| Aiming at solving the serious leakage and abrasion problems of traditional high water-based hydraulic motor working under conditions of low speed,high pressure and high water-based hydraulic fluid(HWBHF)lubrication,and promote the study and application of high water-based hydraulic motor(HWBHM).The key technologies in low speed,large torque,and HWBHM under low speed,high pressure and HWBHF lubrication conditions were studied,which based on the program supported by National Natural Science Foundation of China(51675519)“Design theory and key technology of swiveling cylinder type HWBHM with high pressure low speed and large torque for mine”.In this paper,valve distribution mode was proposed to use in HWBHM,and swing cylinder structure was applied to alleviate the abrasion between piston and cylinder.The study mainly focuses on the study of key structure optimization,materials matching of friction pairs,and the purpose of this study was to analysis and solve the problems of abrasion and leakage for key frictions in HWBHM.During the study,methods of theoretical analysis,simulation analysis and experimental study were combined,which aims to lay the foundation for the design,manufacture and application of HWBHM.First of all,in view of the working charcteristics of low speed,high pressure and large output torque,mainly strcture parameters of new type self-balanced valve distribution mode(SVM)HWBHM were designed and optimized with the purpose of reducing the ripple of displacement and torque.By establishing the mathematical model of self-balanced distribution valve(SDV),orthogonal test was implemented to study the influence regulation of working parameter and structure parameters on distribution performance,in which valve’s opening and closing stability and pressure drop in SDV were chosen as evaluation indexes.Simutanously,the optimization of valve parameters were realized.Based on the optimized parameters of HWBHM and valve parameters,distribution performances of SDV was studied by theoretical method.Besides,the AMESim model of HWBHM was established to simulate the pressure,flow and load characteristics of HWBHM,and the feasibility of optimized HWBHM’s parameters and SDV’s parameters was verified.Secondly,for the requirements of well friction properties and anti-corrosion for matching materials in HWBHM,experimental studies on friction and wear of mating materials with different paring materials were implemented based on material friction and wear theory.The optimization of mating materials was realized,and the influence regulations of low speed,high pressure and HWBHF lubrication conditions on the friction coefficient,wear rate and surface topography of mating materials were revealed.The study results showed that:under working condition of low speed,the main failure mode of friction pairs stainless steel(SS)/SS and SS+surface engineering material(SEM)/SS+SEM is abrasive wear,while the main failure modes of friction pairs SS/PEEK-30CF and SS+SEM/PEEK-30CF are abrasive wear and adhesive wear.Coupling materials SS+OVINO-GIC/PEEK-30CF has the best friction performance,and then is SS+OVINO-GIC/SS+OVINO-GIC.Within the range of HWBHM’s operating parameters,the friction performance of coupling materials would increase with the increase of working speed,while the influence of working pressure on friction performance could be ignored.The study results showed low friction coefficient of0.01~0.05 for coupling materials SS+OVINO-GIC/PEEK-30CF under low speed,high pressure and HWBHF lubrication condition,which could improve the working life and working efficiency of the friction pair.Thirdly,based on the study of matching materials for friction pairs,methods of theoretical research and simulation test were implemented on piston pairs(including piston-crankshaft pair and piston-swing cylinder piar),and the influences of structure parameters,sealing form and coupling materials on the wear friction performance and leakage properties of friction pairs in HWBHM were explored.The study results of piston-crankshaft pair based on slipper pair design theory and numerical simulation indicated taht:if the designed thickness of lubrication film is less than 8μm,the influence of pressure drop coefficient k_αon the leakage of piston-crankshaft pair with rectangle/annular piston chamber is rather small.Compared with annular piston chamber,rectangle piston chamber has the advantage of reducing structure parameters and leakage.The designed k_αand damping hole diameter d_l have great influences on damping hole length l_d,and annular piston chamber has the advantage of reducing d_l that could decrease machining difficulty.The volume efficiency loss caused by piston-crankshaft pair with complete static pressure equilibrium structure is rather large,which is detrimental to the stable and reliable operation of the motor.For residual compression piston structure,serious wear phenomenon always occurred at the chamber edge of piston with rectangle chamber,at the chamber edge and long sealing edge of piston with annular chamber.The study results for piston-swing cylinder pair based on the theory of non-contact clearance seal and the mechanism of contact seal showed that:Sealing length and sealing clearance have significant influences on leakage,and the leakage problem in the piston-swing cylinder pair can be obviously improved by improving the matching accuracy of friction pair.The influence of motor’s working speed on clearance leakage is rather small,while the influences of working pressure and medium temperature has significant influence on the leakage.When the material deformation was considered,the difference of volume efficiency loss between fluid-solid coupling analysis and theoretical analysis would increase with the increase of working pressure and working speed.Compared with Y sealing ring,the application of two-stage combination type Sitefeng seal could reduce the power loss of friction pair.Simultaneous,the sealing area between Sitefeng seal and structure was increasing with the increase of working pressure,while there was little change of contact pressure with the range of working pressure when working at high pressure,which could improve working life.Finally,on the basis of theoretical analysis and numerical simulation,a testing machine was established to study the friction and leakage performances of key friction pairs in HWBHM.Then,experiments for piston pairs(including piston-crankshaft pair and piston-cylinder pair)were conducted on the established test machine,which aiming at exploring the effects of working pressure,speed and structure parameters on friction and leakage characteristics of friction pairs.The experimental results on the structure parameters of piston-crankshaft pair showed that:when piston-crankshaft pair was worn,the serious leakage was at long sealing side for piston with rectangle chamber,and the leakage was almost uniform at four sealing side.The influence of compaction coefficient on volume efficient loss was significant for piston with rectangle chamber,while the influence on piston with annular chamber was not obvious.Furthermore,experimental study was conducted for the optimized piston pair structure and mating materials under actual working condition,and the study results indicated that:when two-stage combination type Sitefeng seal is applied in piston-swing cylinder pair,and compacting coefficient k_y for piston slipper with annular chamber is 1.03,the piston-crankshaft pair with mating materials 316L-GIC/PEEK-30CF presented good friction and leakage properties after a long time friction under low speed and high pressure working conditions.Through the above studies,the key structures’optimization of SVM HWBHM were realized.Meanwhile,the effects of the working condition(high pressure and low speed)on abrasion and leakage characteristics of key friction pairs are revealed,which laid theoretical foundation and technical support for whole machine design of high water-based hydraulic motor with low speed and high torque. |
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