In-situ optical measurement of additive effects on particulates in a sooting diffusion flame

Influence of potassium on benzene and soot formation in fuel-rich oxidation of methane in a laminar flow reactor

“…This result is consistent with the multimodal PSD observed for the postflame region of a smoking laminar diffusion methane flame added with sodium chloride (NaCl) [45]. However, in many previous studies the addition of alkali metals was found to inhibit the size growth of soot and lead to a higher concentration of smaller soot particles, e.g., in premixed flames [25][26][27][28] and in diffusion flames [29,30]. The discrepancy between the results is attributed to the differences in experimental techniques and conditions.…”

“…While alkali earth metals are recognized to be effective fuel additives to suppress soot formation, mainly by catalyzing the production of OH (hydroxyl) radicals that rapidly remove soot [23,24], the effects of alkali metals are not clear. It was reported in several studies that primary soot particles formed in premixed hydrocarbon flames [25][26][27][28] and diffusion flames [29,30] seeded with alkali metals are characterized by smaller sizes, resulting in an overall reduction of the soot yield because smaller particles can be more easily oxidized. The decrease of soot particle size by alkali metal additives has been attributed to an ionic mechanism, where ionized alkali metals charge the neutral incipient soot particles or neutralize the positively charged particles and thus inhibit their further growth or agglomeration [29,31,32].…”

“…It was reported in several studies that primary soot particles formed in premixed hydrocarbon flames [25][26][27][28] and diffusion flames [29,30] seeded with alkali metals are characterized by smaller sizes, resulting in an overall reduction of the soot yield because smaller particles can be more easily oxidized. The decrease of soot particle size by alkali metal additives has been attributed to an ionic mechanism, where ionized alkali metals charge the neutral incipient soot particles or neutralize the positively charged particles and thus inhibit their further growth or agglomeration [29,31,32]. However, such a suppressing effect is not necessarily observed in all cases.…”

Synchrotron Radiation Studies of Additives in Combustion, II: Soot Agglomerate Microstructure Change by Alkali and Alkaline-Earth Metal Addition to a Partially Premixed Flame

“…Our results for primary size and concentration are coherent with the findings reported by Bonczyk from light scattering studies, except for the fact that, in our case, we do not observe that the decrease in size is necessarily correlated with an increase of particle concentration. In our experiments, we observe that this correlation holds true in the case of CsCl but less evidently in the cases of KCl and BaCl 2 addition.…”

“…One of the most complete studies made of this phenomenon was that of Bonzcyk, who used laser light scattering to characterize the effects of alkali salt addition to propane/oxygen diffusion flames. With this technique, he showed that the aspiration of cesium chloride into the flame resulted in a decrease in particle diameter that was proportional to the concentration of additive used with a sooting flame.…”