【作者】 郑淑娟；

【导师】 权龙；

【作者基本信息】 太原理工大学 ， 机械工程， 2015， 博士

【摘要】 社会需求是推动技术发展的强大动力。液压技术飞速发展，要求液压系统满足高压力、大流量，但体积小、重量轻，且高精度、高效率，液压插装阀技术在此形势下应运而生，二通插装阀的出现使液压技术的发展提高到了一个崭新的阶段。在某些应用场合，插装阀是提高生产力和竞争力的唯一选择。液压阀相关的科学问题，各类型液压阀的流量特性、作用在阀芯上液动力的大小和方向、液动力对阀工作可靠性、操作灵活性和动静态特性的影响、内部流场的可视化计算等，一直是流体传动与控制技术领域中的基础研究问题，也是发展高性能液压控制阀必须解决的关键问题。锥阀作为插装阀的主要结构形式，通过研究发现，现有理论有待进一步研究解决完善。阀口过流断面面积直接影响阀过流特性的计算，但关于锥阀过流断面计算公式的现有理论尚存在问题。阀芯带锥但锥面不完整的锥台形锥阀和阀座带锥的锥阀在计算流量时采用按完整锥面锥阀导出的过流面积计算公式，会造成非常大的计算误差。从过流断面的定义出发，利用CFD流场可视化技术对锥阀的流场进行深入细致地研究分析，找出了其在整个大行程范围内不同开口度时的过流断面位置。在研究中发现在小的阀芯行程范围内传统过流断面面积计算公式仍适用，若阀芯行程较大，传统公式不再适用，且内外流不同流动工况时流动特征出现很大的差异。首先确立传统公式适用的临界开口度，推导了不同行程时的过流断面面积计算公式。并指出阀口锥部导流作用不同，局部损失不同是造成内外流流动特征差异的根源。阀口的抗气蚀特性也是阀口节流性能好坏的一个重要指标，但判断空化初生的标准目前尚未统一。通过分析液压阀内液流流动过程，追溯空化产生根源，提出了压力恢复系数表征不同阀的抗气蚀能力。液动力对阀的动静态特性关系甚大，是设计液压阀需考虑的重要因素。液动力计算公式是液压系统特性建模重要的基本方程之一，对液压系统的特性有很大影响。阀芯开口度大时，锥台形锥阀和阀座带锥锥阀过流断面的位置和计算发生变化，传统的理论公式对其液动力的计算也不再适用。液动力本质上是流体运动所造成的阀芯壁面压力分布发生变化而产生的，故从流场分析入手，获得阀芯底部压力分布值，将压力相对作用面积积分，得到其液动力值，这是最直接的计算方法，且可细化流场信息得知液动力产生的机理。为了便于工程实际使用，根据流场分析得出的液动力产生的主要因素，结合控制体积的选取原则，对于不同阀口形式锥阀，内外流工况不同时，选取不同的控制体积。根据动量定理推导出的相应的计算公式，最终给出了不同流动方向下阀口全行程时的液动力特性，精确度更高。传统的液动力计算公式中，液动力与进出口压力差值成正比，与进出口压力值的大小无关。但锥阀进出口压差相同，进出口压力值低时，阀内流动状态变为两相流，与单相流的流动特征不同，故需对传统公式进行修正。提出用临界进口压力值和临界出口压力值来区分阀内液流不同流动特征。利用全空穴模型对阀内流场进行了两相流模拟仿真，分析阀内流场压力分布，明确相同进出口压差，不同进出口压力值时液动力区别的真正原因，对传统公式进行修正，推导出了适用于两相流状态下液动力的计算公式，并利用已有的试验数据进行了验证。液压技术遍布整个工业控制领域，包括一些高科技领域，为了达到更加精准的控制，对控制元件的特性要求将更加苛刻。因此在研究插装阀流量特性时，考虑阀套和阀芯变形对于节流口过流面积及阀套阀芯间配合间隙的影响，将是液压元件设计理论不断完善化所必须的。建立实际使用的插装阀整体三维模型，包括阀芯阀体阀套，进行了插装阀液固热耦合分析。首先根据液压阀流体流动过程的传热特点，对液流流动过程流场、温度场进行数值模拟，得到整个锥阀固体、液体区域内详细的温度场分布规律，最后给出热应力和液压力共同作用下的阀套阀芯变形量。分析表明阀芯阀套的变形对于阀芯阀套的配合间隙有一定的影响，但两者的作用根据锥阀工况的不同，会有很大的变化，在实际过程中应该针对典型工况进行具体分析；阀芯阀套的变形对锥阀节流特性的影响一般可以忽略不计。对阀整体的流固热耦合分析在一定程度上可科学估算变形量对阀套阀芯配合间隙及阀口特性的影响，从而为阀套阀芯设计提供可供参考的依据。最后搭建了插装阀流量特性和动态特性测试试验台进行试验研究。测试阀在不同压差，不同开口度的稳定流动时的流量特性，验证过流断面面积计算公式的正确性。建立阀的AMEsim仿真模型，结合推导出的液动力公式和过流断面面积计算公式进行模型参数设置，模拟阀的阶跃响应；给定阀不同阶跃信号，测试阀的阶跃响应。将阶跃响应的仿真值和试验值进行比较，结果表明采用提供的液动力公式得到的计算结果是可信的。以上研究成果进一步完善了有关液压阀流体力学的基本理论，给出了能准确描述锥形插装型主阀在大行程范围内阀芯所受液动力的计算公式、锥阀过流断面面积的计算公式，为从机理上建立液压阀准确的数学模型进行非线性数字仿真研究提供了一定理论基础并具有一定的工程实用价值。更多还原

