超声速燃烧中的特征尺度及影响因素

针对超燃冲压发动机典型的飞行条件,分别以氢气、乙烯和煤油(由质量分数为0.8的正十烷和0.2的三甲基苯化学替代)作为燃料,分析了超声速燃烧中的特征尺度及其影响因素,给出了细致的超燃冲压发动机工作范围,并探讨了火焰面模型在超声速燃烧数值模拟中的适用性.结果表明:从氢气、乙烯到煤油,超燃冲压发动机工作范围依次减少,丹姆克尔数(Da)呈现量级的变化,火焰模式以旋涡小火焰为主,其中Taylor尺度起着关键性作用.同时也发现:相对于亚声速燃烧,在超声速燃烧的数值计算中,对能否采用火焰面模型还需要更加仔细的考虑.

Characteristic scales and influential factors in supersonic combustion

Using the hydrogen,ethylene and kerosene (chemically surrogated by a mixture of n-decane 0.8 and 1,2,4-trimethylbenzene 0.2 by mass fraction) as fuels,the characteristic scales in supersonic combustion and the related influence factors were analyzed,and the operating range of scramjet under the typical flight conditions was calculated.At last,the applicability of flamelet model for the numerical simulation of supersonic combustion was explored.The results show that the operating range of scramjet for these fuels decreases successively and Damkohler number(Da) varies boardly in the order of magnitude,and flamelet in eddies regime is usually the main part,where Taylor micro-scale plays an important role.At the same time,it is found that the flamelet model needs to be considered carefully in numerical simulation of supersonic combustion compared with subsonic combustion.