【作者】 张宏；

【导师】 熊诗波；

【作者基本信息】 太原理工大学 ， 机械电子工程， 2008， 博士

【摘要】 采煤工作面用的液压支架是一种复杂的煤矿机械,它能够可靠有效地支撑和控制工作面的顶板,保证工人安全和各种作业的正常进行。电液控制液压支架是当前先进采煤技术装备的重要标志之一,而高压高水基电磁先导阀是电液控制系统的核心元件,其结构复杂、精密度高,目前世界上只有德国和美国等少数国家研究和生产制造,属高难技术。我国曾尝试过自行设计、制造这种液压阀,但由于没有运用多学科理论和现代数字技术等手段去深入研究液压阀的关键技术问题,只是凭借经验和已有的资料进行设计,致使研制失败。因此,目前我国高压高水基电磁先导阀仍然依靠进口,成为制约我国采煤技术由机械化向自动化发展的关键技术之一。本论文首先研究高压高水基液压阀的冲蚀磨损与密封泄漏机理等关键技术问题。然后,将该成果应用于液压支架电磁先导阀的理论分析和结构设计中,使基础研究与实际应用相结合,为成功开发高水基电磁先导阀提供理论支持。作者以计算流体力学(CFD)理论、分形(FRACTAL)理论与多刚体系统动力学理论等为依托,采用理论、仿真、试验相结合的方法,建立液压阀流场仿真模型、泄漏机理模型、动力学仿真模型和系统仿真模型,并进行数值计算分析,为此类液压阀的设计提供可靠的理论依据。高水基液压阀流动过程的壁面磨损行为,严重影响液压阀的使用寿命。作者综合应用计算流体动力学(CFD)理论与冲蚀(EROSION)理论的分析方法,研究高速高压条件下液压阀的冲蚀磨损机理,建立高水基液压阀流体湍流和冲蚀的数学模型。通过可视化模拟,预测了煤粒对高水基平面阀和球阀不同部位的冲蚀磨损分布,比较准确地确定了冲蚀磨损对关键元件的影响区位和程度。研究阀芯和顶杆间的微动磨损与冲蚀的交互破坏,指出了采用侧顶杆结构可以避免磨损叠加。另外,作者对几种非金属材料的冲蚀磨损特性进行实验研究,为高水基液压阀密封副材料的优选提供了依据。作者使用现代数字技术,开展高水基介质液压阀气蚀(CAVITATION)问题的研究,以解决这个难于用实验方法研究的问题。通过高水基液压阀流体气蚀的数学模型,研究高水基液压阀低压密封的汽穴形成,找出最易产生气穴与气蚀现象的位置。分析表明,低压区对应气体体积百分比高的气穴区域,侧顶杆结构同样可以减轻液压阀的气蚀磨损。分形(FRACTAL)几何学的建立,为研究复杂无规律的现象提供了新的理论与方法。在考虑端面形貌变化的基础上,作者提出了基于分形理论研究高水基液压阀的微观密封机理的思路。分析了密封副端面粗糙轮廓波谷面积和弹性接触点面积的微观接触机理及相互关系。以缝隙流动的N-S方程为基础,推导出泄漏量与表面粗糙度、分形参数、密封接触比压之间的关系及相应的计算公式,建立了泄漏量分形模型。通过数值仿真,讨论了分形参数、密封力与泄漏量间的相互关系,结果表明,控制表面形貌参数可以有效降低液压阀泄漏量。另外,作者对泄漏量与不同的表面粗糙度、密封比压、密封面宽度之间的关系进行了试验研究,得出了具有工程应用指导意义的定量结论。针对电液控制支架的特殊要求,作者设计了先导阀的螺线管结构电磁铁。模拟了磁感应强度的大小及其在空间的磁场分布情况,并对电磁铁的关键结构参数进行优化,保证该电磁铁响应速度快,动作平稳可靠。通过可视化模拟和分析得知,磁通密度最高的地方是衔铁与极靴导套端重叠部分,极靴内径单侧间隙的变化对吸力起决定作用。最后,对电磁铁的吸力特性进行试验,验证了数值分析的正确性。在研究电磁先导阀的运动特性时,虚拟样机技术有助于做出前瞻性的决策。为了评定先导阀动态特性,作者引入位移响应曲线来衡量其动态性能。通过求解先导阀的动态数学模型,获得反映动态特性的数值计算结果。综合考虑先导阀内部运动元件的接触碰撞及运动拓扑关系,建立先导阀详细的三维实体模型。研究阻尼系数、质量和刚度变化对先导阀动力学特性的影响,准确地预知其在实际工况下的动态性能。根据预定的系统性能和预期的目标反复修正几何参数,最终达到预期的动态响应性能,为先导阀的设计开辟了一条新的思路。电磁先导阀工作口压力的变化,会引起其内部流场相应变化,而先导阀出口压力又受到液控主阀、立柱等负载的影响。因此,作者从系统角度对先导阀的动态响应进行研究,建立了基于AMESim的支架电液控制系统的仿真模型,得到先导阀工作口的不同压力、流量响应曲线,为先导阀流场仿真的初始边界条件的设定提供依据。在此基础上,研究先导阀的流场分布。根据先导阀的压力损失、速度分布等随流量、出口压力和入口位置的变化关系,确定高水基电磁先导阀的最佳合理结构。本文的研究工作涉及多学科理论和现代试验技术,主导思想是在创新体系下进行多种学科的交叉与融合,以此途径对高压高水基液压阀的理论问题及设计方法进行研究,从而解决实际问题。更多还原

