On the effect of carbon monoxide addition on soot formation in a laminar ethylene/air coflow diffusion flame

Abstract

The effect of carbon monoxide addition on soot formation in an ethylene/air diffusion flame is investigated by experiment and detailed numerical simulation. The paper focuses on the chemical effect of carbon monoxide addition by comparing the results of carbon monoxide and nitrogen diluted flames. Both experiment and simulation show that although overall the addition of carbon monoxide monotonically reduces the formation of soot, the chemical effect promotes the formation of soot in an ethylene/air diffusion flame. The further analysis of the details of the numerical result suggests that the chemical effect of carbon monoxide addition may be caused by the modifications to the flame temperature, soot surface growth and oxidation reactions. Flame temperature increases relative to a nitrogen diluted flame, which results in a higher surface growth rate, when carbon monoxide is added. Furthermore, the addition of carbon monoxide increases the concentration of H radical owing to the intensified forward rate of the reaction CO + OH = CO 2 + H and therefore increases the surface growth reaction rates. The addition of carbon monoxide also slows the oxidation rate of soot because the same reaction CO + OH = CO 2 + H results in a lower concentration of OH.Crown

Sooting propensities of some gasoline surrogate fuels: Combined effects of fuel blending and air vitiation

“…More and more studies have focused on soot formation/oxidation for the last two decades, contributing to bridge the knowledge gap required to optimize fuel formulation [3,13,14]. Due to the recent development in computational power, refining the understanding of the aforementioned soot related processes can be achieved when contrasting experimental measurements with data extracted from numerical simulations of reference flames [5,15]. This method then requires sophisticated computational and experimental tools.…”

The Combustion and Emissions Performance of a Syngas-Diesel Dual Fuel Compression Ignition Engine

“…However, CO chemically promotes soot formation while H 2 chemically suppresses soot formation when they are mixed with other hydrocarbon fuels [14,16]. Although the dilution effect is usually much more significant than the chemical effect [14][15][16], the combined dilution and chemical effect of CO is less significant than that of H 2 in terms of decrease in soot formation rate. As a result, the substitution of diesel by syngas 5 caused less soot emissions than that of syngas 1, since the H 2 /CO ratio in syngas 5 was higher.…”

“…When syngas 1 fraction increased, the combustion temperature decreased owing to the significant content of inert components and incomplete combustion of H 2 and CO, which resulted in a decrease in soot oxidation rate. Meanwhile, the increase in syngas 1 fraction also caused a decrease in soot formation rate, since all components of syngas suppressed soot formation when mixed with hydrocarbon fuels due to the combined dilution and thermal effects [14][15][16]. When a small amount of diesel fuel was substituted with syngas 1, the decrease in soot oxidation rate was similar to or slightly more significant than the decrease in soot formation rate, which led to little change or a slight increase in soot emissions.…”

The effect of preferential diffusion on soot formation in a laminar ethylene/air diffusion flame

“…The flame used to investigate the effect of preferential diffusion on soot formation in this paper is a two dimensional laminar ethylene/air coflow diffusion flame that has been investigated experimentally and numerically previously [15]. The schematic flame configuration is shown in Figure 1.…”

“…The volume flow rates of air and ethylene were 284 l/min and 194 ml/min, respectively, at atmosphere pressure and room temperature condition (298 K). The spatially-resolved soot volume fraction in the flame has been previously measured by the diffuse-light two-dimensional line-of-sight attenuation (LOSA) optical diagnostic method [15]. Details of the optical diagnostic method can be found from [16].…”