高速电弧喷涂雾化熔滴传热过程数值分析Ⅰ.数学模型及传热参数变化规律

Numerical analysis of heat transfer behavior of atomized droplets during high velocity arc spraying:I.mathematical model and vari-ations of heat transfer parameters

关键词:  高速电弧喷涂  雾化熔滴  传热过程  数值分析  热喷涂在线监控

Key words:  hiIgh velocity arc spraying  atomized droplet  heat transfer behavior  numerical analysis  on-line thermal spraying monitor system

摘要:

采用流体力学理论、凝固理论和牛顿冷却模式,提出了高速电弧喷涂雾化熔滴传热过程的数学模型,并用一种Fe-Al合金进行数值计算,用Spraywatch-2i热喷涂监控系统测试不同喷涂距离处熔滴平均温度的变化,以验证数学模型的正确性,并分析了雾化熔滴传热参数的变化规律。结果表明,计算结果与实测数据基本吻合。雾化过程中熔滴的对流换热系数、温度、固相分数及冷却速度等传热参数呈规律性变化。直径为34μm的Fe-Al合金雾化熔滴的初始液态冷却速度达2.5×10⁶ K/s,预示涂层将具有快速凝固组织特征。

Abstract:

The hish velocity arc spraying(HVAS) process relates to very complicated heat transfer behavior.And the microstructure with rapid solidification of the coating is mainly determined by the heat transfer behavior of the droplets during atomization.The heat transfer model of atomized droplets during HVAS was developed based on the theory of fluid mechanics,solidification,and Newton cooling.And the model was solved by a numerical method using a Fe-A1 alloy to analyze the variations of the heat transfer parameters with spraying distance.Experiments were carried out to measure the changes of the average temperature of atomized droplets using Spray Watch-2ion-line thermal spraying monitor system.A good agreement between the numerical and experimental results was ob-served.The results showed that the heat transfer parameters such as convective heat transfer coefficient,temperature,solid fraction and cooling rate changed in regularity.The initial cooling rate of Fe-A1 alloy droplet was about 2.5 x 106K/s,reflecting the features of rapid solidification process.