液压滑阀间隙热形变与污染颗粒分布的仿真研究

发布时间：2018-12-12 16:35

【摘要】：液压阀作为流体动力传动与控制的关键元件之一,被广泛应用于液压系统。然而,随着液压技术的全面发展,液压系统出现的故障失效问题越来越多,尤其是黏性耗散导致的滑阀热卡紧以及颗粒运动造成的滑阀污染卡紧等影响系统工作稳定性的问题也越来越受到重视。在中、高压系统中,液压滑阀常常出现的阀芯热卡紧现象,其主要原因是黏性油液流经滑阀阀口时,黏性加热效应使得局部区域温度升高、阀芯受热膨胀、配合间隙减小。与此同时,伴随着固体颗粒滞留于变形间隙内,污染卡紧进而产生,直接威胁液压系统的工作平顺性和安全性。本论文以典型阀口滑阀为研究对象,基于流固耦合共轭传热方法,运用COMSOL软件内置的共轭传热、固体力学、粒子追踪模块对液压滑阀内部的油液黏性加热、流动与传热、固体受热变形、颗粒运动等多个物理场之间的耦合过程进行了较为深入的分析。数值仿真结果表明:高温主要集中在速度梯度较大的区域以及受油液冲击的节流槽工作面,滑阀节流槽区域产生径向不均匀环状突起变形,阀芯、阀体配合边形成抛物线状径向热膨胀,固体颗粒在变形后的间隙均压槽内更易高度聚集,这些极有可能导致滑阀卡紧现象。本文的主要内容如下:第一章,阐述了本课题研究的背景和意义;介绍了滑阀液压卡紧与污染卡紧现象,对热力耦合形变和颗粒物污染导致滑阀阀芯卡滞故障的国内外相关研究的进展进行概述。第二章,简述COMSOL软件功能和应用场合,对所用计算模块的内置参数进行分析,叙述了滑阀内油液黏性温升的理论依据,根据阀口结构特点,参考等效过流面积的计算理论,推导了本文所研究的阀口等效过流面积计算公式,并对不同阀口形式下的阀腔内部流动与传热过程进行了数值解析。第三章,建立包含流体域和固体域耦合传热过程的单一数值计算模型,研究典型工况下滑阀全域的温度场分布与热变形规律,分析黏温特性、油液含气泡、热导率与温度的线性关系等现实因素对滑阀黏性温升形变的影响,依据已有仿真结果,改进阀芯次要结构,达到减小阀芯热变形量的目的。第四章,建立带有不同形式均压槽的二维滑阀全域热特性模型,探索不同工作压力、阀口开度、间隙大小等因素对滑阀配合间隙热特性的影响。第五章,建立带有不同均压槽形式的热变形前后间隙的二维对称模型,研究变形以后的滑阀径向配合间隙对滑阀内的颗粒物分布以及运动轨迹有何影响,综合考虑颗粒物滞留间隙与阀芯受热膨胀之间的联系,揭示两者对滑阀滞卡的综合作用机制。
[Abstract]:As one of the key components of fluid power transmission and control, hydraulic valve is widely used in hydraulic system. However, with the overall development of hydraulic technology, there are more and more failures in hydraulic system. Especially, the problems which affect the stability of the system, such as the thermal clamping caused by viscous dissipation and the slide-valve fouling due to particle movement, have been paid more and more attention. In the medium and high pressure system, the valve core heat clamping phenomenon often appears in the hydraulic slide valve, the main reason is that when the viscous oil flows through the valve mouth, the viscous heating effect causes the local temperature to rise, the valve core is heated to expand, and the matching clearance decreases. At the same time, with the solid particles stuck in the deformation clearance, the pollution jam is produced, which directly threatens the working comfort and safety of the hydraulic system. Based on the fluid-solid coupling conjugate heat transfer method, this paper uses the conjugate heat transfer, solid mechanics, particle tracing module built in COMSOL software to heat, flow and heat transfer the oil viscosity inside the hydraulic slide valve. The coupling processes of several physical fields, such as thermal deformation and particle motion, are analyzed in detail. The numerical simulation results show that the high temperature is mainly concentrated in the area with high velocity gradient and the working face of throttling groove which is impacted by oil, and the radial inhomogeneous annular bulge is produced in the throttle area of slide valve, and the valve core is produced. A parabolic radial thermal expansion is formed on the fitting edge of the valve body, and the solid particles tend to gather more easily in the clearance pressure slot after deformation, which may lead to the slide-valve clamping phenomenon. The main contents of this paper are as follows: the first chapter describes the background and significance of this research; This paper introduces the phenomenon of hydraulic clamping and pollution clamping of slide valve, and summarizes the progress of the research on sliding-valve spool sticking fault caused by thermo-mechanical coupling deformation and particulate contamination at home and abroad. In the second chapter, the function and application of COMSOL software are briefly described, the built-in parameters of the calculation module are analyzed, the theoretical basis of viscous temperature rise of oil in the slide valve is described, and the calculation theory of equivalent overflowing area is referred to according to the structural characteristics of the valve opening. In this paper, the equivalent over-flow area calculation formula of the valve is derived, and the flow and heat transfer process in the valve cavity under different valve orifices are analyzed numerically. In chapter 3, a single numerical calculation model of coupled heat transfer process in fluid domain and solid domain is established. The temperature field distribution and thermal deformation of the whole region of the sliding valve under typical conditions are studied, and the characteristics of viscosity and temperature are analyzed, and the bubbles in oil are analyzed. The effect of the linear relationship between thermal conductivity and temperature on the viscosity temperature rise and deformation of the slide valve is discussed. According to the existing simulation results, the secondary structure of the valve core is improved to reduce the thermal deformation of the valve core. In chapter 4, the global thermal characteristic model of two-dimensional slide valve with different pressure sharing groove is established to explore the influence of different working pressure, valve opening and clearance size on the thermal characteristics of sliding valve fit clearance. In the fifth chapter, a two-dimensional symmetrical model of the gap before and after thermal deformation with different pressure sharing groove is established to study the influence of radial fit clearance on particle distribution and motion trajectory in the sliding valve after deformation. Considering the relationship between the retention clearance of particulate matter and the thermal expansion of the valve core, the mechanism of their comprehensive action on the slide-valve lag card is revealed.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH137.52

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