Zhang Junqiang, Zou Zhengping, Wang Yifan
School of Energy and Power Engineering, Beihang University, Beijing 100191, China.
National Key Laboratory of Science and Technology on Aero-Engine and Aero-Thermodynamics, Beihang University, Beijing 100191, China.
Micromachines (Basel). 2022 Apr 17;13(4):637. doi: 10.3390/mi13040637.
The precooling air-breathing technique has become a study focus in the aerospace field. Research on the internal flow and heat-transfer mechanism of the precooler is important for design and optimization. A large-eddy simulation was used to study the aerodynamic and thermal characteristics in a micropipe of the hypersonic engine precooler with supercritical methane as coolant and fuel. Under the effect of buoyancy, the high-temperature and low-density fluid near the wall in the circumferential direction gradually accumulate to the top wall. The accumulation of low-density fluid enhances the thermal acceleration effect at the top wall, which intensifies the local turbulent relaminarization and forms an M-shaped velocity distribution, resulting in the weakening of the heat transfer. On the other hand, the high-density fluid gathers to the bottom wall under the influence of gravity, the local thermal acceleration effect is weakened, and the flow heat transfer is enhanced. The influence of the relationship between the turbulent burst and the turbulent heat transfer under the effect of buoyancy is analyzed. It is found that the low-speed ejection events and high-speed sweep events are strengthened at the bottom wall, especially the low-speed ejection. However, the occurrence of these events at the top wall is restrained to a certain extent.
预冷吸气技术已成为航空航天领域的研究热点。对预冷器内部流动与传热机理的研究对于其设计与优化具有重要意义。采用大涡模拟方法研究了以超临界甲烷作为冷却剂和燃料的高超声速发动机预冷器微管道内的气动和热特性。在浮力作用下，圆周方向壁面附近的高温低密度流体逐渐向上壁面聚集。低密度流体的聚集增强了上壁面的热加速效应，加剧了局部湍流再层流化，形成M形速度分布，导致传热减弱。另一方面，高密度流体在重力作用下聚集至下壁面，局部热加速效应减弱，流动传热增强。分析了浮力作用下湍突发与湍流传热之间关系的影响。发现下壁面的低速喷射事件和高速扫掠事件增强，尤其是低速喷射。然而，上壁面这些事件的发生在一定程度上受到抑制。
