TY - JOUR
T1 - Effect of prompt dissociation of formyl radical on 1,3,5-trioxane and CH2O laminar flame speeds with CO2 dilution at elevated pressure
AU - Zhao, Hao
AU - Fu, Jiapeng
AU - Haas, Francis M.
AU - Ju, Yiguang
N1 - Funding Information:
This work was supported by DOE NETL research Grant No. DE-FE0011822 and the Princeton Environmental Institute (PEI)-Andlinger Center for Innovative Research Awards in Energy and the Environment. Thanks to Jeffrey Santner and Stephen Klippenstein at Argonne National Lab for many helpful discussions.
Publisher Copyright:
© 2017 The Combustion Institute
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2017
Y1 - 2017
N2 - Many studies of the flame speed of hydrocarbon and oxygenated fuels show that flame speed is very sensitive to formyl radical (HCO) reactions with small species, such as HCO + M = H + CO + M (R1), HCO + O2 = HO2 + CO (R2) and HCO + X = CO + XH (X = H, OH) (R3). Through comparison among experimental measurements and kinetic model predictions, this paper investigates CH2O flame speed sensitivities to the effects of HCO prompt dissociation and CO2 third-body participation in R1. The conditions considered include atmospheric and elevated pressures as well as lean, ultra lean, and rich fuel mixtures using 1,3,5-trioxane as the CH2O precursor. The experimental results provide key validation targets for CH2O and HCO chemistry and the R1 third-body coefficient of CO2 in flames. Five mechanisms, GRI Mech 3.0 (Smith et al., 1999), Li Mech (Li et al., 2007), USC Mech II (Wang et al., 2007), HP Mech (Shen et al., 2015), and Aramco Mech 1.3 (Metcalfe et al., 2013) are compared against the experimental data. Model predictions indicate that the prompt reaction pathway has a significant effect on the flame speed. With an increase in pressure or the addition of CO2, the kinetic between the prompt reaction and R1 slightly reduces the prompt radical dissociation effect. On the other hand, an increase of O2 mole fraction enhances the prompt effect on the flame speed. Comparisons among experiments and model predictions show that the HP Mech with the prompt reactions, USC Mech, and Li Mech have better predictions of the flame speed at lean, ultra-lean, rich, and lean with CO2 conditions than GRI Mech and Aramco Mech. However, the predictions of USC Mech and Li Mech with prompt reactions show increased discrepancy between experiments and predictions. This result indicates that by including a new reaction pathway, an optimized model may fail beyond the validated experimental conditions. On the other hand, an elementary rate-based, non-optimized model like HP Mech can improve the prediction by directly adding the missing prompt reaction pathway.
AB - Many studies of the flame speed of hydrocarbon and oxygenated fuels show that flame speed is very sensitive to formyl radical (HCO) reactions with small species, such as HCO + M = H + CO + M (R1), HCO + O2 = HO2 + CO (R2) and HCO + X = CO + XH (X = H, OH) (R3). Through comparison among experimental measurements and kinetic model predictions, this paper investigates CH2O flame speed sensitivities to the effects of HCO prompt dissociation and CO2 third-body participation in R1. The conditions considered include atmospheric and elevated pressures as well as lean, ultra lean, and rich fuel mixtures using 1,3,5-trioxane as the CH2O precursor. The experimental results provide key validation targets for CH2O and HCO chemistry and the R1 third-body coefficient of CO2 in flames. Five mechanisms, GRI Mech 3.0 (Smith et al., 1999), Li Mech (Li et al., 2007), USC Mech II (Wang et al., 2007), HP Mech (Shen et al., 2015), and Aramco Mech 1.3 (Metcalfe et al., 2013) are compared against the experimental data. Model predictions indicate that the prompt reaction pathway has a significant effect on the flame speed. With an increase in pressure or the addition of CO2, the kinetic between the prompt reaction and R1 slightly reduces the prompt radical dissociation effect. On the other hand, an increase of O2 mole fraction enhances the prompt effect on the flame speed. Comparisons among experiments and model predictions show that the HP Mech with the prompt reactions, USC Mech, and Li Mech have better predictions of the flame speed at lean, ultra-lean, rich, and lean with CO2 conditions than GRI Mech and Aramco Mech. However, the predictions of USC Mech and Li Mech with prompt reactions show increased discrepancy between experiments and predictions. This result indicates that by including a new reaction pathway, an optimized model may fail beyond the validated experimental conditions. On the other hand, an elementary rate-based, non-optimized model like HP Mech can improve the prediction by directly adding the missing prompt reaction pathway.
KW - 1,3,5-trioxane
KW - CHO chemistry
KW - Formaldehyde
KW - HCO prompt reaction
KW - Laminar flame speed
UR - http://www.scopus.com/inward/record.url?scp=85020177545&partnerID=8YFLogxK
U2 - 10.1016/j.combustflame.2017.05.005
DO - 10.1016/j.combustflame.2017.05.005
M3 - Journal article
AN - SCOPUS:85020177545
SN - 0010-2180
VL - 183
SP - 253
EP - 260
JO - Combustion and Flame
JF - Combustion and Flame
ER -