正癸烷燃烧反应中OH,CH和C2自由基的瞬态发射光谱

采用ICCD瞬态光谱测量系统和加热激波管,在点火压力2.0atm,点火温度1 100～1 600K,当量比1.0,燃料摩尔分数1.0%条件下,实时测得了正癸烷/氧气/氩气燃烧过程的瞬态发射光谱,光谱范围200～850nm。结果显示燃烧过程中主要发射光谱带归属于小分子中间产物OH,CH和C2自由基,光谱强度的变化反映了燃烧过程中三种自由基浓度的变化历程;正癸烷燃烧过程中光谱强度峰值之比大于同为链烷烃的正庚烷相应OH/CH峰强度之比,揭示出两种链烃燃烧反应机理有较大差异。实验还获得了正癸烷燃烧过程中能显示谱带转动结构的CH和C2高分辨特征发射光谱。实验结果对了解正癸烷燃烧性质和验证正癸烷燃烧反应机理很有意义。

Transient emission spectra from OH, CH and C2 free radicals in the combustion reaction of n-decane

Using an intensified spectroscopic detector CCD and a heated shock tube, transient emission spectra of n-decane in the combustion reaction were measured in a spectral range of 200-850 nm. Experiments were conducted at temperatures of 1100-1600 K, a pressure of 2.0 atm, an initial fuel mole fraction of 1.0% and an equivalence ratio of 1.0. Results show that the main emission bands are attributed to OH, CH and C2 radicals produced during the combustion process of n-decane. Emission intensities of the three radicals reached their maximums only after 5 micros from the onset of their ignitions. After about 30 micros had passed, the band of OH radical was still observed, but the bands of CH and C2 radicals almost disappeared. Time histories of spectral emission intensities represent the time histories of concentrations of the three radicals during the process of combustion The emission peak ratio of OH (306.4 nm)/CH(431.4 nm) is approximately 27/100 in the combustion of n-decane, which is much greater than the corresponding ratio of about 7/100 in the combustion of n-heptane. This result reveals that the two fuels have different reaction mechanisms. High resolution characteristic spectra of CH and C2 were also acquired in the present experiment, the spectra show the rotational structures of the bands clearly. Current results are valuable for understanding the property and validating the mechanism of n-decane combustion reaction