Technical Report 255, c4e-Preprint Series, Cambridge

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

Reference: Technical Report 255, c4e-Preprint Series, Cambridge, 2020

Associated Themes:
 

• 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 atmospheric pressure 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 (SVF) and the particle size distribution (PSD) of the flames. PODE₃ was observed to be effective in reducing soot formation due to its high oxygen content and the absence of carbon-carbon bonds as per 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 SVF 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% did the SVF decrease. A further increase in PODE₃ to 20% was observed to inhibit the particle growth, with the maximum average particle size decreasing by about 73%. 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. The data set reported with this paper includes, for the first time, PSD data for the International Sooting Flame Workshop coflow laminar diffusion flame (ISF-4 coflow 3).

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