基于分形特征的挖掘机多路阀配合面粗糙微结构的泄漏机理研究

In view of the internal leakage issue which exists prevalently in the multi-way valve, the flow characteristics in microchannel and heattransfer propertics are seen as the breakthrough to study the production mechanism of internal leakage in aim to reduce or even eliminate internal leakage. The project proceeds from the matching surface microcosmic appearance between the spool and valve bush, introduces fractal theory and creates precise 3d model of matching surface .Through improved micro-scale flow Micro-PIV measurement techniques, the molecular dynamics simulation and CFD and calculate the slip boundary condition are combined. The flow characteristics and heattransfer propertics of oil film between the clearance are researched, the model of internal leakage is creased, the optimization method of matching clearance structure is put forward. At last, a complete method of research about micro-scale flow between the spool and valve bush is formed. In addition, the results are tested and revised through experiments. Multi-way valve is the kernel component of hydraulic system in hydraulic excavator whose level of design and manufacture could directly affect the performance of hydraulic excavator. This project has practical significance for the internal leakage issue. Furthermore, it lays the theoretical foundation for the independent design of the high-performance hydraulic excavator in our country and promotes the development of our Micro-scale flow field.

针对当前液压挖掘机多路阀普遍存在的泄漏现象，以阀芯阀腔配合面间隙流动特性为突破口，研究泄漏产生的机理，从而减少甚至消除泄漏。本项目拟从多路阀阀芯阀腔配合间隙粗糙微结构表面微观轮廓着手，结合W-M函数和Monte Carlo方法建立配合面粗糙微结构的表面形貌模型；采用参变量变分原理和相应的有限元参数二次规划方法，通过改进的微尺度流动Micro-PIV测量技术，获得滑移边界条件；研究间隙内油膜的流动特性和传热特性，建立阀芯阀腔配合间隙泄漏模型，提出配合面粗糙微结构的优化方法，寻求配合面粗糙微结构表面形貌与多路阀泄漏、磨损之间的关联性，并通过实验对结果进行验证。多路阀是液压挖掘机液压系统中的核心部件，其设计制造水平直接影响液压挖掘机的整机性能。本项目的研究成果为保证应用于挖掘机上的多路阀执行其合流、再生、优先、流量控制等复杂功能的稳定性和可靠性，形成我国自主的高性能多路阀设计方法奠定理论基础。

本项目以提高多路阀的控制特性及可靠性为目标，重点考虑了对中弹簧刚度、阀口死区、流量系数和油缸摩擦等非线性因素，旨在有效提高工程机械液压系统的操控性、可靠性等，为我国工程机械更新换代提供技术支撑。首先建立了W-M函数表征的用尺寸独立性分形参数描述的阀芯与阀腔配合表面的形貌，通过计算流体力学方法对缝隙中油膜的流动特性进行了分析，对比分析了壁面滑移、温黏特性、阀芯偏心及几何加工误差对间隙流动的影响。其次采用多目标密切值优化方法研究出了不同结构及不同配置方式的均压槽对减小内泄漏和径向力的效果影响，得到使泄漏总功率损失最小时的缝隙结构，优化了平衡槽的参数。然后设计了双阀芯实验用模型，建立了其电液比例系统数学模型及平衡槽优化前后的实验平台，对工作装置压力、位移等特性进行了分析研究。最终预测了阀芯与阀腔配合表面缝隙的泄漏率，对比分析搭建了长阀芯实验平台和短双阀芯平台，研究发现双阀芯系统的压力响应较快，功率消耗小，超调量较小，提高了阀的控制特性和可靠性并优化了系统性能。