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• The ignition delay times of natural gas mixtures diluted in CO 2 were measured. • The OXY-NG model was proposed for the natural gas oxy-fuel combustion and validated by the experimental data in the pressure range of 1–260 bar. • As the equivalence ratio increases, the ignition delay times of natural gas with CO 2 dilution increase at the pressure of 2 bar, whereas those decrease at the pressure of 250 bar. • The chaperon effects of CO 2 related to H + O 2 (+M) ⇔ HO 2 (+M) promote the ignition at fuel-rich conditions but inhibit the ignition at fuel-lean condition. Pressurized oxy-fuel combustion has attracted considerable attention as an efficient technology with lower emissions. Natural gas, which primarily consists of methane, ethane, and propane, is a widely used fossil fuel owing to its safety and low cost. The auto-ignition of 90 %methane/9 %ethane/1 %propane mixture diluted in CO 2 or N 2 were investigated using a shock tube at temperatures of 1280–1645 K, pressures of 2 and 10 bar, and equivalence ratios of 0.5–2.0 in this study. An updated model named OXY-NG can accurately predict the ignition delay times, species yields, and laminar flame speeds of natural gas mixtures in oxy-fuel and air combustion modes. The ignition delay times increased as the equivalence ratios increased related to the recombination of CH 3 radicals at 2 bar but decreased as the equivalence ratios increased owing to reactions involving HO 2 at 250 bar. The diluent CO 2 has inhibitory effects on ignition compared with N 2 , and these effects were minor under high pressure and fuel-rich conditions when diluted in CO 2. The effects on natural gas mixture ignition owing to chemical and physical properties of CO 2 are discussed in detail. [ABSTRACT FROM AUTHOR]

• The ignition delay times of CH 4 /C 3 H 8 mixtures in ratios from 90/10% to 70/30% diluted in CO 2 were measured at pressures of 1.75 and 10 atm. • The addition of propane promotes the ignition significantly in the C 3 H 8 proportion range from 0 to 30% in both cases of CO 2 and N 2 , but has slight effects on the ignition with the C 3 H 8 proportion more than 30%. • The fast increase of the methyl radicals in the initial stage is through C 3 H 8 (+M) ⇔C 2 H 5 + CH 3 (+M) owing to the easier breaking of C-C bonds in propane, which enhances CH 3 + HO 2 ⇔OH + CH 3 O, consequently promoting the ignition. • The effects of CO 2 on the promoting influence of C 3 H 8 addition are slight. • H + O 2 (+M) ⇔HO 2 (+M) suppresses the ignition at the fuel-lean condition but promotes the ignition in stoichiometric and fuel-rich conditions at 10 atm. Pressurized oxy-fuel combustion has gained great interest owing to its low emission and high efficiency. Methane and propane are important composition of natural gas, which is a clean fossil fuel and widely utilized for combustion applications including gas turbines. In this work, the auto-ignition properties of CH 4 /C 3 H 8 mixtures in ratios from 90/10% to 70/30% diluted in CO 2 were measured at pressures of 1.75 and 10 atm; equivalence ratios of 0.5, 1.0, and 2.0; and temperatures in the range of 1240–1520 K in a shock tube. Four key reactions in the Oxymech 2.0 model were updated and the modified model shows reasonable performance in both the ignition delay time and the laminar flame speed predictions in O 2 /N 2 and O 2 /CO 2 atmospheres. Two kinetic models (NUIG 1.0 and AramcoMech 3.0) were evaluated by present data and the laminar flame speed from the literature. The results of the experiment and calculation show that the addition of propane promotes the ignition significantly in the C 3 H 8 proportion range from 0 to 30% in both cases of CO 2 and N 2 , but has slight effects on the ignition with the C 3 H 8 proportion more than 30%. The effects of CO 2 on the promoting effects of C 3 H 8 addition are slight. The ignition delay times increase with the equivalence ratio at 1.75 atm but no statistical difference is observed between the measured data of different equivalence ratios at 10 atm. The influence of C 3 H 8 addition and the equivalence ratio on the ignition delay of CH 4 /C 3 H 8 mixtures was also analyzed in detail. [ABSTRACT FROM AUTHOR]