【Abstract】 The powered support of fully mechanized coal face is a kind of complicated coal mine machinery, which can sustain and control the roof of working face reliably and efficiently, guaranteeing coal miner’s safety and the operation of normal tasks. The electro-hydraulic controlled powered support is one of the important signs in the currently advanced excavate coal equipment. High pressure and high water-based (HPHWB) solenoid pilot valve is the key component of the electro-hydraulic control system which has complex structure and high precision. At present it was researched and manufactured only in some countries like Germany and America. It belongs to a difficult technology. Our country ever made an attempt to design and manufacture the hydraulic valve independently, but failed, because it needs further research on the key technology of HPHWB hydraulic valve based on the synthesis means of multidiscipline theory and modern digital technique, except the experience and old data. Thereby, HPHWB solenoid pilot valve still depends on import in our country, which becomes one of the pivotal technologies that restrict domestic development in coal mining technique from mechanization to automation.The thesis first discusses the key technology problem of erosion wear and sealing leakage mechanism for HPHWB hydraulic valve; then applies the result-to the theory analysis and structural design of solenoid pilot valve, thus combining the basic research with practical application and offering a theoretical support for development pilot valve. Based on computational fluid dynamics (CFD), fractal theory and multi-rigid-body system dynamics theory and so on, the author establish flow field simulation model, leakage mechanism model, dynamics simulation model and system simulation model of hydraulic valve by combining means of theory, simulation and examination, and then make analysis of numerical calculation. Credible theory basis is offered for the hydraulic valve design.Wall faces abrasion of HPHWB hydraulic valve affect strongly the operation life of hydraulic valve. The author researches erosion wear mechanism of hydraulic valve under the high velocity and high pressure condition by combining technology of CFD and erosion theory, and establishes erosive mathematical model of HPHWB hydraulic valve. By visual simulation, erosion wear distribution of coal particles eroding plain valve and ball valve are predicted; accurately indicate the influencing position and degree of key components eroded. Moreover, the author research interactive breakage of fretting wear and erosion wear between valve core and pole. A means for avoiding wear superposition is suggested by changing the center pole structure to sidepiece pole structure. In addition, the author makes experimental investigation to several kind nonmetals, and offer basis for optimum seeking of sealing material of HPHWB hydraulic valve.Using modern digital technique, the author carries on cavitation study of high water-based medium hydraulic valve to solve the problem difficult to research by experiment. By using cavitation mathematical model of high water-based hydraulic valve, cavitation form of low pressure sealing will be researched, and the positions that produce cavitations will be easily found. Analyses show that low-pressure zone corresponds with the cavitation zone of high vapor volume fraction, and sidepiece pole structure can likewise reduce cavitation.The foundation of fractal geometric provides new theory and means for the research on complex and ruleless phenomenon. On the basis of surface appearance changing, the author puts forward train of thoughts of microscopic seal mechanism for HPHWB hydraulic valve, and analyzes microscopic contact mechanism of wave trough and elastic point contact area of rough surface. Then the author derive the calculating formulas of leakage rate and surface roughness, fractal parameter, sealing contact pressure based on aperture current N-S equation, establishes leakage model of fractal parameters, and discuss the relations of fractal parameter, seal force and leakage rate by numerical simulation. Results show controlling surface appearance parameters are able to availably reduce leakage rate of hydraulic valve. Besides, after experiment studying the relation of leakage rate between different surface roughness, seal contact pressure, and the seal width, the author comes to the quantitative conclusion that is meaningful to engineering application.As to peculiar request of the electro-hydraulic controlled powered support, the author uses the solenoid structure design electromagnet that adapt to pilot valve in the powered support. Flux density and flux lines contour are simulated, and the key structure parameters of electromagnet are optimized to make sure that the electromagnet response speed is rapid and operating smooth is reliable. Results show that the highest place of flux density is superposition of armature and guide sleeve end of pole piece, and the changing for pole piece inside diameter unilateral gap settle on the thrust characteristic. Finally, experiment confirms the validity of numerical analysis.When the movement property of solenoid pilot valve is studied, virtual prototype technology contributes to a forward-looking decision. In order to evaluate dynamic characteristics of pilot valve, the author introduced displacement response curve to measure its dynamic performance. Numerical computational results are obtained by solving the dynamic mathematic model of pilot valve. The author make three-dimensional solid model based on considering synthetically contact and topological relation of pilot valve interior movement components, and study the changes of damping coefficient, mass and stiffness to dynamic characteristics effect of pilot valve, predict accurately its dynamic performance under the real operating condition. Geometric parameters are repeatedly modified in accordance with preconcerted system performance and prospective target; finally achieve perfect dynamic response performance. A new thought is opened up for pilot valve design.Pressure change in the operating orifice of solenoid pilot valve will cause its internal change in flow field, while outlet pressure change of pilot valve is affected by hydraulic-controlled main valve and leg and so on. Therefore, the author conduct a research on dynamic response of pilot valve from view of system, establishes simulation model of electro-hydraulic controlled system based on AMESim, and obtain different flow-pressure characteristic curve of operating orifice of pilot valve, and then offer basis for initial boundary set of flow field simulation of pilot valve. Flow field distribution of pilot valve are studied on the basis of the above conclusion; and reasonable structure of HPHWB pilot valve is established according to varying relations that pressure loss and velocity distribution change with flow rate, outlet pressure and inlet position of pilot valve.Studies program of the paper involved multidisciplines theory and modern experiment technology, which predominant idea is overlapping and fusion of multidisciplines under innovative system. Based on the approach, the author research on theory problem and design method of high pressure and high water-based hydraulic valve, and resolve the practical problem.更多还原