基于500 Hz OH-PLIF技术的超声速燃烧室火焰结构

针对超声速燃烧室火焰驻留时间短和高湍流度的特点,利用500 Hz高频OH-PLIF(planar laser induced fluorescence)技术,研究了氢燃料超声速燃烧室火焰结构,结合壁面压力,获得了点火、稳焰以及熄火过程的规律。结果表明：隔离段入口来流马赫数为2的情况下,氢气当量比0.1和0.3,在火花塞点火下,2 ms均能点燃并获得PLIF火焰图像,其中当量比为0.1凹槽内存在爆燃现象,火焰达到稳定燃烧状态较慢(约65 ms)。稳焰过程中,当量比为0.3燃烧相对不充分,燃烧区域更靠近下壁面,燃烧位置和火核位置变化较大。当量比为0.1和0.3,熄火时间均在6 ms内,其中当量比为0.1熄火时火焰是从凹腔中部传播到凹腔前缘位置熄灭并伴随有一个短暂火焰增强的过程,并且在传播至凹腔前缘时已接近熄灭,当量比为0.3在熄灭前则是慢慢变弱,最终在凹腔前缘至喷氢位置间熄灭。

Flame structure in supersonic combustion chamber based on 500 Hz OH-PLIF technology,

500 Hz high-speed OH-PLIF technology was used for the research of the flame structure in supersonic combustion chamber, which was characterized by short time-lag and high turbulence in cavity chamber. Combining the pressure of the wall surface, the ignition, stabilization and extinguishing of the flame were studied. The results showed that ignition occurred when the hydrogen equivalents were 0.1 and 0.3. PLIF camera got the image in 2 ms under the spark. A detonation combustion existed in the cavity of the equivalent ratio of 0.1, and the flame was slower to reach stable state in the cavity (about 65 ms). In the process of stabilization of the flame, the equivalent 0.3 was in an incomplete combustion state, the burning area was closer to the wall, the burning position and nuclear position of the fire were greatly changed at the equivalent 0.3. At the equivalent of 0.1, the flame was transmitted from the middle of the cavity to the front edge of the cavity with a process of a briefly increased flame. Flame extinguished at the front edge of the cavity. However the equivalent 0.3 was slightly weaker, which was eventually extinguished between the front edge of the cavity and the position of hydrogen injection.