Basic Research On The Lubrication Characteristics Of Water Hydraulic Piston Pump

Reconnoitring and developing the sea resource requires the advanced working equipments, which can not only adapt the dicky environment such as the high pressure, low temperature, darkness and anoxia, but also endure the erosion and denudation of the sea water. Using the tap water or sea water as the working media, water hydraulics has many advantages such as environment-protection, safety and easily getting the working media. The sea water hydraulics directly uses the sea water as the working media which transmits the power, which is the ideal driving system of the sea working equipments because of its environment-protection and easily maintenance.Because the (sea) water has strong erosion, low viscosity and poor lubrication, the (sea) water hydraulics are faced with many technology difficulties such as the erosion, leakage and wear of components etc. According to the literature searches and the analysis on them, it is found that there is almost no basic research on the fluid lubrication characteristics of the key friction pairs of water hydraulic pump, which, however, has very important effect and sense on the design of it. Therefore, in this thesis, the complete research of the basic theory and experiment on the key friction pairs of the (sea) water hydraulic piston pump such as the slipper and piston pairs are performed and the new slipper and piston pairs with great lubrication characteristics are presented.Because the viscosity of the sea water is very low, the leakage flow if further large for the water hydraulic friction pairs with the same oil hydraulic friction pairs. In order to achieve the further good integrated performance for the water hydraulic slipper friction pairs, the effect of the short damping orifice in the slipper is used to balance the contradiction between the water film thickness and the length of the acerose damping orifice. Furthermore, the principle with the mixed hydrostatic and hydrodynamic bearing is used to present a new kind of slipper structure which has further great bearing lubrication performance. In the gap flow field of the sea water hydraulic component friction pairs, the inertia force can't be ignored because it has the same quantitative rank as the viscosity force. So, the classic Renolds equations can't be directly used to calculate the lubrication performance of the water hydraulic friction pairs. In this thesis, based on the N-S equations, the analytic and CFD methods are used to research the inertia effect on the water hydraulic slipper and piston pairs and analyze the inertia effect on the flow rate and pressure characteristics for both friction pairs. At the same time, the roughness effect on the lubrication flowing conditions and leakage flow is researched which is in favor of understanding accurately the lubrication mechanism of water hydraulic friction pairs.For the common slipper, it's anti-turnover ability is further poor so that the more strict requirement on the material and surface disposal is presented. Based on the multi-cavity individual hydrostatic bearing principle, a new kind of slipper is presented, on which several hydrostatic bearing structures are set individually. When the slipper inclines, the pressure in the small gap increases and that in the large one decreases, which can produce a moment. Based on the anti-turnover mechanism, the water hydraulic slipper with three cavity individual bearing is designed. For the common slipper structure, the new slider and other kinds of sliders, CFD is used to calculate the ability of its anti-turnover. The calculating results indicate that the three cavity individual bearing slipper has more good anti-turnover ability.Piston friction pairs are one of the key friction pairs of water hydraulic components such as the pump and valve. In the water hydraulic axial piston pump, some wear possibly exists between the piston and the piston hole even the chucking phenomenon can happen because the bearing force of water film makes the piston to incline in the piston hole. Furthermore, because the manufacturing errors produce that the piston and the piton hole have certain ellipse so that the radial gap of piston friction pairs is unequal, the widening bit by bit flow gap can exist in the flow field so as to push the piston to move toward some direction and lead to the chucking phenomenon. In order to improve the anti-chucking ability of the piston, the double damping piston friction pairs are presented based on the hydrostatic bearing principle. In the new piston friction pairs, water reaches the bearing gap after flowing the orifice and supporting cavity and then flow out of it so that the hydrostatic structure can be formed which make the water film have certain ability of resisting the variation of loading. In this thesis, the analytic method is used to deduce approximately the anti-chucking mechanism of the piston friction pairs. Based on the anti-chucking mechanism, the double damping piston is designed. Furthermore, the CFD tool is used to calculate and analyze the flow field of the piston friction pairs which indicates that the new piston has certain anti-chucking ability.In order to verify the theoretic research results, the three-cavity individually supporting slipper and the double damping piston are both designed and manufactured for experiment including that in the test rig and that in the deep sea simulative cabin. On the test rig, the experiments including the inertia effect, surface roughness effect, the anti-turnover comparison of slipper and the anti-chucking ability of piston are mainly performed; in the deep sea simulative cabin, the wear comparison experiments of slipper friction pairs and piston ones are mainly performed.At last, the research results of the lubrication characteristics of the key friction pairs of the water hydraulic axial piston pump are summarized mainly including the mechanism research of the effect of the inertia and surface roughness on the lubrication characteristics, the improving mechanism and new structures of the slipper and piston friction pairs. The research results are helpful to understand and analyze the lubrication mechanism of the water hydraulic friction pairs more accurately, and the presented water hydraulic slipper and piston have further great lubrication characteristics proved by the experiments.