前混合磨料射流清洗喷嘴内外流场的仿真研究

发布时间：2018-11-20 15:03

【摘要】：前混合磨料射流清洗技术是上世纪80年代兴起的一项技术。其工作过程如下:首先磨料和水通过磨料罐提前混合,形成的磨料浆体在一定长度的耐高压的钢丝编织软管中再次混合并加速,然后通过喷嘴形成高速射流,射流接触到被清洗靶物,最终达到清洗的目的。在这个过程中,由于磨料经过多次加速,因此射流具有较高的能量,这也是为什么前混合磨料射流可以在较低的压力下进行清洗和切割工作。虽然磨料射流具有很多优势,但我国在高压水射流清洗技术方面还存在一些问题,其中包括喷嘴的选型、参数的选择不够恰当,这将会导致清洗设备的效率低下,使得磨料射流不能完全发挥自身优势,因此喷嘴可以说是整个设备的核心部件。在探究喷嘴的结构参数对射流的影响时,由于磨料和水混合属于固液两相流,仅仅靠理论分析是不行的,而通过实验观察也很难得到理想的结果。本文将采用数值仿真的方法,对前混合磨料射流喷嘴内外流场进行分析。为了探究喷嘴不同的结构参数对喷嘴内外流场的影响规律,文章通过Gambit、Fluent、Origin三种软件,实现对喷嘴的结构建模、数值模拟分析及数据后处理。根据数据处理结果,可以总结出喷嘴的不同结构参数(圆柱段长度、收缩角、圆弧段长度)对射流速度的影响规律,得出流线型喷嘴较为适宜用于清洗工作,最后针对清洗用流线型喷嘴,通过改变喷嘴圆柱段长度、圆弧段长度和收缩角等参数,分析比较不同的圆柱段长度、圆弧段长度和收缩角参数对喷嘴的内外部流场的影响,另外分析了磨料浓度对射流性能的影响,得出入口直径为6mm、出口直径为1mm、圆柱段长度为6mm、圆弧段长度为8mm、收缩角为17°的流线型喷嘴在磨料浓度介于20%和30%之间时较适宜清洗工作。本文在进行数值模拟及参数优化时,不仅考虑水和砂的轴心速度分布及衰减程度,还分析了水和砂在不同射流截面上的速度分布。探究不同结构参数对射流性能的影响规律,探索更加适宜清洗工作的喷嘴类型,为设计出结构优良、高效率的水射流喷嘴提供理论依据。
[Abstract]:Pre-mixed abrasive jet cleaning technology is a rising technology in 1980's. The working process is as follows: firstly, the abrasive slurry is mixed and accelerated in a steel wire braided hose with a certain length of high pressure resistance by mixing the abrasive and water in advance through the abrasive tank, and then a high-speed jet is formed through the nozzle. The jet reaches the target to be cleaned, and finally achieves the purpose of cleaning. In this process, the jet has higher energy due to the abrasive acceleration, which is why the pre-mixed abrasive jet can be cleaned and cut at lower pressure. Although abrasive jet has many advantages, there are still some problems in high pressure water jet cleaning technology in our country, including the selection of nozzle and the inadequate selection of parameters, which will lead to the low efficiency of cleaning equipment. The abrasive jet can not give full play to its own advantages, so the nozzle can be said to be the core part of the whole equipment. In order to investigate the influence of nozzle structure parameters on jet flow, because the mixture of abrasive and water belongs to solid-liquid two-phase flow, it is not possible to rely on theoretical analysis alone, and it is difficult to obtain ideal results through experimental observation. In this paper, numerical simulation method is used to analyze the internal and external flow field of the pre-mixed abrasive jet nozzle. In order to investigate the influence of nozzle structure parameters on the flow field inside and outside the nozzle, the structure modeling, numerical simulation and data post-processing are realized by Gambit,Fluent,Origin software. According to the data processing results, the influence of different structure parameters (cylinder length, shrinkage angle, arc length) on jet velocity can be summarized, and it is concluded that streamline nozzle is more suitable for cleaning. Finally, aiming at the streamline nozzle for cleaning, by changing the parameters such as cylinder length, arc length and shrinkage angle, the effects of different cylinder length, arc length and shrinkage angle on the internal and external flow field of the nozzle are analyzed and compared. In addition, the influence of abrasive concentration on jet performance is analyzed. The results show that the diameter of inlet and outlet is 6mm, the diameter of outlet is 1mm, the length of cylinder is 6mm, and the length of arc is 8mm. The streamline nozzle with shrinkage angle of 17 掳is suitable for cleaning when the abrasive concentration is between 20% and 30%. In numerical simulation and parameter optimization, not only the axial velocity distribution and attenuation degree of water and sand are considered, but also the velocity distributions of water and sand in different jet sections are analyzed. The influence of different structure parameters on jet performance and the type of nozzle which is more suitable for cleaning are explored, which provides a theoretical basis for the design of water jet nozzle with excellent structure and high efficiency.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG664

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