约束喷射沉积过程数值模拟及实验研究

发布时间：2018-05-01 05:21

本文选题：喷射沉积连续挤压 + 雾化器　；参考：《昆明理工大学》2017年硕士论文

【摘要】：喷射沉积连续挤压是新近提出的一种利用快速凝固技术制备高合金材料的近净成形新技术,该技术有效的融合了喷射沉积技术和连续挤压技术的优点,具有广阔的应用前景。喷射成形过程和连续挤压过程都很复杂,需控制的工艺参数众多。本文采用双旋转盘流型控制器约束雾化射流,对雾化过程进行数值模拟,并参照试验结果进行了全面的阐述和分析,揭示不同工艺参数对雾化过程的影响,为高合金材料的生产奠定基础。采用计算流体力学软件Fluent提供的RNGκ-ε湍流模型、TAB(泰勒比)模型以及DPM离散模型对环孔型和环缝型雾化器气体流场进行分析,结果表明其他参数相同的情况下,环孔型雾化器压力区域为半封闭状,雾化器导流管内部熔体压强较小,气孔中心的速度值较大,对液柱的冲击破碎能力更强,较适合于喷射沉积连续挤压技术。对比五种不同出气口交角的自由式雾化器气体流场,为增加雾化效果,减小涡流区的影响,降低导流管内部熔体的压力,雾化器出气口夹角最佳参数为25°。对比传统自由与约束喷射沉积的雾化流场,发现流场中的熔滴在双旋转盘流型控制器的约束作用下,熔滴以扇形扩散且偏向一侧,与实验结果一致,而且整个过程中速度没有很大的衰减。气体压力为0.25MPa时,沉积坯没有明显的氧化现象,且沉积坯能与连续挤压机轮槽恰好匹配。对熔滴在流场中变形破碎的数值模拟结果,发现熔滴前后端驻点静压力场和速度分布不均匀,且相对速度越大,熔滴表面的静压力分布越不均匀,熔滴越容易发生变形破碎。对熔滴在三种倾斜角度的壁面铺展过程模拟研究,发现随着壁面倾斜角度从0°增大到60°,熔滴沿壁面向前铺展的速度较快,向后的铺展速度减小到0,熔滴与壁面的接触面积增加,形成卷入式气孔的可能性减小,且液态金属层预先凝固边缘不易向内卷曲收缩,铺展更均匀,与实验结果基本一致。
[Abstract]:Spray deposition continuous extrusion is a new near net forming technology for preparing high alloy materials using rapid solidification technology. This technology effectively combines the advantages of spray deposition technology and continuous extrusion technology and has a broad application prospect. The spray forming process and the continuous extrusion process are very complex, and many technological parameters need to be controlled. In this paper, the atomization process is numerically simulated by using a double rotating disk flow pattern controller to constrain the atomization jet, and the influence of different process parameters on the atomization process is revealed by a comprehensive description and analysis with reference to the experimental results. Lay the foundation for the production of high alloy materials. The gas flow field of annular and annular atomizer is analyzed by using RNG 魏-蔚 turbulence model and DPM discrete model provided by computational fluid dynamics software Fluent. The results show that the other parameters are the same. The pressure region of annular nebulizer is semi-closed, the melt pressure in the tube of atomizer is small, the velocity value of pore center is larger, and the impact crushing ability of liquid column is stronger, which is more suitable for the continuous extrusion technology of spray deposition. In order to increase the atomization effect, reduce the influence of eddy current zone and reduce the pressure of melt in the tube, the optimum parameter of the air outlet angle of the atomizer is 25 掳, in order to increase the atomization effect and reduce the pressure of melt in the tube, the gas flow field of the free atomizer with five different exit angles is compared. Compared with the atomization flow field of conventional free and confined spray deposition, it is found that the droplet diffuses in a fan shape and deviates to one side, which is consistent with the experimental results, and the droplet in the flow field is confined by a double-rotating disk flow pattern controller. And there is no great attenuation in the speed of the whole process. When the gas pressure is 0.25MPa, there is no obvious oxidation phenomenon in the deposited billet, and the billet can exactly match the wheel groove of the continuous extruder. The numerical simulation results show that the static pressure field and velocity distribution are not uniform at the end of the droplet, and the larger the relative velocity, the more uneven the static pressure distribution on the surface of the droplet is, and the easier the droplet is to be deformed and broken. The simulation study on the spreading process of the droplet on the wall of three inclined angles shows that with the increase of the sloping angle of the wall from 0 掳to 60 掳, the velocity of the droplet spreading along the wall is faster, the backward spreading speed decreases to 0, and the contact area between the droplet and the wall increases. The possibility of forming the entrapped pores is reduced and the solidification edge of the liquid metal layer is not easy to curl and shrink inwards and spread out more evenly which is basically consistent with the experimental results.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG376

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