Authors: Yong Ren Tan, Maurin Salamanca, Laura Pascazio, Jethro Akroyd, and Markus Kraft*

• Soot formation investigated in ethylene/PODE₃ laminar diffusion flames
• Increasing PODE₃ showed non-monotonic trend in soot volume fraction (SVF)
• SVF and average particle size increased with small addition of PODE₃
• Fuel-specific pathways likely contribute to the difference in soot growth
• PSDs for ISF-4 ethylene coflow diffusion flame were reported for the first time

This paper investigates the effect of poly(oxymethylene) dimethyl ether (PODE₃) on soot formation in ethylene/PODE₃ laminar coflow diffusion flames. The flames were fuelled using ethylene/PODE₃ mixtures, where up to 20% of the total carbon in the mixture was substituted with PODE₃. Flame temperature measurements suggest that differences in the soot formation in the flames are more likely due to a chemical effect rather than a temperature effect. Colour ratio pyrometry and differential mobility spectrometry were used to measure the soot volume fraction and the particle size distribution of the flames. PODE₃ was observed to be effective in reducing soot formation in previous engine studies. However, for the laboratory flames studied in this work, it was observed that introducing low levels of PODE₃ actually increased the amount of soot. When PODE₃ was blended with ethylene at 5%, there was an increase of about 10% in the soot volume fraction and about 6% in average particle size compared to the pure ethylene flame. Consideration of the chemical pathways suggests that this interaction is specific to C2 chemistry. Only when the amount of PODE₃ was increased to 10% and 20% did the soot volume fraction and average particle size decrease compared to the pure ethylene flame. The results suggest that blending sufficient amounts of PODE₃ with fuels could reduce soot formation, but that the use of too little PODE₃ could increase soot formation in the cases of fuels that produce a substantial amount of C2 species in fuel-rich regions of an engine.

• This paper draws from preprint 255: The effect of poly(oxymethylene) dimethyl ethers (PODE₃) on soot formation in ethylene/PODE₃ laminar coflow diffusion flames
• Access the article at the publisher: DOI: 10.1016/j.fuel.2020.118769

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