This paper investigates the effect of blending dimethyl ether (DME) and ethanol on the soot transition periods in ethylene counterflow diffusion flames by using a novel optical diagnostic method. The soot critical transition point in different conditions is identified experimentally and numerically. Two kinds of flames are carried out to gain the soot critical transition point in counterflow diffusion flames by changing oxygen fraction (X_o) and changing volume flow rates of fuel and oxidizer (Q_v). The red-green-blue (RGB) ratio method is used to precisely identify the soot critical transition point, and chemical kinetic simulations are performed to analyze the detailed reaction paths. The results show that compared to the ethylene flame, the soot critical transition point occurs at a higher X_o and a lower Q_v when DME or ethanol is blended. The addition of DME and ethanol can inhibit soot formation, due to the degree of soot formation reaction being lower than the degree of the oxidation reaction in the blending flames.

本文采用新型光学诊断方法研究了二甲醚（DME）和乙醇混合对乙烯逆流扩散火焰中烟灰过渡期的影响。通过实验和数值确定了不同条件下的烟灰临界转变点。通过改变氧分数( X _o )和改变燃料和氧化剂的体积流量( Q _v ) ，进行两种火焰，以获得逆流扩散火焰中的烟灰临界转变点。采用红绿蓝（RGB）比值法精确识别烟灰临界转变点，并进行化学动力学模拟分析详细的反应路径。结果表明，与乙烯火焰相比，当DME或乙醇共混时，烟灰临界转变点出现在较高的X _o和较低的Q _v处。添加DME和乙醇可以抑制烟灰的形成，因为在共混火焰中烟灰形成反应的程度低于氧化反应的程度。