• Measure the ignition delay times of C 5 H 12 and C 3 H 6 under O 2 /CO 2 atmospheres. • The Oxymech3.0 model is developed by updating several important reactions based on the Oxymech2.0 Plus. • Develop a detailed model for C 1 -C 5 alkane, C 2 -C 3 olefin under both conventional and oxy-fuel atmospheres. • The chemical effects of CO 2 mainly caused by the chaperon effects of CO 2 for both n-C 5 H 12 and C 3 H 6. The combustion chemistry kinetics of fossil fuels under O 2 /CO 2 atmospheres and high pressures attract the attention of researchers, since the pressurized oxy-fuel combustion (POC) is seen as a promising technology for capturing CO 2 from thermal power industry and exhaust gas recirculation (EGR) is a promising technology to reduce NO x emissions. N-C 5 H 12 is a representative fuel as gasoline components, and C 3 H 6 is an important intermediate product in the oxidation of n-C 5 H 12. In this study, the ignition delay times of n-C 5 H 12 and C 3 H 6 diluted in CO 2 are measured at pressures of 1 and 10 atm under O 2 /CO 2 atmospheres at three equivalence ratios (0.5, 1.0, and 2.0) in a shock tube, respectively. A detailed model named as Oxymech3.0 is developed based on the last version, Oxymech2.0 Plus. The model is evaluated with the experimental results in this work, as well as the ignition delay times of n-C 5 H 12 and C 3 H 6 in conventional atmospheres, the laminar flame speeds of n-C 5 H 12 and C 3 H 6 , and the species profiles of n-C 5 H 12. The evaluation results of Oxymech3.0 model are compared with several existing models and show the updating reactions in this work improve the prediction of the n-C 5 H 12 and C 3 H 6 IDTs in O 2 /CO 2 atmospheres. The effects of reactions with CO 2 for n-C 5 H 12 and C 3 H 6 are very faint. The chemical effects of CO 2 mainly caused by the chaperon effects of CO 2 for both n-C 5 H 12 and C 3 H 6. For n-C 5 H 12 , the chaperon effects are sourced from the third-body collision reactions 2CH 3 (+M) ⇔ C 2 H 6 (+M) (R2652), CH 3 + H (+M) ⇔ CH 4 (+M) (R2637), and C 2 H 2 + H (+M) ⇔ C 2 H 3 (+M) (R2714) at low pressures, while those from the pressure-dependent reactions H + O 2 (+M) ⇔ HO 2 (+M) (R2562) and H 2 O 2 (+M) ⇔ 2OH (+M) (R2571) enhance at high pressure. For C 3 H 6 , the chaperon effects of CO 2 are caused by C 3 H 5 -A + CH 3 (+M) ⇔ C 4 H 8 -1 (+M) (R1456) at low pressure and by H + O 2 (+M) ⇔ HO 2 (+M) (R2562) when the pressure is higher. [ABSTRACT FROM AUTHOR]

