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8304217 
Journal Article 
Effects of pressure on soot formation in laminar coflow methane/air diffusion flames doped with n-heptane and toluene between 2 and 8 atm 
Gu, M; Liu, F; Consalvi, JL; Gã¼Lder, ÃL 
2021 
1 
Proceedings of the Combustion Institute
ISSN: 1540-7489
EISSN: 1873-2704 
Elsevier Ltd 
38 
1 
1403-1412 
English 
WOS:000667311600014 
Laminar coflow n-heptane and toluene doped CH4/air diffusion flames were numerically investigated under a constant carbon mass flow rate at pressures between 2 and 8 atm to study how pressure affects the sooting propensity of these two main components of surrogate fuels mimicking gasoline. Numerical simulations were performed using a detailed reaction mechanism containing 175 species and 1175 reactions and a sectional soot model. Soot inception is modeled by collisions among pyrene, BAPYR and BGHIF. Soot surface growth and oxidation were modeled using the hydrogen abstraction acetylene addition (HACA) mechanism as well as PAH surface condensation. The predicted soot concentrations were in overall good agreement with measurements. Propargyl recombination and propargyl reaction with propyne are important pathways for the formation of benzene. In methane + toluene flames, attack of toluene by H radical is an effective benzene formation pathway low in the flame, but the relative importance of benzene formation from toluene was reduced with increasing pressure. Although all the soot formation processes were enhanced with increasing pressure, PAH condensation was enhanced the most, followed by HACA and inception. At 6 and 8 atm, PAH condensation becomes comparable to HACA. The pressure dependence of the sooting propensity follows the order of methane + toluene < methane + n -heptane < methane, consistent with measurements. This result could be explained by the pressure dependence of benzene formation pathways, the kinetic effect of pressure, and the scrubbing effect of soot production on the gas-phase species involved in soot formation. 
Elevated pressure; Gasoline surrogate components; Laminar coflow diffusion flame; PAH-based soot model; Soot production