In cooling microchannels of advanced flight engines, the fuel temperature rapidly increases to facilitate endothermic cracking reactions. A cooling channel can be divided into noncracking and cracking zones. In this study, various aspect ratios were investigated via numerical simulations to determine the effects of microchannel geometry on the cooling effect. A nine-species surrogate fuel is introduced to predict the corresponding thermophysical properties. Then, one primary and three secondary cracking reactions are applied to simulate thermal cracking. The effect of the aspect ratio on the cooling performance varies in different zones. A higher aspect ratio contributes positively to a higher turbulence kinetic energy in the noncracking zone, resulting in better cooling performance. Conversely, a lower aspect ratio increases the microchannel residence time, promoting endothermic cracking reactions for an improved cooling effect. Furthermore, a cooling microchannel with a high aspect ratio in the noncracking zone and a low aspect ratio in the cracking zone is studied. The variable aspect ratios allow for leveraging of the chemical heat sink and improving the cooling performance.

在冷却高级飞行发动机的微通道中，燃料温度迅速升高以促进吸热裂化反应。冷却通道可分为非破裂区和破裂区。在这项研究中，通过数值模拟研究了各种长宽比，以确定微通道几何形状对冷却效果的影响。引入了九种替代燃料来预测相应的热物理性质。然后，进行一次和三个次要裂解反应以模拟热裂解。长宽比对冷却性能的影响在不同区域中有所不同。较高的纵横比将对非裂化区中较高的湍流动能产生积极影响，从而实现更好的冷却性能。反过来，较低的纵横比会增加微通道的停留时间，从而促进吸热裂化反应，从而改善冷却效果。此外，研究了在非裂化区域中具有高纵横比而在裂化区域中具有低纵横比的冷却微通道。可变的纵横比允许利用化学散热器并改善冷却性能。