• Ignition delay times of dimethyl ether/ethane/O 2 /CO 2 mixtures were first provided. • OXYMECH predicts well on the IDTs of the mixtures in O 2 /CO 2 and O 2 /N 2 atmosphere. • IDTs of the mixtures first decrease and then increase as adding DME at 10 atm. • The effect of DME addition and CO 2 on the IDTs of the mixtures were analyzed. The ignition delay times (IDTs) of dimethyl ether (DME)/ethane/O 2 /CO 2 mixtures were measured in a shock tube at pressures of 0.8, 2, and 10 atm; temperatures within the range of 1126–1449 K; equivalence ratio of 0.5; and DME proportions within the range of 0–100%. Four chemical kinetic models named OXYMECH, AramcoMech 3.0, San-Diego 2016 and Wang-DME were validated using the IDTs measured in this work. The results indicate that the OXYMECH predicts well the experimental data under O 2 /CO 2 and O 2 /N 2 atmospheres. At P = 0.8 and 2 atm, T = 1300 K, the increase of the DME proportion inhibits the ignition of the mixtures under O 2 /N 2 and O 2 /CO 2 atmospheres. At P = 10 atm, T = 1300 K, the IDTs of the mixtures firstly decrease when DME proportion increases from 0 to 20%, and then increase when DME proportion increases from 20 to 100% under O 2 /CO 2 atmosphere, while the IDTs of the mixtures increase as the DME proportion increases under O 2 /N 2 atmosphere. The valley-values of the IDTs of the mixtures appear at the certain DME proportion at P = 10 atm, T = 1100 K and 1200 K under O 2 /N 2 and O 2 /CO 2 atmospheres. The analyses of sensitivity and the rate of production were conducted to interpret the effect of DME addition and the properties of CO 2 on the ignition of the DME/C 2 H 6 /O 2 /CO 2 mixtures. [ABSTRACT FROM AUTHOR]

Oxy-fuel combustion of fossil fuels based on the Allam cycle has garnered increasing attention owing to its high-power cycle efficiency in carbon capture. The submechanism of ethylene, an important intermediate product in the oxidation of long-chain alkanes, is vital for establishing chemical kinetic models of alkanes for oxy-fuel combustion. In this study, the ignition delay times of C 2 H 4 diluted in CO 2 are measured at pressures of 1 and 10 atm under O 2 /CO 2 atmospheres at three equivalence ratios (0.5, 1.0, and 2.0) in a shock tube. Meanwhile, the ignition delay times of C 2 H 4 / n -C 4 H 10 mixtures and n -C 4 H 10 / i -C 4 H 10 mixtures diluted in CO 2 are measured at pressures of 1 and 10 atm, equivalence ratios of 1.0, and three mixing ratios (1:2, 1:1, and 2:1). The C 2 H 4 submechanism in the Oxymech2.0 Plus model proposed in our previous study is modified by updating some C 2 H 4 -related reactions. The modified Oxymech model, NUIGMECH1.1, and Wang2021 are evaluated based on the present experimental ignition delay times and other experimental results from the literature, including the ignition delay times of C 2 H 4 diluted in both CO 2 and conventional atmospheres, as well as the laminar flame speeds of C 2 H 4 and C 2 H 4 profiles in pyrolysis. The results show that the modified Oxymech model accurately predicts the experimental results. The modified Oxymech model is compared with NUIGMECH1.1 to predict the ignition delay times in CO 2 atmospheres and laminar flame speeds more accurately. The effects of CO 2 on the ignition delay of C 2 H 4 are discussed comprehensively. [ABSTRACT FROM AUTHOR]

• The IDTs of DME /propane mixtures in O 2 /CO 2 atmospheres were measured. • A detail kinetic model referred as the DME-C 3 H 8 model was constructed. • The effects of the DME blending ratio were studied using the DME-C 3 H 8 model. • The effects of CO 2 and pressure on the ignition were discussed in detail. This work measured the ignition delay times (IDTs) of dimethyl ether (DME)/propane mixtures in O 2 /CO 2 atmosphere in a shock tube at an equivalence ratio of 0.5, a temperature range of 1157–1380 K, pressures of 2 and 10 atm, and a DME blending ratio range of 0–100%. A detailed kinetic model referred to as the DME-C 3 H 8 model was constructed based on the OXYMECH 2.0 model and the DME sub-mechanism of Aramco 3.0. The DME-C 3 H 8 , Aramco 3.0, NUIG 1.0, and Dames models were evaluated through the IDTs obtained in the present study, and from literature in O 2 /N 2 and O 2 /Ar atmosphere. The impact of the DME blending ratio was investigated using the DME-C 3 H 8 model, and results show that the IDTs in O 2 /CO 2 atmosphere at pressures of 2 and 10 atm decrease linearly with increased DME blending ratio; there exists a clear synergy effect between DME and propane in the O 2 /N 2 atmosphere at the pressure of 2 atm, which is significantly weakened at the pressure of 10 atm. The impact of CO 2 and pressure on the ignition were discussed in detail. [ABSTRACT FROM AUTHOR]

