Research On The Dynamic Characteristics Of The Conical Poppet Pressure Relief Valve

In hydraulic fields,Pressure relief valve,which is an indispensable pressure control element,is widely used in hydraulic industry.The pressure relief valve is utilized to keep the system pressure constant in a flow-restricted speed regulation system.The pressure relief valve can also be used as a safety valve.The pressure relief valve pops up discharging the overflow pressure into the oil tank to protect the hydraulic system as the system pressure increases duo to some unexpected situation.The most extensively used form of spool in hydraulic industry is conical valve,which has the advantage of strong flow capacity,good sealing performance and insensitive to the contamination in the oil.And the conical poppet pressure relief valve is particularly common.In the process of designing and using the pressure relief valve,there are certain requirements for its sensitivity,stability and other dynamic characteristics.However,though the static characteristics are known,the dynamic characteristics are unknown in advance.The dynamic characteristics of the conical poppet pressure relief valve can not only affected by the actual working conditions but also affected by the valve structure,key parameters,or even the constitution of the hydraulic system in which it is located.Thus the key factors that may affect the dynamic characteristics of the conical poppet pressure relief valve are systematically studied in this project based on the two-way fluid-structure interaction.The research object of this project is to improve the design technology by investigating the dynamic characteristics of the conical poppet pressure relief valve through CFD simulation and to provide a reference in practical engineering application for designing effective and high performance pressure relief valve,optimizing valve structure and parameters,which is significant and valuable in theory and application.Firstly,a good knowledge of the research status of the pressure relief valve is acquired by reading relevant national and international literature.Moreover,the force analysis and motion analysis on the pressure relief valve is carried out.The basic theory using in the CFD numerical simulation,turbulence model,grid technology and related programming function are introduced and the boundary condition is determined according to the actual situation in engineering application.Secondly,the geometric model of a small conical poppet pressure relief valve which is used as a pilot valve is established,focusing on the impact of the working conditions.The dynamic characteristics of the conical poppet pressure relief valve are studied under different unloading pressure,setting pressure and constant flow rate,respectively.The reason why the valve core displacement variation is extremely small used as a pilot valve is investigated according to the simulation results.The dynamic instability phenomenon is observed under low constant flow rate and specific unloading pressure.Thirdly,the emphasis is put on the valve structure,design parameters of the pressure relief valve.The geometric model of the direct-operated conical poppet pressure relief valve is established and the CFD sensitivity analysis is conducted.The used turbulent model is determined.The chatter phenomenon of the conical poppet pressure relief valve can be observed as the nominal diameter size is increased up to 20 mm through CFD simulation results.And then the structure of the valve core is modified to design the annular damping.It is proved that the modified structure can greatly improve the dynamic characteristics of pressure relief valve through CFD simulation results.In the end,the impact of damping clearance,spring stiffness,degree of pressure changes on the dynamic characteristics of the pressure relief valve is investigated.Finally,the impact of the constitution of the hydraulic system in which it is located is studied.The pipeline-pressure relief valve system is investigated as a whole.The impact of the parameters such as pipeline length and pipeline diameter on the e dynamic characteristics of the conical poppet pressure relief valve is investigated.And the simulation results show that the effect of the pipeline is similar to the damping in hydraulic system.The increase of the pipeline length and the decrease of the pipeline diameter are beneficial to improve the dynamic stability of the valve core.And in order to verify the correctness of CFD simulation results through experiments,the dynamic characteristic test scheme and data acquisition system are designed.