| 引用本文: | 张云鹏,李海涛,鲍思洁,郭冬妮,万冰华,卢文壮.喷涂参数对螺栓表面涂层均匀性的影响[J].中国表面工程,2024,37(5):263~274 |
| ZHANG Yunpeng,LI Haitao,BAO Sijie,GUO Dongni,WAN Binghua,LU Wenzhuang.Influence of Spraying Parameters on the Uniformity of Bolt Surface Coating[J].China Surface Engineering,2024,37(5):263~274 |
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| 摘要: |
| 工程中螺栓喷涂铝涂层时易出现涂层厚度不均匀，会导致螺栓连接的可靠性下降和涂层电偶腐蚀防护作用削弱问题， 航空钛合金螺栓表面铝涂层均匀性方面缺乏深入的研究。采用欧拉-拉格朗日法建立雾化流场的气液两相流物理模型，分析喷涂距离、进气压力和扇面控制压力对螺栓表面涂层厚度的影响，并搭建喷涂试验系统与模拟结果进行比对。结果表明：喷涂距离大小会影响涂料液滴到达螺栓表面时的速度，进而影响涂层厚度和均匀性。进气压力较小时，涂料雾化不彻底，涂层出现不均匀的斑块；进气压力较大时，涂覆的范围较大，单个螺栓表面涂层过薄。扇面控制压力较小时，喷雾集中，螺栓表面涂层较厚；扇面控制压力则会影响喷雾范围，若喷雾集中，螺栓表面涂层较厚，反之螺栓表面涂层较薄。当喷涂距离在 190 mm 左右，进气压力在 0.4 MPa 左右，扇面控制压力在 0.1 MPa 左右时，螺栓表面涂层厚度均匀性最佳。试验证实气液两相流物理模型用于研究喷雾流场和预测涂层厚度分布是可行的。采用欧拉-拉格朗日法模拟螺栓表面喷涂成膜的过程，获得涂层厚度分布规律，能为航空钛合金螺栓表面铝涂层均匀制备提供可行的方法。 |
| 关键词: 喷雾流场 铝涂层 计算流体力学仿真 涂层均匀性 |
| DOI：10.11933/j.issn.1007-9289.20230923001 |
| 分类号:TH162 |
| 基金项目:天津市紧固连接技术企业重点实验室项目（TKLF2022-01-B-04） |
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| Influence of Spraying Parameters on the Uniformity of Bolt Surface Coating |
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ZHANG Yunpeng1，LI Haitao2，BAO Sijie1，GUO Dongni2，WAN Binghua3，4，LU Wenzhuang1
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1.College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics,Nanjing 210016 , China ；2.Shenyang Aircraft Design and Research Institute, Aviation Industry Corporation of China,Shenyang 110000 , China ；3.Aerospace Precision Production Co., Ltd., Tianjin 300300 , China ；4.Tianjin Key Laboratory of Fastening Technology, Tianjin 300300 , China
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| Abstract: |
| Aluminum coatings are applied to the surface of titanium alloy fasteners to prevent galvanic corrosion when these fasteners are connected to aluminum alloy structural components. However, because of the complex geometries of these bolt surfaces and influences of the spray-operation parameters, such aluminum coatings often have an uneven thickness. This inconsistency can lead to bolt connections with decreased reliability and galvanic corrosion protection. Presently, there is a lack of extensive research on the factors affecting the uniformity of these coatings. This study utilized the Euler-Lagrange method to develop a physical model of the two-phase flow in an atomizing spray field. This innovative model was designed to explore how variables like the spray distance, air intake pressure, and sector control pressure impacted the thickness of the coatings applied to bolt surfaces. To verify the theoretical insights provided by the model, a series of corresponding spray experiments were meticulously conducted, and their outcomes were compared with the simulation results. The findings showed that at shorter spray distances, there was a significant variation in the velocity of droplets as they hit different parts of the bolt, leading to a generally thicker and more uneven coating. A notable issue was the greater deposition of paint at the base of the threads, where the coating thickness sometimes exceeded 30μm. When the spray distance was increased, the droplets spread out more, complicating their interaction with the environment and making their trajectory harder to predict. This often resulted in a thinner and less uniform coating on the bolt surface. The role of the air intake pressure was found to be crucial in determining the degree of paint atomization. At lower intake pressures, the atomization process was incomplete, producing larger droplets with an uneven distribution across the surface, which led to the formation of uneven patches. At higher intake pressures, the droplets became excessively fine, spreading across a larger area but ultimately resulting in a thinner coating layer on each individual bolt. The process of adjusting the sector control pressure was instrumental in changing the trajectory of the paint droplets. This adjustment significantly affected the overall spray pattern and specific placement of droplets on the target surface. At lower sector control pressures, the liquid spray was more concentrated within a smaller angular range, resulting in a thicker coating. In contrast, higher sector pressures broadened the overall spray range but caused droplets in the central area of the spray cone to lose momentum and scatter to the sides, which led to a thinner coating. Simulations indicated that the most uniform coating thickness was achieved with a spray distance of approximately 190 mm, an air intake pressure of approximately 0.4 MPa, and a sector control pressure of approximately 0.1 MPa. To verify the accuracy of the simulation in predicting the characteristics of the bolt coating formation and thickness, corresponding parameter experiments were conducted. These experiments were carried out using an automated spraying device. After the coating application and curing, the bolts were sectioned and encapsulated in epoxy resin. The coating thickness was carefully observed and recorded using a metallurgical microscope at a magnification of 400×. These results were then compared with the simulation results. A good correlation between the experimental and simulation outcomes was observed, confirming the feasibility of using the two-phase flow physical model for studying the spray field and predicting the distribution of the coating thickness. This study adopted the Euler-Lagrange method to simulate the process of spraying a bolt surface. The distribution of the coating thickness was analyzed, and a viable method for optimizing the spray parameters was developed. |
| Key words: spray flow field aluminum coating computational fluid dynanics (CFD) coating uniformity |
