Numerical study on the phase change and spray characteristics of liquid ammonia flash spray
Numerical study on the phase change and spray characteristics of liquid ammonia flash spray
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DOI：
10.1016/j.fuel.2023.128229
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发表时间：
2023-03-31
期刊：
影响因子：
7.4
通讯作者：
Kurose，Ryoichi
中科院分区：
文献类型：
--
作者：
An，Zhenhua;Xing，Jiangkuan;Kurose，Ryoichi
氨被认为是能源系统的无碳替代燃料之一。液氨在燃气轮机中的直接利用可以降低系统的复杂性和启动时间。液氨由于沸点低，特别是在标准条件下，容易发生闪蒸。1atm下的沸点为239.7 K，这不同于传统的碳氢燃料，这给液氨喷雾和燃烧模拟带来了挑战。然而，液氨相变模型的有效性仍不清楚，需要进一步探索。因此，本工作旨在对现有的液氨闪蒸和沸腾模型进行数值评估。在欧拉-拉格朗日框架下进行了大涡模拟，考虑了液滴动力学、蒸发、沸腾、辐射和气体-颗粒相互作用。具体地说，通过将模拟结果与最近公布的氨闪蒸汽化实验数据进行比较，从穿透长度、喷雾形态和温度-直径分布规律方面对五个相变模型进行了评估。结果表明，组合模型(Zuo模型和Langmuir-Knudsen模型相结合)在过热条件下更适用，并与不同温度和压力条件下的实验结果吻合较好。随着压力的降低，蒸发速率趋于增大，导致液滴和气田温度显著降低。液滴与气相之间的相互作用受压力的影响很大。在低压下，氨蒸汽质量分数随着温度的升高先降低后增加，因此在高环境压力下只表现出正相关。最后，对粒径分布的影响进行了探讨和讨论。
Ammonia is regarded as one of the carbon-free alternative fuels for energy systems. The direct utilization of liquid ammonia in gas turbines can reduce the complexity and start-up time of the system. Liquid ammonia is susceptible to flash boiling because of its low boiling point, especially under standard conditions. The boiling point is 239.7 K under 1 atm, which is different from those of traditional hydrocarbon fuels and brings challenges for liquid ammonia spray and combustion simulation. However, the validity of phase-change models for liquid ammonia remains unclear and needs further exploration. Therefore, the present work aims to numerically evaluate the existing evaporation and boiling models for liquid ammonia flash spray. Large eddy simulations were conducted in the Euler-Lagrangian framework, considering droplet kinetics, evaporation, boiling, radiation, and gas-particle interactions. Specifically, five phase-change models were evaluated by comparing the simulation results with recently published experimental data for the vaporization of the ammonia flash spray in terms of the penetration length, spray morphology, and temperature-diameter distribution law. The results indicated that the combined model (the Zuo model combined with the Langmuir-Knudsen model) was more suitable under superheated conditions and agreed reasonably with the experimental results obtained under various temperature and pressure conditions. The evaporation rate tended to increase with decreasing pressure, leading to a significant reduction in the droplets and gas field temperatures. The interaction between the droplet and gas phases was significantly affected by pressure. The ammonia vapor mass fraction first decreased and then increased with an increase in temperature under low pressure, whereby it exhibited only a positive correlation at high ambient pressure. Finally, the effect of the particle diameter distribution was explored and discussed.