The low flame speed and calorific value of ammonia (NH3) result in a high risk of flame blow-off during pure NH3 combustion. To address this challenge, existing porous media burners (PMBs) capable of achieving stable NH3/ air combustion exhibit complex structures and large sizes. Furthermore, the structure of the PMB becomes more complicated when two-stage combustion mode is employed to reduce NOx emissions. In this study, a porous media-wire mesh (P-W) burner composed of honeycomb ceramic and wire mesh, characterized by simple structure and low cost, is developed for pure ammonia combustion. The blow-off prevention mechanism of achieving stable NH3 combustion is analyzed by the simulation of the ignition process of the premixed NH3/air mixture in the P-W burner. The high-temperature wire mesh plays a crucial role in the formation of the NH3 flame-front, which is the key to preventing the blow-off of NH3/air combustion. The combustion stability and pollutant emissions are experimentally investigated with different pore sizes and installation heights of the wire mesh. The pore size has a significant impact on the lean blow-off limit, and the installation height has an impact on the optimal operating power of the P-W burner. The optimal pore size of 7 mm & times; 12 mm and installation height of 20 mm are identified for stable NH3/air combustion with the lowest lean blow-off limit of Phi = 0.55 at NH3 thermal power (PNH3) of 2.0 kW. The optimal pollution emissions, NO emissions of 109 ppm and undetected NH3 and N2O emissions, are achieved at Phi = 0.95 and NH3P = 2.0 kW.

Recent years have witnessed significant research efforts in developing NH3/CH4, NH3/C2H6, and NH3/C3H8 combustion models. This study quantitatively evaluates 10 existing NH3/C1-C3 models against extensive experimental data, revealing that none adequately predict NH3/CH4, NH3/C2H6, and NH3/C3H8 combustion. This limitation primarily stems from two critical factors: (1) the inherent constraints of the adopted NH3 and alkane sub-models, and (2) the omission of several key C/N cross-reactions in the reaction mechanisms. To address this gap, we measured ignition delay times (IDTs) and laminar flame speeds (LFSs) of NH3/MEP (abbreviation for the CH4/C2H6/C3H8 mixture) mixtures using shock tube and heat flux methods, systematically investigating C/N cross-reaction roles. A refined NH3-MEP model, built upon our prior work, demonstrates excellent predictive capability for NH3/CH4, NH3/C2H6, NH3/C3H8, and NH3/MEP combustion. Cross-reactions affect the combustion of two or all binary fuel mixtures among NH3/CH4, NH3/C2H6, and NH3/C3H8 systems, which are defined as universal impacts. Such cross-reactions typically occur between shared key intermediates from C1-C3 alkane oxidation and nitrogen-containing species. By analyzing the oxidation pathways of CH4, C2H6 and C3H8, we identify HCO and C2H3 as the shared key intermediates for C1-C3 and C2-C3 alkane oxidation, respectively. This work thoroughly investigates the universal effects of two critical cross-reactions: C2H3 + NH2 = C2H2 + NH3 (R1459) and HCO + NH2 = CO + NH3 (R1466). The present study also conducts an in-depth analysis of the low-to-intermediate temperature ignition behavior of NH3/CH4 blends. Shi et al.'s theoretically calculated R1009 rate constant substantially improves the NH3-MEP model's predictions of RCM-IDT for NH3/ CH4 mixtures. This study can deepen the fundamental understanding of cross-reaction mechanisms in ammonia/ alkane co-firing and provide theoretical support for the development and optimization of combustion devices utilizing NH3/natural gas (NG) fuels.

The ignition delay times (IDTs) of NH3/methyl isopropyl ketone (MIPK) mixtures with MIPK blending ratios of 5 %, 10 %, and 30 % were measured at pressures of 1.75 and 10 bar, temperatures ranging from 1100 to 2000 K, under stoichiometric condition. The IDTs were found to exhibit a sharp decrease at 5 % MIPK blending ratio and then reduced slowly with further MIPK addition. Increasing pressure could enhance the ignition-promoting effects of MIPK. A detailed MIPK-NH3 model was constructed including the MIPK sub-model, the NH3 sub-model, and the cross-reactions between C-containing species and N-containing species which consisted of the prompt NO formation reactions and reburn type reactions, the recombination and oxidation reactions of small amines, H-abstraction reactions, and disproportionation reactions. The predictions calculated by the MIPK-NH3 model are in good agreement with the measured IDTs. The analysis showed that the cross-reactions evidently inhibit the ignition of NH3/MIPK, which is mainly attributed to the disproportionation reactions; and the ignition-inhibiting effects decrease with the increasing pressure or MIPK blending ratio. The effects of the MIPK blending ratio and cross-reactions on the ignition of NH3/MIPK were analyzed in detail. The oxidation pathways of NH3/MIPK were also discussed.

