An experimental and numerical study of the effects of dimethyl ether addition to fuel on polycyclic aromatic hydrocarbon and soot formation in laminar coflow ethylene/air diffusion flames

Experimental and numerical study of soot formation in laminar coflow diffusion flames of gasoline/ethanol blends

“…The reason for the sensitive response of the ethylene diffusion flame to the enhanced methyl radical formation is because methyl radical concentrations are very low in this flame. In other systems, such as those of addition of dimethyl ether (DME) to fuel in ethylene/air diffusion flames studied in [10,13], the synergistic effects on soot formation have also been observed with the addition of oxygenated fuel components, and have been attributed to specific chemical pathways, in particular the interactions of C 1 and C 2 interactions to form propargyl. As pointed out by McEnally and Pfefferle [10], however, the larger alkanes, which are a major constituent of gasoline [14], decompose more readily to methyl.…”

“…As pointed out by McEnally and Pfefferle [10], however, the larger alkanes, which are a major constituent of gasoline [14], decompose more readily to methyl. Therefore, the synergistic effect of adding a small amount of oxygenated fuels (DME and ethanol) to fuel in ethylene/air diffusion flames [9,10,13] is likely a phenomenon to C 2 fuels, but not to transportation fuels, such as gasoline.…”

Measurement of soot concentration and bulk fluid temperature and velocity using modulated laser-induced incandescence

“…9 of [17], the derivation of α gave α = 0.37 for d p = 29 nm over the temperature decay range 2900-2200 K. This is very close to our present value of 0.35 measured at 1700 K. Whilst the difference is probably within the combined uncertainty limits of the two measurements, the accommodation coefficient is expected to change with temperature, and Michelsen [20] has shown from compiling data on NO that the accommodation coefficient for NO drops with decreasing gas temperature. The axial flow velocity in the laminar diffusion flame at the 42 mm height is ~190 cm/s [16], and if we take the laser beam 1/e 2 diameter of 1.435 mm as a measure of the sample size in the axial direction, we get a residence time of 0.76 ms, which is considerably more than our measured 0.47 ms. We previously estimated self-diffusion in the laminar diffusion flame at the 42 mm height using simple hard sphere collision theory and the equation x 2 = 2Dt where x is the distance diffused in time t and D is the self-diffusion coefficient [11], and using this hard sphere data we get D = 3.6 × 10 −4 m 2 s −1 . Thus, in the measured 0.46 s the self-diffusion distance is 0.58 mm, which is appreciable compared to the sample dimensions.…”

“…18. The flow velocity on centreline in the laminar diffusion flame [16] was approximately 190 cm/s and the laser beam 1/e 2 diameter of 1.4 mm giving a gas transit time of ~75 ms. The SVF was taken as 2.5 ppm and τ s as 1.23 μs (Table 1).…”

Self-Synergistic Effect of Ethylene-Heptane Mixture on Soot Formation

“…Many researchers investigated the effects of the fuel structure on soot formation process in diffusion flame by fuel mixing, and observed the synergistic effect on PAH and soot formation in some experiments [3][4][5][6][7][8]. The synergistic effect in the process of soot formation process is defined as the case when a mixture fuel can produce more PAH and soot as compared to the respective pure fuels.…”