空气射流冷却条件下BNbRE钢轨温度场分布

Temperature field distribution of BNbRE steel rail during air-jet cooling

采用Fluent软件,基于标准k-ε湍流模型对BNbRE钢轨在空气射流冷却过程的流场和温度场进行了有限元模拟,讨论了不同冷却风速(100、200 m/s)下钢轨二维模型的温度场及传热特性变化规律。结果表明:随着风速提高,钢轨表面传热系数增大,换热效果增强;对于风速为100 m/s的情况,当冷却时间达到80 s时,上部射流与壁面冲击后产生的贴壁气流分散到两侧,会影响下部射流方向;当风速为200 m/s,冷却时间为40 s时,贴壁气流已明显影响了两侧下部射流;将风速从100 m/s提高到200 m/s后,钢轨的冷却速率明显加快,表面终冷温度从543℃降至358℃,平均冷却速率也由2.55℃/s增加至4.42℃/s,这对于满足钢轨淬火冷却工艺的要求,从而控制最终组织具有重要理论指导意义。

Flow and temperature fields of BNbRE steel rail during air jet cooling process was calculated by Fluent software based on the standard κ-ε turbulence model, 2D models temperature field and the heat transfer characteristics change of the rail under different wind speed cooling（ 100, 200 m/s） was discussed. The resuhs show that the rail surface heat transfer coefficient increases, and heat transfer enhances with the wind speed increasing. Under 100 m/s inlet velocity condition, when the cooling time reaches 80 s, the gas dispersion produced by the upper jet impact with the wall will affect the lower part jet direction. Compared with the former, when the inlet velocity is 200 m/s and the cooling time is 40 s, the adherent air flow significantly affect both sides of the lower part of the jet. The cooling rate of rail is significantly increased when the inlet velocity increased from 100 m/s to 200 m/s, the final cooling temperature decreased from 543 ℃ to 358 ℃, the average cooling rate increased from 2.55 ℃/s to 4.42 ℃/s. The model has important significance for the requirements of rail quenching process, thereby controlling the final microstructure.