发散冷却最小冷却介质注射量的数值研究

A numerical investigation of the minimum coolant injection rate for transpiration cooling

充分发挥材料本身的抗高温能力,以最小的冷却介质注射量,确保推进器不被烧蚀是发散冷却系统的设计目标.本文用一维可压缩、非稳态、局部非热平衡模型,数值研究了瞬态冷却过程及最小冷却介质注射量的依赖参数.数值研究表明:研究瞬态的冷却过程十分重要,因为尽管当冷却过程达到稳态以后热端温度在烧蚀点以下,但在进入稳态之前可能已经发生烧蚀;多孔介质骨架材料的初始温度越高、特征尺寸越大,冷却介质需要量越大;在仅考虑冷却效果的前提下,孔隙率越大,冷却介质需要量越大;相反,骨架材料导热系数越高,冷却介质需要量越小.

An advanced design of transpiration cooling system is not only to ensure thermal protection of propulsion system from ablation, but it also should utilize the full temperature potential of porous matrix. A numerical investigation of transient processes of transpiration cooling and the control parameters of the lowest limit of the coolant mass flow rate is conducted with the help of a compressible, unsteady and local non-thermal equilibrium model. The numerical investigation presents that it is important to study transient cooling process, because the porous matrix could be ablated before the cooling process reaches a steady state, though the steady temperature may be lower than the melting point. A higher initial temperature and a larger characteristic size of the porous matrix will result in an increase in the minimum coolant injection rate to prevent ablation of the porous matrix. From the view point of cooling effect,a higher porosity corresponds to a larger coolant mass flow rate. Contrarily, a higher thermal conductivity.of the porous matrix corresponds to a lower demand for the minimum coolant flow rate.