天大：基于分子动力学的超临界二氧化碳布雷顿循环混合工质黏度预测

　　近日，天津大学机械工程学院赵力课题组硕士研究生薛娟在The Journal of Supercritical Fluids上发表论文：“Molecular dynamics investigation on shear viscosity of the mixed working fluid for supercritical CO₂ Brayton cycle（基于分子动力学的超临界二氧化碳布雷顿循环混合工质黏度预测）”。

　　本文利用分子动力学模拟和理论模型计算了CO₂+N₂+O₂和纯CO₂的黏度。与NIST数据库相比，纯CO₂剪切黏度的相对偏差小于1%。接着，讨论了杂质气体N₂和O₂对超临界CO₂黏度的影响。

　　结果表明：当超临界CO₂中混入杂质气体N₂和O₂时，黏度会随着杂质气体摩尔分数的增加而增加。在15MPa和827K条件下，当系统中N₂和O₂的摩尔分数达到20%时，黏度的最大相对变化可达5.72%。在这项工作中预测的超临界混合气体黏度将指导超临界CO₂布雷顿循环的设计和优化。

Graphical abstract

Fig. 4 Shear viscosity calculated with different runs.(a) the shear viscosity for 20 independent runs; thickest red line in the figure represents the average of 20 independent running. (b) Effects of the number of independent runs on shear viscosity; purple points represent the shear viscosity of each independent run.

Fig.7  Shear viscosity at a pressure of 15 MPa as a function of temperature for CO₂ + N₂ + O₂. (a)xCO₂=99mol%；(b)xCO₂=95mol%；(c)xCO₂=90mol%;(d)xCO₂=85mol%；(e)xCO₂=80mol%.  Uncertainties of 15 independent runs are indicated by error bars.

　　论文链接：https://doi.org/10.1016/j.supflu.2022.105533