Design And Performance Study Of Soft Anthropomorphic Hand With Fingerprint-Like Surface Texture

As the key moving part of the control valve,the valve core,plays a decisive role in the precise regulation of fluid flow,pressure,flow direction,etc.However,under the influence of complex working conditions such as high temperature,high pressure,high viscosity and high pollution,the valve core often faces sticking problems,and it is often found only after the control valve moves several times,which seriously affects the core performance of the control valve such as regulation accuracy,seal leakage and action response time.As a typical structural form of control valves,the spool valve,with its long circular shaft valve core structure,is prone to coupled sticking problems under the influence of complex flow,high viscosity media and high pollution environments.Therefore,in-depth research on the sticking formation mechanism and the sticking suppression method of spool valve core will help improve the theoretical system of control valve core design.Supported by the National Key Research and Development Project of China ‘Online Monitoring and Intelligent Control of High-Performance Hydraulic Valve Performance’(Grant No.2021YFB2011300)and Zhejiang Key Research & Development Project ‘Research and Application of Key Technologies for Special Control Valves with High Parameters of ThirdGeneration Nuclear Power’(Grant No.2021C01021),this work focuses on the sticking problem of spool valve cores and systematically studies the sticking formation mechanism of valve core from three aspects: radial unbalance force,uneven thermal deformation and solid particle intrusion into the fitting gap.Based on the sticking formation mechanism,corresponding methods to restrain valve core sticking are proposed.The main research content and results are as follows:(1)Analysis model for transient flow was constructed,and its accuracy and effectiveness were verified experimentally.The influence of working conditions,inlet direction and inlet space angle on the radial unbalance force of the valve core was analyzed.The non-uniformity of the valve core force caused by unbalanced turbulent flow was characterized.The sticking mechanism of the valve core caused by radial unbalance force was revealed.The suppression effect of the valve core flow guiding structure and the eccentric sink groove of the valve body on the radial unbalance force was clarified.The results show that under the influence of unbalanced turbulent flow,the valve core is subjected to unbalanced forces,causing the valve core to tilt around the center of mass,and thus this result in asymmetric changes in the valve core fitting gap.The valve core flow guiding structure and the eccentric sink groove of the valve body can effectively improve the radial unbalance force,thereby slowing down the tilt of the valve core and reducing the probability of valve core sticking.(2)A thermo-fluid-solid coupling model of the spool valve core was established,considering the influence of fluid temperature/pressure-viscosity characteristics on the heat transfer characteristics in the valve.The influence of working conditions and throttle groove structures on the flow characteristics,energy dissipation and temperature distribution in the valve were studied.The uneven thermal deformation of the valve core caused by uneven temperature difference was analyzed,and the sticking mechanism caused by non-uniform thermal deformation was revealed.The results show that when high viscosity fluid flows through the throttle groove,it dissipates energy and causes viscous temperature rise.Different throttle groove structures correspond to different high-speed jets and jet angles,resulting in different viscosity temperature rises.The temperature distribution of the valve core along the circumferential and axial direction is not uniform and the thermal deformation is uneven.The V-shaped throttle groove can homoqenize thermal deformation of the valve core and slow down the asymmetric change of fitting gap.(3)Force-heat-particle coupling sticking force prediction model was constructed for solid particles entering after the asymmetric change of the valve core fitting gap.The influence of inclination angle and thermal deformation of valve core on the radial clamping force of the noncontact valve core were explored.Euler-Euler two-phase solid-liquid flow model was used to study the flow characteristics of solid particles in the non-contact valve core fitting gap.The results show that under the inclination and thermal deformation of the valve core,solid particles of a certain size enter the fitting gap and are squeezed by the valve core and valve body,generating coupling sticking force during the movement of the valve core.The pressure equalizing groove divides the fitting gap into multiple decompression stages with the pressure,which can effectively reduce the radial clamping force of the valve core and help reduce the particle distribution in the sensitive sticking area.The triangular pressure equalizing groove can effectively reduce particle aggregation at the pressure equalizing groove and increase the particle volume fraction at the groove bottom,effectively slowing down valve core sticking.(4)Based on the sticking formation mechanism of valve core,the flow guiding structure optimization design of valve core was carried out by comprehensively considering the force and viscous temperature rise characteristics of valve core.Based on the response surface method,the pressure equalizing groove optimization design was carried out with the leakage of valve core fitting gap and the particle volume fraction in groove bottom as the optimization objectives.The performance comparison experiments before and after the valve core optimization were carried out to verify the improved performance after optimization.The results show that the asymmetric shoulder structure of the valve core with the jet compensating flow guiding structure at the inlet side and the inclined surface flow guiding structure at the outlet side can effectively reduce the steady hydrodynamic force and the viscosity temperature rise at the throttle port.The optimized triangular pressure equalizing groove structure of the valve core reduces leakage and increases the particle volume fraction in the groove compared with the original rectangular pressure equalizing groove structure.The steady hydrodynamic force of the optimized valve core has been greatly reduced,with a maximum drop of 60.7%,which helps optimize the valve core control strategy and makes its control more stable.