The Dimethyl ether (DME) kinetic model is significant to understand the DME combustion in the atmosphere containing high CO 2 concentration, such as pressurized oxy-fuel combustion process and exhaust gas recirculation, and design the combustor. In this paper, the ignition delay times (IDTs) of DME were measured in a shock tube under the conditions of equivalence ratios of 0.5, 1 and 1.5, temperature ranges from 1007 K to 1340 K, and pressures of 2 and 11 atm. A detailed kinetic model of DME named as OXYDME was put forward based on the OXY-Aramco model, and was validated by the low and high temperature IDTs, laminar flame speeds, and species profiles measured in this work and those from literatures in atmospheres of O 2 /Ar/CO 2 , O 2 /N 2 , O 2 /N 2 /He/CO 2 and O 2 /CO 2. The OXYDME model was compared with OXY-Aramco, Liu-DME model in detail. The effects of CO 2 on the DME ignition are very weak and not sensitive to the temperature and pressure. The reason for the weak effects of CO 2 is that the chemical effects of CO 2 promote ignition, which counteracts the inhibition effects caused by the physical properties of CO 2. The chaperon effects of CO 2 dominate the chemical effects. Meanwhile, the effects of the reactions with CO 2 are very small. [ABSTRACT FROM AUTHOR]

Understanding the details of pyrrole combustion chemistry in the O 2 /CO 2 atmosphere contributes to developing the strategies for nitrogen oxides (NOx) control during the pressurized oxy-coal combustion (POCC). However, the existing kinetic models for pyrrole oxidation lack multi-dimensional validation, and the ignition delay times (IDTs) of pyrrole in the O 2 /CO 2 atmosphere are still scarce. This study measured the IDTs of pyrrole in O 2 /CO 2 atmospheres at an elevated pressure of 5.2 bar, temperatures from 1271 to 1645 K, and equivalence ratios Φ = 0.5, 1.0, and 2.0 in a shock tube. The results demonstrate that the pyrrole IDTs decrease with decreasing equivalence ratio and the pyrrole mixtures in O 2 /CO 2 atmospheres have longer IDTs than those in O 2 /Ar atmospheres. A pyrrole oxidation kinetic model (HUST pyrrole model) has been developed by updating 19 reactions in our previous model (HUST pyridine model). HUST pyrrole model gives a satisfactory prediction of the IDTs of pyrrole in the O 2 /Ar atmosphere (measured by MacNamara et al.) and O 2 /CO 2 atmosphere (measured in this study) and the profiles of pyrrole, HCN, and NO (measured by Yamamoto et al.). The comparison of the HUST pyrrole model with the Lumbreras model (2001) was conducted by the pyrrole IDTs and profiles of HCN using the sensitivity and flux analysis. The addition of HNCPROP and modification of R665 (C 3 H 3 + O 2 = CH 2 CO + HCO), R1273 (AC 3 H 4 CN + H 2 => ALLYLCN + H), R1251 (PYRLNE = ALLYLCN), R1238 (PYRROLE + H = PYRLYL + H 2), and R1240 (PYRROLE + OH = PYRLYL + H 2 O) in HUST pyrrole model significantly improve the prediction performance for the pyrrole oxidation. The effects of the equivalence ratio and CO 2 on the IDTs for pyrrole oxidation have been analyzed. [ABSTRACT FROM AUTHOR]