Infrared radiant combustion has been widely used in household gas appliances. Metal fiber and porous ceramic are two primary types of porous materials used in the infrared radiant burner. However, the complex weaving process of metal fiber leads to prohibitive costs, and the porous ceramic burner is frequently criticized by users due to its excessively long response time. Additionally, porous ceramic burners face challenges such as susceptibility to breakage and slagging. Therefore, there is a demand for a novel infrared radiant burner combining the best features of these two porous burners for the household gas appliance. In this study, a novel infrared radiant burner, referred to as metal mesh burner, is proposed to perform premixed infrared radiant combustion. The burner, with a thickness of 1.0 mm, comprises three-layer metal mesh with pore density of 60, 10, and 60 pores per inch, respectively. One innovation of the metal mesh burner is its effective prevention of flashback within a remarkably thin structure. Another innovation is that the combustion is stabilized near the surface of the infrared radiant burner with a firing rate range of 83 to 1000 kW/m2. The metal mesh burner was experimentally tested and compared with traditional porous burners (metal fiber burner and porous ceramic burner) in terms of infrared-induced time, the range of operating conditions for stable infrared radiant combustion, and pollution emissions across different equivalence ratios and thermal power levels. In addition, the radiation efficiency and service life of metal mesh burner were evaluated. Numerical simulations were conducted to analyze the mechanism of flashback prevention and stable surface combustion in the metal mesh burner.

The ignition delay times (IDTs) of NH3/diethyl ketone (DEK) mixtures at DEK blending ratios (XDEK) of 0.05, 0.1, and 0.5 were measured in a shock tube at equivalence ratios (phi) of 0.5, 1.0 and 2.0, pressures of 1.75 and 10 bar, and temperatures from 1200 to 1900 K. The addition of DEK with XDEK = 0.05 significantly improves the combustion performance of ammonia. A detailed DEK-NH3 model was proposed including the NH3 sub-model, the DEK sub-model, and the cross-reactions between hydrocarbon/oxygenated species and nitrogen-containing species. The model well predicts the IDTs of NH3/DEK mixtures measured in this study, and the IDTs of pure NH3 reported in the literature. The cross-reactions consist of the prompt NO and reburn reactions (reaction-class 1), the recombination reactions and the oxidation reactions of small amines (reaction-class 2), the H-atom abstraction reactions (reaction-class 3), and the disproportionation reactions (reaction-class 4). The comparison of the model predictions shows that the reaction-class 1 and 2 have negligible effects on the ignition. The reaction-class 3 slightly promotes the ignition and the reaction-class 4 significantly inhibits the ignition. The dependence of the effects of the cross-reactions on the blending ratio and pressure are discussed in detail. The NH3/DEK oxidation pathway is also analyzed.

Recently, ammonia (NH3) becomes an attractive alternative fuel to reduce CO2 emissions. The combustion of NH3 mixed with reactive fuels is a feasible solution to the issue of low reactivity. In the present study, the ignition delay times (IDTs) of NH3/OME2 were measured in a shock tube at an equivalence ratio of 0.5, two pressures of 1.75 and 10 bar, and a temperature range of 1245-1797 K with OME2 mole fractions of 0.05, 0.1, and 0.2. The OME2-NH3 model was proposed including the OME2 model updated in this work, the NH3 model optimized in our previous work, and some cross-reactions between nitrogen-containing species and C1-C4 species. The OME2-NH3 model well predicts the IDTs and species profiles of NH3/OME2 and IDTs and laminar flame speeds of NH3/OME1, as well as the IDTs, laminar flame speeds, and species profiles of OME1 and OME2. The crossreactions considered in this work significantly improve the model prediction. The effects of cross-reactions on the high and low-temperature reactivity of NH3/OME2 were analyzed in detail. The comparison between the OME2-NH3 model and the Li-Shrestha model illustrated that the OME2 model updated in this work significantly improves the model prediction. This research provides archival experimental data for the NH3/OME2 ignition and provides insights into the interactions between OME2 and NH3 by the detailed numerical simulations.

