| When the hydraulic pump is operated in ocean-depth,it faces extreme environmental conditions such as high pressure and low temperature.These environmental parameters will affect lubrication characteristics of port plate pair,which is one of the key friction pairs,this will affect performance and working life in pump.For this reason,the lubrication characteristics of piston pump’s port plate pair under varying ocean-depth are studied.In this paper,the CFD simulation is used to obtain the effects of operation parameters,structural parameters and oceanic parameters on dynamic flow field characteristics of port plate pair.Based on the finite element analysis of distribution substructure deformation,oil-film thickness superposition method is used to predict the lubrication characteristics.It provides the reference for the property analysis and the structural design of port plate pair in pump under varying ocean-depth condition,which is of great significance for engineering application value.The main contents are as follows:(1)The properties of oil media is researched on oceanic condition.The model of deep-sea working environment is established to analyze the influence of heat loss and other factors on the properties of oil media,which in viscosity and effective bulk modulus on oceanic condition.The results show that oil viscosity,effective bulk modulus and environmental pressure are both positive correlation,however,it has the negative correlation with the change of temperature,which emerges a nonlinear upward trend with increasing ocean-depth.(2)The lubrication characteristics of port plate pair are analysed in ocean-depth.The wedge-shaped pressure field of oil-film and the force distribution characteristics of port plat pair are derived with the change of properties of oil media.The heat-flow coupling model and the elastic deformation model are established considering the effects of different oceanic pressure and temperature.Studying the influence of lubrication characteristics such as the field of pressure,temperature and velocity in port plat pair depends on sea-water.(3)The distributed law of oil-film lubrication characteristics are revealed with the change of operating parameters and environmental parameters,which provides the reference for structural optimization of port plate pair.By extracting the fluid domain model,the CFD simulation is used to analyze the regulation of oil-film lubrication characteristics.It indicates that the pressure field of common port plat pair shows a significant negative pressure at the top dead center,and the bottom dead center is an ultra-high pressure,which seriously affects the operation of pump and has poor lubrication characteristics.Under conditions of lowpressure,swashplate angle and small speed,the design of damping the groove structure can buffer oil pressure,eliminate the phenomenon of oil-film negative pressure and ultra high pressure,oil-film stability increases,the lubrication characteristics are better.With the increase of water depth,lubrication characteristics of port plat pair are deteriorated,and fluid lubrication is difficult to form when driving depth in[3000m,7000m].(4)Taking oil-film lubrication characteristics into account when the distribution substructure is deformed.The deformation model of port plate pair is constructed to study the finite element analysis of deep sea distribution by means of ANSYS software.It declares that the total deformation of port plate pair formed by plate and cylinder block are much smaller than oil-film thickness in atmospheric conditions.That is,the structural deformation has little influence on oil-film thickness field,so the lubrication characteristics are better.As the increasing of water depth,axial deformation of cylinder high-pressure oil groove sealing belt increases non-linearly.Oil-film in high-pressure zone is thin,the transition zone is thick,and low-pressure zone is centered,however,the outer seal band is deformed more than the inner seal band,oil-film present out-thin,inner-thick,and the distribution is uneven,which form an "umbrella" oil-film.The deformation of the sealing band of port plate plate increases linearly.Oil-film is the largest in high pressure oil groove,the low pressure oil groove is the smallest,and the transition zone is moderate,so the outer ring is thick and the inner ring is thin,forming a "hem" phenomenon.Considering structural deformation of port plate pair,the deformation of cylinder is larger than plate.The thickness of integrated oil-film is thin,the transition zone is thick,and low pressure zone is centered,it is distributed in the radial direction and is not easy to form.At the water depth in [0m,5000m],oil-film lubrication characteristics are good,and in the depths of [5000m,7000m],lubrication characteristics are poor.When the water layer exceeds 710 m and 736 m respectively,the stress of the port plate pair is too large,the cylinder block(QT500-7)and the port plate(38GrMoAl)material is not applicable,it is necessary to use a composite pressure-resistant material. |
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