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This work experimentally investigated the broad ranges of dimethyl ether (DME) additions (0−100%) to ethylene on soot formation at different scales (combustor diameter) by both optical diagnostic and sampling methods. According to the optical result by a two-color method, the overall temperature and soot concentration increased slightly when DME was added from 0 to 10% but they decreased rapidly with much DME addition from 20 to 100%. Such a synergistic effect was more pronounced in the larger combustor diameter. For the sampling result of transmissions electron microscopy images, soot morphology and nanostructure transitions could be clearly observed with various DME additions. The generated soot showed typical chain-like aggregates and fullerenic-like structures with 0−10% DME additions, but more film-like materials and amorphous structure were presented as DME was added beyond 20%. Through further lattice fringe analysis, the synergistic effect of DME addition could also be reflected on the soot nanostructure. Furthermore, a high correlation between soot formation and exhaust gas composition was detected. The concentrations of CO and H 2 in exhaust gases decreased first and then increased with continuous DME additions to the fuel, peaking at 10% addition, which was exact opposite to the synergistic effect of DME addition soot formation.

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