对流边界条件下超临界流体层流边界层相似解
Similarity solutions of supercritical fluids laminar boundary layers with convective boundary conditions
李桢 1杨瑞 1赵玉新 2汪元2
作者信息
- 1. 国防科技大学 空天科学学院 高超声速技术实验室,湖南 长沙 410073
- 2. 国防科技大学 空天科学学院,湖南 长沙 410073
- 折叠
摘要
在超燃冲压发动机中,燃烧室和尾喷管内的高温燃气使再生冷却通道中的流体达到超临界状态,即在对流边界条件下形成超临界流体边界层,但其基本特性尚未明晰.为此,本文通过相似性解法计算了具有对流边界条件的超临界二氧化碳(SCO2)平板层流边界层,来流压力为8 MPa.文中定义了热对流系数Mθ和局部对流换热常数c,它们分别与平板下表面热流体的温度及对流换热系数呈正相关,并分析了Mθ和c对边界层速度及温度剖面的影响.当c极小时,该问题可退化为绝热壁工况;相反,当c足够大时,它的表征类似于等温壁工况.随着Mθ和c的增大,壁面热流也增大;若来流温度为亚临界,此时边界层将出现跨临界机制,使壁面努塞尔数加剧降低.
Abstract
In a scramjet engine,the high-temperature gas in the combustor and nozzle causes the fluid in the regenerative cooling channel to reach the supercritical state.This results in the formation of a supercritical flu-id boundary layer under convective boundary conditions,yet its fundamental theory remains unclear.To this end,the similarity solution was established to calculate the supercritical carbon dioxide(SCO2)flat-plat laminar boundary layers with convective boundary conditions.The free-stream pressure is 8 MPa.Thermal convection co-efficient Mθ and local convective heat transfer constant c were proposed in this paper.They are positively correlat-ed with the temperature and convective heat transfer coefficient of the hot fluid on the bottom surface of the plate,respectively.The effects of Mθ and c on velocity and temperature profiles are analyzed.When c is extremely small,the problem can be simplified to the adiabatic boundary condition.Conversely,when c is large enough,it exhibits behavior similar to an isothermal boundary condition.As Mθ and c increase,the wall heat flux also in-creases,leading to a transcritical regime if the free-stream temperature is subcritical.This exacerbates the de-crease in Nusselt number.
关键词
超临界流体/对流边界条件/层流边界层/相似解/壁面传热Key words
Supercritical fluids/Convective boundary conditions/Laminar boundary layer/Similarity solution/Wall heat transfer引用本文复制引用
出版年
2025
NETL
NSTL
万方数据