A feasible solution to the low reactivity of ammonia is co-burning ammonia with highly reactive fuel, such as natural gas (NG). Ethane (C2H6) is the primary non-methane (CH4) compound in natural gas and a fundamental C-2 fuel. The C/N cross-reactions play an important role in the prediction of the combustion of NH3/C2H6 blends. The ignition delay times (IDTs) of stoichiometric NH3/C2H6 mixtures in high Ar dilution (90 %) with C2H6 fractions of 0 %, 10 %, 20 %, and 30 % were measured at pressures around 1.75 and 10 bar, and temperatures ranging from 1227 to 1890 K using a shock-tube facility. A detailed NH3/C2H6 kinetic model (NH3C2H6 model) was proposed based on the NH3 model optimized in our previous works and the PTB-NH3/C-2 model, and some new cross-reactions were considered in the NH3C2H6 model. The NH3C2H6 model was extensively validated against IDTs measured in this work as well as IDTs, laminar flame speeds (LFSs), and species profiles (SPs) of NH3/C2H6 from the literature. The cross-reactions in the PTB-NH3/C-2 model promote the ignition of NH3/C2H6 mixtures and have inhibiting effects on LFSs only at phi = 1.1-1.3 and limited effects on the NH3 consumption, which results in the obvious deviation of the prediction from the experiments. The new cross-reactions considered in the NH3C2H6 model obviously improve the prediction of NH3/C2H6 combustion. The effects of the cross-reactions on IDTs, LFSs, and SPs of NH3/C2H6 were studied in detail by the sensitivity analysis and rate of production (ROP) analysis using the NH3C2H6 model.

Ammonia is a promising alternative clean fuel due to its carbon-free, high energy density and well-established infrastructure of storage and distribution. The co-combustion with reactive fuels improves the NH3 combustion stability. Moreover, C2H4 is an important intermediate product in the oxidation of many hydrocarbon fuels. Therefore, some researchers focused the fundamental study and soot formation of NH3/C2H4 combustion. A reliable combustion model of NH3/C2H4 advances the understanding of the interaction between NH3 and C2H4. The key to develop the model of NH3 /C2H4 is the cross reactions between N-containing species and C-containing species. In this work, the ignition delay times of NH3/C2H4 mixtures were measured at three blending ratios (95 %, 90 %, 70 % NH3) at 1.75atm and 10atm in a shock tube at the temperature range of 1247 K to 1786 K. A detailed chemical kinetic model was developed on the base of our previous optimizing NH3 model and the C0C2 sub-model of NUIGMECH1.1, and some new cross reactions between N-containing species and hydrocarbon species were considered in the model. The NH3-C2H4 model is validated by the current experimental data, the laminar flame speeds of NH3/C2H4 mixtures and the species profiles of NH3/C2H4 mixtures oxidation. The cross reactions considered in this work significantly improve the prediction. The disproportionation reactions, C2H3 + NH2 <=> C2H2 + NH3 (R1466) and HCO + NH2 <=> CO + NH3 (R1465), significantly inhibit the ignition and the flame propagation, and cause the increase in the formation of HCO and HCCO with the increase of NH3 content, which facilitates the reduction of the soot formation.

Ammonia (NH3) is now attracting attention in the energy field due to its hydrogen-containing and carbon-free, vast infrastructure, safe utilization and longstanding storage. Nevertheless, NH3 combustion is usually associated with low flame instability and high NOx emissions due to its low laminar flame speed and nitrogen content. The partial catalytic cracking of NH3 offers an economical strategy to improve combustion stability. However, the significant limitations of this strategy include high NOx emissions. Therefore, the MILD combustion of partial catalytic cracking of NH3 is an excellent method to address the challenge. In this work, a novel trimetallic catalyst (Fe, Co, and Ni) was developed, and the MILD combustion of partially catalyzed NH3 and NH3/N2 was performed in a novel burner. The effects of the NH3 conversion, N2 addition and NH3 power on pollutant emissions were experimental investigated. Numerical simulations were carried out to analyze the characteristics in the MILD combustion of partially catalyzed NH3 and NH3/N2 observed in the experiments.

