TY - JOUR
T1 - Effect of dimethyl ether (DME) addition on sooting limits in counterflow diffusion flames of ethylene at elevated pressures
AU - Li, Zepeng
AU - Amin, Hafiz M.F.
AU - Liu, Peng
AU - Wang, Yu
AU - Chung, Suk H.
AU - Roberts, William L.
PY - 2018/11
Y1 - 2018/11
N2 - The effects of dimethyl ether (DME) addition to ethylene fuel on sooting tendencies with varying pressure were investigated in counterflow diffusion flames by using a laser scattering technique. Sooting limit maps were determined in the fuel (XF) and oxygen (XO) mole fraction
plane, separating sooting and non-sooting regions. The results showed
that when DME is mixed to ethylene, the sooting region was appreciably
shrank, especially in the cases of soot formation/oxidation (SFO) flames
as compared with the cases of soot formation (SF) flames. This
indicated an inhibiting role of DME on sooting. An interesting
observation was that the critical XO required for sooting initially decreased and then increased with the DME mixing ratio to ethylene β
for the cases of SF flames, exhibiting a non-monotonic behavior. This
implied a promoting role of DME on sooting when small amount of DME is
mixed to ethylene. As the pressure increased, the sooting region
generally expanded. Specifically, the range of β in promoting
soot formation extended with pressure. This implies that a strategy in
reducing soot by adding DME to ethylene at high pressures required a
large amount of DME addition. To interpret the observed phenomena,
kinetic simulations including reaction pathway and sensitivity analyses
were conducted with the opposed-flow flames model using the KAUST-Aramco
PAH Mech. The results showed that the thermal effect of DME addition on
sooting tendency monotonically decreases with β. The
chemical effect was found to be the main contributor to the DME addition
effect on sooting tendency, resulting in the non-monotonic sooting limt
behavior. The pathway analysis showed the role of methyl radicals
generated from DME promoted incipient benzene ring formtion when small amount of DME was added, which can be attributed to the soot promoting role of DME addition for small β.
AB - The effects of dimethyl ether (DME) addition to ethylene fuel on sooting tendencies with varying pressure were investigated in counterflow diffusion flames by using a laser scattering technique. Sooting limit maps were determined in the fuel (XF) and oxygen (XO) mole fraction
plane, separating sooting and non-sooting regions. The results showed
that when DME is mixed to ethylene, the sooting region was appreciably
shrank, especially in the cases of soot formation/oxidation (SFO) flames
as compared with the cases of soot formation (SF) flames. This
indicated an inhibiting role of DME on sooting. An interesting
observation was that the critical XO required for sooting initially decreased and then increased with the DME mixing ratio to ethylene β
for the cases of SF flames, exhibiting a non-monotonic behavior. This
implied a promoting role of DME on sooting when small amount of DME is
mixed to ethylene. As the pressure increased, the sooting region
generally expanded. Specifically, the range of β in promoting
soot formation extended with pressure. This implies that a strategy in
reducing soot by adding DME to ethylene at high pressures required a
large amount of DME addition. To interpret the observed phenomena,
kinetic simulations including reaction pathway and sensitivity analyses
were conducted with the opposed-flow flames model using the KAUST-Aramco
PAH Mech. The results showed that the thermal effect of DME addition on
sooting tendency monotonically decreases with β. The
chemical effect was found to be the main contributor to the DME addition
effect on sooting tendency, resulting in the non-monotonic sooting limt
behavior. The pathway analysis showed the role of methyl radicals
generated from DME promoted incipient benzene ring formtion when small amount of DME was added, which can be attributed to the soot promoting role of DME addition for small β.
UR - http://www.scopus.com/inward/record.url?scp=85053377189&partnerID=8YFLogxK
U2 - 10.1016/j.combustflame.2018.09.003
DO - 10.1016/j.combustflame.2018.09.003
M3 - Article
AN - SCOPUS:85053377189
SN - 0010-2180
VL - 197
SP - 463
EP - 470
JO - Combustion and Flame
JF - Combustion and Flame
ER -