Experimental and numerical study on the effect of oxymethylene ether-3 (OME3) on soot particle formation

The reduction and control of particulate matter generated by fossil fuel combustion are among the main issues for actual and future combustion devices due to the increasingly stringent emission regulations. Recently, various fuels have been investigated as a potential substitute or additive for diesel and gasoline. This work focuses on how oxymethylene ether-3 (OME3), the smallest promising OME compound, affects carbon particulate formation when blended with ethylene in burner-stabilized premixed flames at different equivalence ratios. Particle size distribution (PSD) and Laser-Induced Fluorescence (LIF) and Incandescence (LII) along with numerical (Conditional Quadrature Method of Moments – CQMOM, based on D’Anna physico-chemical soot model) investigations were conducted to study particle formation and growth in pure ethylene and ethylene/OME3 flames. The soot volume fraction and PSD indicate a reduction in the total number and the size of the soot particles at all equivalence ratios, while the number of small nanoparticles remains almost unchanged. The CQMOM model is able to predict similar trends for the soot volume fraction and, using the entropy maximization concept, the general shape of the PSD for both pure ethylene and OME3-blended flames, compared to the experimental measurements.

Further, carbon particulate matter was thermophoretically sampled in the highest equivalence ratio conditions and spectroscopically analyzed. The soot structure was investigated using UV–Visible and Raman spectroscopy, finding a slightly higher aromaticity for the pure ethylene soot. FTIR analysis showed that carbon particulate matter produced from an OME3-doped flame contained larger amounts of oxygen, mainly in the form of C=O.