【作者】 王旭东；

【导师】 桑勇；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2019， 硕士

【摘要】 在液压传动领域,溢流阀作为液压系统中必不可少的压力控制元件,应用极其广泛。在定量泵节流调速系统中,溢流阀用来保持系统的压力恒定。溢流阀还可以作安全阀使用,当系统压力由于意外情况而升高时,溢流阀通过排放多余的油液流回油箱,释放系统压力,保护液压系统。锥阀式液压阀由于其具有通流能力强,密封性好,对油液中的杂质不敏感等优势,因此在液压阀中得到了广泛应用,其中锥阀式溢流阀尤为常见,在设计和使用溢流阀的过程中,对于其灵敏度和稳定性等动态特性指标有一定要求,然而其静态特性是已知的,但动态特性往往是未知的。溢流阀的动态特性不仅受实际工作条件的影响,还与阀的结构、设计参数,甚至其所在的液压系统的构成有关,因此本课题在基于双向流固耦合的条件下,针对可能影响锥阀式溢流阀动态特性的关键因素全面、系统地进行分析,旨在通过CFD仿真探究锥阀式溢流阀的动态特性,提高溢流阀的设计水准,为溢流阀的结构参数优化和使用提供参考,具有一定的理论意义和实际应用价值。首先,通过阅读国内外相关文献,掌握关于溢流阀的研究现状,对溢流阀进行了受力分析和运动分析,对CFD数值模拟中使用到的基本理论、湍流模型、动网格技术和相关编程函数进行介绍,并根据溢流阀在工程应用中的实际使用情况确定了边界条件。其次,建立了作为先导级使用的锥阀式溢流阀的几何模型,重点研究工作条件的影响,分别研究了其在不同卸荷压力、不同设定压力和不同给定流量下溢流阀的动态特性,根据CFD分析结果探究了其作为先导级在不同设定压力下阀芯位移变化极其微小的原因,并在小流量和特定卸荷压力下观察到了锥阀的动态不稳定现象。再次,重点研究阀的结构、关键参数的影响,对直接使用的直动式溢流阀建立了几何模型并进行了CFD敏感性分析,确定了所使用的湍流模型,在溢流阀通径为20mm时,通过CFD仿真结果观察到了溢流阀的颤振现象,接着对阀芯的结构进行改进,设计环形阻尼,并通过CFD模拟结果证明了改进的结构可以大大改善溢流阀的动态特性。最后,研究锥阀式溢流阀所在的液压系统中进油管路的影响,对管路-溢流阀组成的系统进行整体分析,分析了进油管路的长度和直径对锥阀式溢流阀的动态特性的影响,发现液压系统中管路的作用与阻尼相似,管路长度的增加和直径的减小都有利于提高阀芯的动态稳定性,并且为通过实验验证CFD仿真结果的正确性,设计了动态特性测试实验方案和数据采集系统。更多还原

【Abstract】 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.更多还原