Ammonia (NH3) is a promising alternative clean fuel due to its carbon-free and high hydrogen content, along with the well-established infrastructure for storage and distribution. To overcome the issue of the low reactivity of NH3, a feasible strategy is co-burning ammonia with highly reactive fuels. Diethyl ether (DEE) is considered a promising alternative and biomass-oxygenated clean diesel substitute. Therefore, the NH3/DEE blend is also a promising carbon neutral alternative fuel. In this work, we measured the ignition delay times (IDTs) of NH3/DEE mixtures with DEE fractions (XDEE) of 0.05, 0.10, 0.30, and 1.00 at equivalence ratios of 0.5, 1.0, and 2.0, pressures of 1.75 and 10 bar, and temperature ranges from 1102 K to 1673 K in a shock tube. The DEE-NH3 model was proposed in this work, which included the DEE sub-model, NH3 sub-model, and some new cross-reactions between N-containing species and C-containing species. The DEE sub-model from Shrestha et al. (Fuel Communications, 2022) was modified in this work, NH3 sub-model was from our previous work (Reaction Chemistry & Engineering, 2023). The DEE-NH3 model was extensively validated by the IDTs, laminar flame speeds (LFSs), and species profiles (SPs) of NH3/DEE mixtures as well as pure DEE and NH3. The comparison of the prediction performance between the DEE-NH3 model and the Shrestha model was conducted for the ignition, flame propagation, and NH3 consumption. The effects of the cross-reactions on the NH3/DEE ignition and combustion were studied in detail.

The H -abstraction reactions and disproportionation reactions play very important roles in the NH3/CH4 combustion model. The rate coefficient of the H -abstraction reaction, CH2O + NH2--HCO + NH3 (R1430), theoretically calculated by Li & L & uuml; was multiplied by 100 in the works of Dai et al. to better match the experiment, which was repeatedly adopted in the subsequent NH3/CH4 kinetic models. Moreover, the disproportionation reaction, HCO + NH2--CO + NH3 (R1449), is not considered in the current existing NH3/CH4 kinetic models. In this work, the NH3-CH4 model is proposed including the C1-C2 sub -model, NH3 sub -model, and cross -reactions between nitrogen -containing species and hydrocarbon species including R1430 with the rate coefficient of Li & L & uuml;, and R1449. The NH3-CH4 model was extensively validated by the SPs, IDTs, and LFSs of NH3/CH4 mixtures from the literature. The effects of the H -abstraction reaction and disproportionation reactions on the profiles of CH2O, IDTs, and LFSs of NH3/CH4 are closely studied by the sensitivity analysis and the rate of production (ROP) analysis using the NH3-CH4 model, and the effects of R1430 and R1449 are discussed by the comparison among the NH3-CH4 model, KAUST model and KAUST model with original rate constants. R1430 inhibits the CH2O formation. Multiplying the rate constant of R1430 by 100 in the KAUST model significantly deteriorates the prediction of CH2O. R1449 has significant inhibiting effects on LFSs due to reducing the H production in the pathway HCO -> CO in the NH3-CH4 model. The rate constant of R1430 had to be artificially enhanced to predict well LFSs of NH3/CH4 mixtures in the KAUST model due to the absence of R1449. R1430 has significant promoting effects on IDTs, and the disproportionation reactions have a negligible influence.

The combustion chemistry kinetics of fossil fuels under O2/CO2 atmospheres and high pressures attract the attention of researchers, since the pressurized oxy-fuel combustion (POC) is seen as a promising technology for capturing CO2 from thermal power industry and exhaust gas recirculation (EGR) is a promising technology to reduce NOx emissions. N-C5H12 is a representative fuel as gasoline components, and C3H6 is an important intermediate product in the oxidation of n-C5H12. In this study, the ignition delay times of n-C5H12 and C3H6 diluted in CO2 are measured at pressures of 1 and 10 atm under O2/CO2 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-C5H12 and C3H6 in conventional atmospheres, the laminar flame speeds of n-C5H12 and C3H6, and the species profiles of n-C5H12. 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-C5H12 and C3H6 IDTs in O2/CO2 atmospheres. The effects of reactions with CO2 for n-C5H12 and C3H6 are very faint. The chemical effects of CO2 mainly caused by the chaperon effects of CO2 for both n-C5H12 and C3H6. For n-C5H12, the chaperon effects are sourced from the third-body collision reactions 2CH3 (+M) ⇔ C2H6 (+M) (R2652), CH3 + H (+M) ⇔ CH4 (+M) (R2637), and C2H2 + H (+M) ⇔ C2H3 (+M) (R2714) at low pressures, while those from the pressure-dependent reactions H + O2 (+M) ⇔ HO2 (+M) (R2562) and H2O2 (+M) ⇔ 2OH (+M) (R2571) enhance at high pressure. For C3H6, the chaperon effects of CO2 are caused by C3H5-A + CH3 (+M) ⇔ C4H8-1 (+M) (R1456) at low pressure and by H + O2 (+M) ⇔ HO2 (+M) (R2562) when the pressure is higher.

