液压油箱中固体颗粒运动轨迹及分布的仿真研究

发布时间：2018-06-07 06:19

本文选题：液压油箱 + 欧拉-格朗日模型　；参考：《兰州理工大学》2017年硕士论文

【摘要】：颗粒物污染亦是液压油的主要污染物之一。液压油箱的的主要功能是存储流体和补充液压系统操作过程中所有的体积变化,除此之外液压油箱提供了各种有利于系统和各类元件的其他功能,其中,最为重要的是确保液压组件在正常操作下油液中空气的分离及固体颗粒污染物的沉淀,颗粒物作为液压油箱中的污染物之一随油液由泵吸入进入液压系统,由于颗粒污染加速液压元件的磨损、导致液压阀的卡滞及系统故障,所以对于设计具有较高颗粒沉降速率的新型液压油箱对液压系统的整体性能及液压组件的寿命至关重要。本论文通过数值模拟计算,分析获得油箱中油液的流动状态和固体颗粒运动轨迹的分布,为新型液压油箱的设计提供研究依据。研究结果表明:油箱中的某些循环区域会形成高湍流强度区域,显著影响颗粒的运动。粒径大的颗粒运动受到湍流的影响较小,粒径小的颗粒运动易受到湍流影响;粒径小的颗粒与流体之间有较好的跟随性;颗粒运动过程中受到湍流的影响随液流速度的增加而增强;另外,通过对比分析不同结构油箱中颗粒的沉降特点,在油箱中设置隔板和扩散器能延长油液的流动路径、稳定液流进入油箱的状态、增加颗粒的停留时间,提高固体颗粒的去除率。为新型液压油箱的设计提供依据。第一章,通过液压油箱的概述阐述了固液两相流仿真技术在液压系统中的应用;概述了关于液压油箱各方面性能提高的国内外研究现状及主要存在的问题;对本论文的研究做了概括和总结。第二章,对油箱中颗粒运动所受力进行理论分析,建立液压油箱的CFD计算模型,运用CFX软件中的欧拉-拉格朗日模型对液压油箱内固-液两相流流场进行数值模拟,研究分析不同粒径下颗粒的运动轨迹以及油液的流动对颗粒运动的影响,提出了提高颗粒沉降的方法。第三章,结合上章计算结果的分析和设想,提出并建立了几种不同结构的油箱模型,根据油液的流动状态和颗粒物沉积的特点及运动轨迹,改变油箱的结构,分析结构改进后的流场分布,同时对固体颗粒分布进行模拟,设计出具有较高颗粒沉降速率的新型液压油箱。第四章,利用CFX软件中的欧拉-欧拉模型,计算固体颗粒物在液压油箱中的体积分数;分析不同模型中颗粒最终的集聚位置;并对不同油箱模型出口处颗粒的体积分数进行计算,从而对比说明不同结构中颗粒的沉降性能。本文基于理论分析和CFX数值仿真等手段,研究分析不同粒径颗粒污染物在油箱的运动轨迹,获得颗粒在油箱中运动的物理机制,从而以此为出发点,提出了几种不同的提高颗粒物沉降的结构,研究结果对于提高液压油箱中颗粒污染物的沉降率有一定的指导意义,而且为新型液压油箱的设计提供依据。
[Abstract]:Particulate matter pollution is also one of the main pollutants in hydraulic oil. The main function of the hydraulic oil tank is to store the fluid and replenish all the volume changes during the operation of the hydraulic system. In addition, the hydraulic oil tank provides a variety of other functions in favor of the system and various components, among which, The most important thing is to ensure the separation of air in the oil and the precipitation of the contaminants from the solid particles under normal operation of the hydraulic components. The particles, as one of the pollutants in the hydraulic tank, enter the hydraulic system with the suction of the oil through the pump. Particle pollution accelerates the wear of hydraulic components, which leads to the stagnation of hydraulic valves and system failure, so it is very important to design a new type of hydraulic oil tank with high particle settling rate for the whole performance of hydraulic system and the life of hydraulic components. In this paper, the flow state of the oil in the tank and the distribution of the motion trajectory of the solid particles are obtained by numerical simulation, which provides the basis for the design of the new type of hydraulic oil tank. The results show that some circulating regions in the tank will form a high turbulence intensity region, which has a significant effect on the movement of particles. The movement of particles with large particle size is less affected by turbulence, the movement of particles with small particle size is easily affected by turbulence, and the movement of particles with small particle size is better followed by fluid. The effect of turbulence on particle motion increases with the increase of liquid flow velocity. In addition, by comparing and analyzing the settling characteristics of particles in different oil tanks, the flow path of oil can be prolonged by setting separators and diffusers in the tank. Stable liquid flow into the tank state, increase the residence time of particles, improve the removal rate of solid particles. It provides the basis for the design of the new type hydraulic oil tank. In the first chapter, the application of solid-liquid two-phase flow simulation technology in hydraulic system is described through the overview of hydraulic tank, and the domestic and international research status and main existing problems of improving the performance of hydraulic tank in various aspects are summarized. The research of this paper is summarized and summarized. In the second chapter, the theoretical analysis of the force acting on the particles in the tank is carried out, and the CFD calculation model of the hydraulic tank is established, and the numerical simulation of the solid-liquid two-phase flow field in the hydraulic tank is carried out by using the Euler-Lagrange model in the CFX software. The effect of particle trajectory and oil flow on particle movement was studied and the method of increasing particle sedimentation was put forward. In the third chapter, combined with the analysis and assumption of the calculation results in the previous chapter, several oil tank models with different structures are put forward and established. According to the flow state of the oil and the characteristics and track of the particles deposition, the structure of the oil tank is changed. The flow field distribution of the improved structure is analyzed and the distribution of solid particles is simulated. A new type of hydraulic oil tank with high settling rate of particles is designed. In chapter 4, the volume fraction of solid particles in hydraulic tank is calculated by using Euler-Euler model in CFX software, and the final accumulation position of particles in different models is analyzed. The volume fraction of particles at the outlet of different fuel tank models is calculated, and the settling performance of particles in different structures is compared. Based on the theoretical analysis and CFX numerical simulation, this paper studies and analyzes the movement trajectory of different particle size pollutants in the tank, and obtains the physical mechanism of the particle movement in the tank, thus taking this as the starting point. Several different structures for increasing particle deposition are proposed. The results have certain guiding significance for improving the settling rate of particulate pollutants in hydraulic oil tanks and provide the basis for the design of new type hydraulic oil tanks.
【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】：TH137.5

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