The numerical study of nanoparticle deposition in a fully developed laminar flow under different conditions is presented. The diameter of the particles ranged from 20 nm to 200 nm and the density was 1060 kg/m3. The c...The numerical study of nanoparticle deposition in a fully developed laminar flow under different conditions is presented. The diameter of the particles ranged from 20 nm to 200 nm and the density was 1060 kg/m3. The calculated results show that the small particles deposit on the wall surface more easily. More large particles deposit on the bottom wall than on the upper wall. Under the laminar conditions, the number of particles that deposit is independent of the flow velocity. The smaller the flow region is, the more the particles deposit on the wall. The longer the particles remain in the flow, the more the particles deposit on the wall, and greater the difference between the number of particles depositing on the bottom wall and the upper wall.展开更多
针对同轴送粉的激光定向能量沉积(DED),结合送粉方程与VOF(Volume of Fluid)方法,提出了沉积层计算模型,采用固定坐标系下的移动边界条件,对单道IN718成形过程进行了实时模拟,并进行了实验验证。结果表明:在单层单道沉积加工下,随着扫...针对同轴送粉的激光定向能量沉积(DED),结合送粉方程与VOF(Volume of Fluid)方法,提出了沉积层计算模型,采用固定坐标系下的移动边界条件,对单道IN718成形过程进行了实时模拟,并进行了实验验证。结果表明:在单层单道沉积加工下,随着扫描速度从8 mm·s^(-1)增加到14 mm·s^(-1),沉积层高度和宽度分别减小了57.1%和21.6%,计算所得沉积层高度、宽度及熔深与实验结果吻合良好。在此基础上,计算了在单向平行搭接方式下搭接率为30%的单层双道沉积层温度场分布,得到了不同搭接时刻沉积层的温度变化规律。受第一沉积层热累积的影响,熔池潜热效应会使搭接加工时的表面最高温度略低于单道加工时的表面最高温度;同时受搭接沉积层在扫描过程中高温状态的影响,第一沉积层在搭接扫描过程中会出现回温现象,回温区间为1000~1600 K,幅度为100~300 K。该研究成果对深入理解同轴送粉激光定向能量沉积工艺机理以及工艺优化具有重要意义。展开更多
The YSZ coatings are prepared by the plasma spray-physical vapor deposition(PS-PVD)technology based on a specific experimental design.The structure,thickness and growth angle of YSZ coatings on the entire circumferent...The YSZ coatings are prepared by the plasma spray-physical vapor deposition(PS-PVD)technology based on a specific experimental design.The structure,thickness and growth angle of YSZ coatings on the entire circumferential surface of the cylindrical sample are studied.The results indicated that the structure,thickness and deflection growth angle of YSZ coatings are related to the orientation of deposition location.The numerical simulation of the multiphase mixed fluid near the substrate is carried out and the deposition regularity and mechanism of YSZ coatings prepared by PS-PVD is deduced.The growth rate is related to the local characteristics of the plasma flow field,and is directly proportional to the field pressure and inversely proportional to the field velocity.The growth angle of the coating is generally affected by the flow direction of the plasma jet.Especially,the normal component of velocity vector,V_(norm),mainly affects the speed at which the coating grows vertically upwards.The tangential component of velocity vector,V_(tan),determines the degree that the coating growth direction deviates from the vertical direction.When V_(tan)≠0,the coating forms a fine column with a certain deflection angle and finally develops into an oblique columnar structure.展开更多
基金Project supported by Major Program of the National Natural Science Foundation of China (Grant No: 10632070)
文摘The numerical study of nanoparticle deposition in a fully developed laminar flow under different conditions is presented. The diameter of the particles ranged from 20 nm to 200 nm and the density was 1060 kg/m3. The calculated results show that the small particles deposit on the wall surface more easily. More large particles deposit on the bottom wall than on the upper wall. Under the laminar conditions, the number of particles that deposit is independent of the flow velocity. The smaller the flow region is, the more the particles deposit on the wall. The longer the particles remain in the flow, the more the particles deposit on the wall, and greater the difference between the number of particles depositing on the bottom wall and the upper wall.
基金the financial support from National Natural Science Foundation of China(51771059)R&D Program in Key Fields of Guangdong Province of China(2019B010936001)+2 种基金National Science and Technology Major Project of China(2017-VI-0010-0081)Science and Technology Project of Guangdong Province of China(2017A070701027,2014B070705007)Sciences Project of Guangdong Academy of China(2019GDASYL-0104022)。
文摘The YSZ coatings are prepared by the plasma spray-physical vapor deposition(PS-PVD)technology based on a specific experimental design.The structure,thickness and growth angle of YSZ coatings on the entire circumferential surface of the cylindrical sample are studied.The results indicated that the structure,thickness and deflection growth angle of YSZ coatings are related to the orientation of deposition location.The numerical simulation of the multiphase mixed fluid near the substrate is carried out and the deposition regularity and mechanism of YSZ coatings prepared by PS-PVD is deduced.The growth rate is related to the local characteristics of the plasma flow field,and is directly proportional to the field pressure and inversely proportional to the field velocity.The growth angle of the coating is generally affected by the flow direction of the plasma jet.Especially,the normal component of velocity vector,V_(norm),mainly affects the speed at which the coating grows vertically upwards.The tangential component of velocity vector,V_(tan),determines the degree that the coating growth direction deviates from the vertical direction.When V_(tan)≠0,the coating forms a fine column with a certain deflection angle and finally develops into an oblique columnar structure.
