利用OH-PLIF技术显示超声速燃烧的火焰结构

Reveal the Flame Structure of Supersonic Combustion Using OH-PLIF Technology

针对在来流马赫数为1.72的空气来流中横向喷注氢气发生超声速燃烧的流场,利用平面激光诱导氢氧基荧光(OH-PLIF)技术,对超燃燃烧室中三个不同的流向截面进行了二维成像测量。选择波长为283.553nm的染料激光倍频光作为激发光,可近似认为获得的OH基荧光信号强度与OH基的摩尔分数成正比。瞬态的OH基PLIF图像揭示了超声速燃烧火焰结构具有高度湍流特性,在凹腔内部存在稳定的燃烧区,为整个燃烧反应提供值班火焰,起到了促进和稳定超声速燃烧的作用。超燃火焰在沿流向传播的同时还沿径向传播,凹腔展向尺度增大时火焰沿流向的火焰区会有所减小。

Planar laser induced hydroxyl fluorescence （OH-PLIF） technology has been used to image the hydroxyl of supersonic combustion supplied by the hydrogen fuel being ejected to the maeh 1.72 fi＇eestream in the three different streamwise sections. Employing a frequency-doubled dye laser with wavelength of 283. 553nm as exciting laser, the fluorescence intensity of hydroxyl is nearly indirect proportion to the mole fraction of hydroxyl. The highly turbulem flame structure of supersonic combustion has been revealed from the instantaneous PL/F images of hydroxyl.The steady combustion in the cavity can offer on-duty flame stimulating and stabilizing the supersonic combustion. The flame spreads in the radial direction as well as in the stream direction. Having bigger spreading scale of the cavity, the streamwise flame region would diminish a little.