插装型锥阀配合副流固热耦合分析及流场可视化

发布时间：2018-08-14 15:30

【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。
[Abstract]:With the rapid development of hydraulic technology, the hydraulic system is required to meet the requirements of high pressure, large flow, but small size, light weight, high precision and high efficiency. The technology of hydraulic cartridge valve came into being under this situation. The emergence of two-way cartridge valve has raised the development of hydraulic technology to a new stage. In some applications, cartridge valves are the only option to increase productivity and competitiveness.
The scientific problems related to hydraulic valves, the flow characteristics of various types of hydraulic valves, the magnitude and direction of hydrodynamic forces acting on the spool, the effects of hydrodynamic forces on the operational reliability, operational flexibility, dynamic and static characteristics of the valve, and the visualization calculation of internal flow field have been the basic research issues and development in the field of fluid transmission and control technology. The key problem of high performance hydraulic control valve must be solved. As the main structure form of cartridge valve, cone valve has been found that the existing theory needs to be further studied and solved.
The cross-section area of valve orifice has a direct influence on the calculation of valve flow characteristics, but there are still some problems in the existing theory about the calculation formula of cone valve cross-section. Based on the definition of cross section, the flow field of cone valve is studied and analyzed by CFD visualization technology, and the position of cross section with different openings in the whole large stroke range is found. If the spool stroke is large, the traditional formula is no longer applicable, and the flow characteristics are very different under different flow conditions. Firstly, the critical opening of the traditional formula is established, and the formula for calculating the cross-section area of the flow passage under different flow conditions is deduced. Cavitation resistance is also an important indicator of throttling performance, but the criteria for judging cavitation initiation are not yet unified.
Hydraulic power has a great influence on the dynamic and static characteristics of the valve and is an important factor to be considered in the design of hydraulic valves.The hydraulic power calculation formula is one of the important basic equations for modeling the characteristics of hydraulic systems and has a great influence on the characteristics of hydraulic systems. The traditional theoretical formula is no longer applicable to the calculation of its hydrodynamic force. The hydrodynamic force is essentially caused by the change of the pressure distribution on the wall of the valve spool caused by the fluid movement. Therefore, starting from the analysis of the flow field, the value of pressure distribution at the bottom of the valve spool can be obtained, and the value of hydrodynamic force can be obtained by integrating the pressure relative action area. In order to facilitate the practical use of engineering, according to the main factors of hydrodynamic force produced by the analysis of flow field and the selection principle of control volume, different control volumes are selected for cone valves with different valve ports under different internal and external flow conditions. The corresponding formulas are used to calculate the hydrodynamic characteristics of the valve orifice in different flow directions with higher accuracy.
In the traditional hydrodynamic calculation formula, the hydrodynamic force is directly proportional to the difference of inlet and outlet pressure, and has nothing to do with the value of inlet and outlet pressure.But when the inlet and outlet pressure is the same, the flow state in the valve becomes two-phase flow when the inlet and outlet pressure is low, which is different from the flow characteristics of single-phase flow, so the traditional formula needs to be revised. Value and critical outlet pressure are used to distinguish the different flow characteristics in the valve.The two-phase flow field in the valve is simulated by using the full-cavity model.The pressure distribution in the valve is analyzed.The real reason for the difference of hydrodynamic force under the same inlet and outlet pressure difference and different inlet and outlet pressure value is clarified.The traditional formula is revised and its application is deduced. The calculation formula of hydrodynamic force in two-phase flow is verified by the existing experimental data.
Hydraulic technology spreads all over the industrial control field, including some high-tech fields. In order to achieve more precise control, the characteristics of control components will be more demanding. Therefore, in the study of cartridge valve flow characteristics, considering the influence of valve sleeve and spool deformation on throttle flow area and valve sleeve spool clearance, it will be hydraulic. It is necessary to perfect the theory of component design. A three-dimensional model of cartridge valve is established, including the valve body sleeve. The liquid-solid-heat coupling analysis of the cartridge valve is carried out. Firstly, according to the heat transfer characteristics of the fluid flow process of the hydraulic valve, the flow field and temperature field of the fluid flow process are numerically simulated, and the solid and liquid of the whole cone valve are obtained. The analysis shows that the deformation of the spool sleeve has a certain influence on the fit clearance of the spool sleeve, but the two effects will vary greatly according to the different working conditions of the cone valve and should be aimed at in the actual process. The influence of the deformation of the spool sleeve on the throttling characteristics of the cone valve can be neglected. To a certain extent, the influence of the deformation on the fit clearance and the valve port characteristics of the spool sleeve can be scientifically estimated by the Fluid-Solid-Heat coupling analysis of the whole valve, thus providing a reference basis for the spool design of the valve sleeve.
Finally, a test bench for measuring the flow characteristics and dynamic characteristics of cartridge valves is built to test the flow characteristics of the valves under steady flow with different pressure differences and different openings. The model parameters are set up to simulate the step response of the valve, and the step response of the valve is tested with different step signals given. The results of the simulation and test of the step response are compared. The results show that the calculation results obtained by the hydrodynamic formula are reliable.
The above research results have further improved the basic theory of hydraulic valve hydrodynamics, given the calculation formula which can accurately describe the hydrodynamic force acting on the valve core of conical cartridge type main valve in the large stroke range, the calculation formula of the cross-section area of conical valve flow, and carried on the nonlinear digital imitation for establishing the accurate mathematical model of hydraulic valve from the mechanism. Real research provides a theoretical basis and has certain engineering practical value.
【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH137.52

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