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通过建立高压环境下雾化液滴传热与冷却的理论模型,分析了钐铁合金液滴雾化凝固过程中的冷却阶段,重点讨论了环境压力和液滴尺寸对冷却行为的影响。分析结果表明,冷却过程中对流传热系数随环境压力的升高而增大,随液滴尺寸的减小而增大,尺寸越小,传热系数变化越明显;环境压力升高可使雾化液滴在0.000 2 s或更短的时间内以更大的对流传热系数进行热量传递;随环境压力的升高,液滴的冷却速率增大,形核过冷度也有缓慢增大的趋势,直径50μm以内的液滴的冷却速率达106K/s,形核过冷度达200℃以上。在实际的雾化过程中,环境压力通过减小液滴尺寸显著提高冷却速度,增大形核过冷度。
By establishing a theoretical model of heat transfer and cooling of atomized droplets in high pressure environment, the cooling phase in the atomization and solidification process of samarium-iron alloy droplets was analyzed. The influence of ambient pressure and droplet size on the cooling behavior was discussed. The results show that the convective heat transfer coefficient increases with the increase of ambient pressure and decreases with droplet size. The smaller the size, the more obvious the change of heat transfer coefficient. The higher the ambient pressure, The droplets transfer heat transfer with larger convective heat transfer coefficient in 0.0002 s or less. With the increase of ambient pressure, the cooling rate of droplets increases and the undercooling of nucleation also increases slowly Trend, the diameter of the droplets within 50μm cooling rate of 106K / s, nucleation undercooling of 200 ℃ or more. In the actual atomization process, ambient pressure significantly increases the cooling rate by decreasing the droplet size, increasing the nucleate undercooling.