Analysis Of Efficiency Characteristics And Research On Gradual Reliability Of Axial Piston Pump

Since energy conservation and environmental protection have become hot topics in present social development,our country has determined goals for “the dual carbon.” For the hydraulic transmission system with high power and high energy consumption in the equipment manufacturing industry,improving energy efficiency and reducing energy consumption will inject new kinetic energy into its green development.As an important energy conversion device in a hydraulic system,the efficiency and reliability of the axial piston pump during operation process directly affect the performance and service life of an entire hydraulic system.Since hydraulic failure accounts for a relatively large proportion of electromechanical and hydraulic equipment,no expense should be spared when choosing the imported axial piston pump,ensuring the safe and reliable operation of the equipment,the aforementioned seriously restricts the development of the large domestic equipment manufacturing industry.Since the domestic axial piston pump research foundation is relatively weak.Therefore,the investigation of new theories,new technologies,and new methods to improve the efficiency and reliability of the piston pump has significant engineering application values for the green development of the Chinese equipment manufacturing industry.With the rapid development of the axial piston pump towards high pressure and large flow,the loss of efficiency caused by leakage and friction cannot be neglected.Establishing an accurate instantaneous efficiency physical model of the piston pump is helpful in improving the energy conversion efficiency of the piston pump in the design phase.The efficiency of the axial piston pump gradually decreases towards the end of its life with the wear accumulation of the friction pairs,which shows a gradual change.Furthermore,there are various random uncertain factors(such as operating conditions,structural dimensions,and material characteristics)in the piston pump’s engineering practice of the piston pump,which often directly affect the performance and reliability of the pump.Therefore,the gradual reliability analysis method of the piston pump based on the theory of probability and statistics is more suitable for the engineering practice.To solve the problems mentioned above,the main research contents are as follows:(1)The problems of clearance leakage and friction loss can be found in the friction pairs of piston pumps during operation.the instantaneous clearance leakage and friction torque loss of a slipper pair,piston pair,and valve pair in a piston pump are analyzed and modeled in detail to improve the efficiency of the piston pump.Combined with the instantaneous theoretical flow rate and theoretical torque,the instantaneous physical models of the volumetric efficiency model,the mechanical efficiency model,and the overall efficiency are established.Moreover,the accuracy and effectiveness of the established model are indirectly verified by the HYDAC PPV103-10 pump test data.The results show that the efficiency significantly fluctuates with cylinder rotation and that the number of pistons determines the fluctuation period.The minimum of overall efficiency occurs at a cylinder rotation angle of 180°/N,and the angle is the key reliability analysis concern.(2)The volumetric,mechanical,and overall efficiencies of the axial piston pump are selected as reliability failure criteria.Considering the randomness of operating conditions and structural parameters,an efficiency reliability design method for piston pumps is proposed by employing probability statistics theory,random perturbation method,and fourth-order moment technique.In addition,the accuracy and timeliness of the proposed method are verified by the Monte Carlo random simulation.The reliability sensitivity technique is used to quantitatively evaluate the influence trend and degree of random variables on the reliability.Since the overall efficiency model is highly nonlinear,the operating conditions significantly impact the reliability sensitivity.A robust optimal design method for the overall efficiency reliability of the axial piston pump is proposed based on the sensitivity analysis.The optimization design results show that the efficiency reliability requirements are met,the overall mass of the piston-slipper group is lowered,and the sensitivity is significantly reduced,reaching the target of lightweight and robustness after the reliability robust optimization design.(3)The slipper pair in the axial piston pump,prone to wear and degradation,is selected as the research object.According to the test and analysis of the worn slippers,the two-body abrasive wear and the adhesive wear are the main wear forms.Based on the elastodynamic lubrication model of the seal belt of the slipper pair,the mixed lubrication and the boundary lubrication models of the slipper pair are established by using the Hertz contact theory,surface roughness peak contact theory,and Greenwood Williamson model.Based on the two-body abrasive wear model and the Archard adhesive wear model,the discrete partial wear prediction method of the slipper pair is improved.Moreover,the relationship between the influencing factors and the partial wear is analyzed,and the gradual change process of partial wear of slipper pair is explored.The results show that the wear depth and the wear width of the outer slipper sole edge are positively correlated with the oil discharge pressure and the tilt angle of the swash plate,and negatively correlated with the rotation speed and the oil viscosity.The slipper pair performance periodically fluctuates with the rotation angle of the cylinder block,and the average oil film thickness,leakage flow,and friction torque show a gradual trend with time evolution.(4)In order to solve the calculation efficiency problem of numerical simulation in gradual reliability analysis,the mapping relationship between the performance parameters of the slipper pair after wear and the design variables is established by using Kriging surrogate model.Then,the numerical simulation can be replaced in the analysis of gradual reliability.Firstly,the Kriging surrogate model is used to fit the efficiency test data samples of the axial piston pump.The applicability of the surrogate model for predicting the efficiency of the pump is verified by comparison and reliability analysis.The Sobol sequence is used to sample the design variables,and the wear patterns of the samples are simulated and substituted into the mixed lubrication and the boundary lubrication model of the slipper pair.The leakage loss and friction torque loss of a single slipper pair are taken as the response values of the Kriging surrogate model.Then,the mapping relationship between the response of a slipper pair performance parameters and random variables is established.Gradual reliability and reliability sensitivity of the piston pump efficiency are analyzed via the gradual reliability Monte Carlo method and the extreme value method.The analysis results show that the reliability of the piston pump efficiency gradually changes with time.The sensitivity analysis shows that the piston pump tends to be reliable when running for a relatively long time,characterized by small swash plate inclination(small displacement),low pressure,high speed,and high oil dynamic viscosity.