一种新型非平行光消光法在碳烟测试中的应用

为解决高压火焰测试时平行光消光法在碳烟测试过程中会发生波束偏移,严重影响测试精度的问题,设计并搭建了一套非平行光二维测试系统. 在常压下获取了乙烯层流扩散火焰的碳烟浓度透射率图片,通过与相同条件下基于平行光消光法测试得到的结果进行对比,发现非平行光消光法具有更好的削弱波束偏移影响的能力. 结合使用Abel层析反演算法对视场累计数据进行解析,非平行光消光法能够更精确获取乙烯扩散火焰中的径向碳烟浓度分布,同时在低碳烟浓度区域噪声更低,证明了该方法是一种高灵敏度测量方法. 

Application of a Novel Uncollimated Light Extinction for Soot Concentration Measurement

The sensitivity of the light extinction technique for soot measurement using a collimated light source was limited by beam steering. The problem becomes more pronounced when the technique was applied to high-pressure flames. A novel optical system was designed and built using an uncollimated light source to mitigate the beam steering effect. Two-dimensional transmissivity images obtained in a laminar coflow ethylene diffusion flame at atmospheric pressure with the uncollimated light source were shown to be more resistant to beam steering compared to those with a collimated light extinction. Through Abel inversion the radially resolved soot volume fraction distributions at different heights with uncollimated and collimated light extinction were in good agreement. The transmissivity profiles with the uncollimated light source suffer much lower levels of noise low in the flame and just outside the flame sheet. This study found that the uncollimated light extinction is a more sensitive and effective technique for soot concentration measurement in laminar axisymmetric flames. This technique will be applied to laminar axisymmetric flames at elevated pressures in the next step.