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首页> 外文期刊>International Journal of Heat and Mass Transfer >Study on unsteady evaporation of n-heptane droplet in a heated tube
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Study on unsteady evaporation of n-heptane droplet in a heated tube

机译：正庚烷液滴在加热管中的不稳定蒸发研究

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Unsteady evaporation of liquid droplets and wall films is inevitable in spray combustion systems. The purpose of this study is to investigate the evaporation processes of n-heptane droplets and how they affect flame oscillation. Experimentally, a capillary tube was used to form fine tiny droplets. When the suspended droplets drip and collide with a heated tube wall, liquid film will appear, leading to Leidenfrost vaporization and flame oscillation. Theoretically, evaporation models for both suspended droplets and deposited films were built, and the calculation results were validated by experimental data. The models can accurately predict evaporation time and rate of droplets during an oscillation cycle. The results also indicate that flame oscillation only occurs when fuel supplement exceeds the consumption of evaporation. Moreover, increasing fuel flow rate or air velocity intensifies oscillation amplitude and shortens oscillation periods, but in cases where film lifetime exceeds dripping period, accumulation of liquid n-heptane occurs. Improvement of ambient temperature reduces lifetime of liquid films but extends droplet dripping periods. If vaporization rate exceeds fuel flow rate, the droplet will not drip but hang on the capillary tip with a constant diameter (d<2.62mm).
机译：在喷雾燃烧系统中，液滴和壁膜的不稳定蒸发是不可避免的。本研究的目的是研究正庚烷液滴的蒸发过程以及它们如何影响火焰振荡。实验上，使用毛细管来形成细小的液滴。当悬浮的液滴滴落并与加热的管壁碰撞时，将出现液膜，从而导致莱顿弗罗斯汽化和火焰振荡。从理论上讲，建立了悬浮液滴和沉积膜的蒸发模型，并通过实验数据验证了计算结果。该模型可以准确预测振荡周期内的蒸发时间和液滴速率。结果还表明，仅当补充燃料超过蒸发量时才会发生火焰振荡。此外，增加燃料流量或空气速度会增大振荡幅度并缩短振荡周期，但是在膜寿命超过滴落周期的情况下，会发生液体正庚烷的积累。环境温度的提高会缩短液膜的寿命，但会延长液滴的滴落时间。如果蒸发速率超过燃料流量，液滴将不会滴落，而是以恒定的直径（d <2.62mm）悬挂在毛细管尖端上。

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