along with modern design and manufacturing techniques,water hydraulics become more and more practical.Modern science and technologies can provide essential technical guarantee for the reemergence and development of water hydraulics. Piston pump is one of the most frequently used hydraulic units in recent engineering techniques.In water hydraulic piston pump,poor lubrication is more likely to happen than that in oil hydraulic oneIn water hydraulic system,the first objective is to develop piston pump and motor using raw water as pressure medium.To deal with problems of using raw water as lubricant,three critical sliding pairs,such as the cylinder block/port plate,piston/cylinder bore,swash plate/slipper pad have been focused.Water piston pump(motor) has been developed in some developed countries,such as USA,UK,Japan,Denmark,GermanyandFinland,etc.Pumps and motors are virtually identical.The Fenner company in the United Kingdom has developed an axial pump for raw water with fixed displacement.The pumps and motors are of the swash plate type.Bearing centers are designed to be in line with the torque centers of the units in order to minimize tilt forces on the valve plate.All rubbing surfaces use polymer-stainless interfaces.An adapt ation of the pump using ceramic pistons has operated successfully up to 14MPa.The casing are made of stainless steel.The Hauhinco radial piston pump in Germany has fixed displacement.The pump design is based upon using new and non-traditional materials sothat a separate lubrication system is avoided.The medium,industrial water,to be pumped also acts as a lubricant.Typically pump ratings are: flow rate up to 242L/min,pressure up to 32MPa.The Danfoss Nessie pump of type PHA(pump axialhigh-pressure) in Denmark is designed as an integral unit based upon the swash plate principle.All friction surfaces,such as cylinders,thrust plate and piston shoes