凹腔稳定的超声速火焰结构的实验研究

Experimental study of supersonic flame structure in cavity

关键词:  超声速燃烧  凹腔  分形维数  自发辐射

Key words:  Supersonic combustion  Cavity  Fractal dimension  Spontaneity radiation

摘要:

凹腔是高湍流度超声速燃烧的火焰稳定装置。为研究其尺寸结构及喷注位置对不同燃料燃烧性能的影响,设计了不同凹腔、不同位置横向喷注的氢及乙烯的超燃实验,拍摄了凹腔内OH.基与CH.基自发辐射火焰图像。并利用非线性分形的研究方法,分析了火焰分形维数与燃烧程度及火焰稳定性的关系。用大涡模拟方法对二维凹腔氢超燃流场进行了数值仿真,分析了凹腔流场结构,并对凹腔后缘压力时间序列进行了相空间重构,计算了其分形维数。实验及仿真结果均表明:燃烧的分形维数高时,燃料与空气接触充分,燃烧剧烈,易于火焰稳定。

Abstract:

Cavity is flame holder in high turbulent supersonic combustion.Different structural cavities,different transverse injection positions of hydrogen and ethylene were studied via experiments,and photos of OH· radicals and CH· radicals spontaneity radiation in cavities was taken.Then nonlinear method of fractal was used to analyze the relationship among fractal dimension,combustion degree,and stability of flame.Large eddy simulation was used to calculate supersonic hydrogen combustion in two dimensional cavities.And analyzed flow structure in cavity was analyzed.Phase space of pressure time series at the back edge of cavity was reconstructed.The calculation results are consistent with experiments: high fractal dimension of flame can improve mixing fuel,combustion,and flame holding.