【Abstract】 The social demand is the powerful engine for the technology. Hydrauliccartridge valve is the product of the rapid development of hydraulic technology,which requires higher pressure, larger capacity but smaller size, lighter weight,higher precision and efficient. Two-way cartridge valve raise the hydraulictechnology to a new stage. In some applications, the cartridge valve is the onlyoption for improving the productivity and competitiveness.The basic research problem includes the flow rate characteristics, flowforce and its influence for the static and dynamic characteristics, visualization offlow fields. The key for higher performance of the hydraulic valve is also tofocus on those fields. The poppet cone is the main structure form of cartridgevalve. The existing theory for poppet valve needs to be further studied toimprove.The cross section area is the key of the calculation of the flow rate. Theexisting theory about the cross section area has some problems. It exist theinaccurate that the area formula derived through the full cone poppet valve isadopted for the truncated valve and the cone-seated valve. Based on thedefinition of the cross section, its position varied the cone at the differentopening is identified when the cone moves over the large stroke through CFD visualization of flow fields. It shows that the traditional formula can be adoptedfor the cone moving over the small stroke, but is inadequacy for the conemoving over the large stroke. The divergence flow is very different from theconvergence flow. The formulas for the critical opening and the cross sectionarea are derived. It is found that the cone diversion is the main factor for thedifference of the flow characteristics in the convergence and divergence flow.The anti-cavitation ability of the orifice is an important index of the throttlingperformance. As the judgment standard of the cavitation inception has not yetunified, the pressure-recovery factor is defined for indicating the anti-cavitationability of the orifice through tracing back to the root of the cavitation.The flow force is the important factors to be considered in the design ofhydraulic valve, and closely ties the static and dynamic characteristics of valve.The flow force formula is one of the important basic equation for modeling thehydraulic system, has a great influence on the system characteristics. As a resultof the change of the cross section at the large opening, the traditional theoreticalformula of flow force is uncertain. The change of the pressure distribution alongthe cone is the nature of the flow force. The flow force can be calculated by theintegral of pressure along the cone obtained from analyzing the flow field. Thisis the most direct way. Based on the principles for selection of control volume,combined the main factor of flow rate, the selection of control volume varieswith the different orifice and the divergence and convergence flow condition.The corresponding calculation formula is derived by the theorem of momentum,so the characteristic of the flow force is obtained at full stroke.From the traditional formula of flow force, it can be found that the flow force is proportional to differential pressure, independent of the value of outletand inlet pressure. On the condition of equal differential pressure, the flow statebecomes the two-phase flow when the pressure is low, so the traditional formulaneeds to be amended. The critical pressure is put forward to distinguish betweenthe different flow stations. The three-dimension flow in the valve is simulatedby using full cavitaion model. The formula of the flow force is amended basedon the difference of the flow station made clear by analyzing the flow field. It isverified by existing experimental data.The hydraulic technology is widely used in the industrial control field,including some high-tech. In order to achieve more precise control, theperformance of control elements will be more demanding. The deformation ofthe sleeve and valve cone maybe has influence on the cross section area and fitclearance between them. Therefore, for the constant perfection at designing ofvalve, it is need to be considered when studying of cartridge valve flowcharacteristics. In this paper, the three-dimensional model of the integratedcartridge valve is established, consisting of the sleeve, the cone, the seat and theflow field. The liquid-solid-thermal coupling simulation is carried out. Thetemperature distribution of the solid and the flow field is showed. It is alsoobtained the deformation of the sleeve and the cone under the action of thethermal stress and fluid pressure. The conclusion is that the deformation of thesleeve and cone has influence on the clearance between them varied with thework condition. But the influence for the flow characteristics is negligible. Theliquid-solid-thermal coupling analysis for the whole valve has importantpractical significant. Finally, the test-bed for the flow characteristic and the dynamiccharacteristic of cartridge valve is built. To verify the formula of the crosssection area, the flow characteristics of valve at different opening anddifferential pressure is tested. Integrated into the formula of flow force and crosssection area, the AMEsim simulation model is established. The step response ofvalve is simulated. The step response of valve is tested at the different stepsignal valve. Comparing the simulation results to test results, it shows that thecomputational fluid dynamic formula provided by this paper provides the resultis credible.The above research results are to further improve the basic theory ofhydraulic valve. Formulas of cross section area and flow force are given even.The characteristic of valve can be studied even if cone moves at large stroke. Itsupplies theory basis for the non-linear modeling of hydraulic valve and hasengineering practical value.更多还原