A viable strategy to improve ammonia (NH3) combustion stability is blending ammonia with high-reactivity fuels. Propane (C3H8) is the prevalent component in liquefied petroleum gas (LPG), emerging as a compelling choice for co-firing with ammonia in various practical applications. The ignition delay times (IDTs) of stoichiometric NH3/C3H8 mixtures in Ar dilution (90 %) with varying C3H8 fractions (X-C3H8) of 0-30 % were conducted at pressures of 1.75 and 10 bar, and temperatures ranging from 1305 to 1890 K in a shock tube. The NH3-C3H8 model was developed based on the NH3 model optimized by Li et al., the C3H8 submodel in the NUIG 1.1 model, and some new cross-reactions were considered in the NH3-C3H8 model. The NH3-C3H8 model was extensively validated against IDTs measured in this work as well as laminar flame speeds (LFSs) and species profiles (SPs) of NH3/C3H8 from the literature. The comparison of the prediction performance between the NH3-C3H8 model and the M-NUIG model was conducted for ignition, flame propagation, and NH3 consumption. The effects of the cross-reactions on IDTs, LFSs, and SPs of NH3/C3H8 were studied in detail by the sensitivity analysis and rate of production (ROP) analysis using the NH3-C3H8 model. The newly added C/N cross-reactions play an important role in the prediction of the IDTs, LFSs, and SPs of NH3/C3H8 combustion.

The ignition delay times (IDTs) of ammonia/dimethoxymethane (DMM) mixtures at DMM blending ratios of 5%, 10%, 15%, and 50% are measured behind reflected shock waves under the following conditions: pressures of 1 and 10 bar; equivalence ratio (& phi;) of 0.5; temperatures between 1193 and 1852 K. The DMM-NH3 model is proposed including the DMM subset, the NH3 subset, and the cross-reactions be-tween DMM and NH3. The cross-reactions consist of the prompt NO and reburn reactions, recombination reactions, H-abstraction reactions, and disproportionation reactions. The DMM-NH3 model well predicts the IDTs and laminar flame speeds (LFSs) of NH3 /DMM mixtures measured in this study and those from the literature. And the DMM-NH3 model is also validated by the IDTs, LFSs, and species profiles of pure NH3 and pure DMM reported in the literature. The effects of the prompt NO and reburn reactions, re-combination reactions, H-abstraction reactions, and disproportionation reactions are discussed in detail. The NH3 /DMM oxidation pathway is also analyzed.Novelty and Significance Statement ➢ The IDTs of NH3 /DMM mixtures at high temperature are measured.➢ The detailed DMM-NH3 model is proposed with the addition of the cross-reactions between DMM and NH3.➢ The DMM-NH3 model well predicts the IDTs and LFSs of NH3 /DMM mixtures.➢ The prompt NO and reburn reactions and the recombination reactions have negligible influence on the ignition.➢ The H-abstraction reactions slightly inhibit ignition and the inhibiting effects come from CH3OCH2OCH3 + NH2 = CH3OCH2OCH2 + NH3 (R1591).➢ The disproportionation reactions significantly inhibit ignition and flame propagation, and the inhibit-ing effects come from HCO + NH2 = CO + NH3 (R1629).& COPY; 2023 Published by Elsevier Inc. on behalf of The Combustion Institute.

Power domain sparse code multiple access (PD-SCMA) scheme-based visible light communications (VLC) can support higher spectrum efficiency and increased number of users in wireless access networks. In PD-SCMA-VLC, successive interference cancellation (SIC) and message passing algorithm (MPA)-based receivers are used to recover the transmitted signals in the power and code domains, respectively, which are complex requiring higher signal to noise ratio levels to deliver the quality of services. We propose a deep neural networks (DNN) based scheme to recover the PD-SCMA signal effected by the mixed noise, multipath distortions, and the nonlinearity due to the light emitting diode, channel and photodiode. We show by experiment that, the proposed DNN significantly outperforms the conventional SIC-MPA in terms of the achievable data rate and bit error rate performance. For DNN-based PD-SCMA-VLC, the achievable data rates are more than 100 and 120 Mbps for the user groups 2 and 1, respectively.

目的:为掌握实验室检测能力,使用国标文件"指南"推荐的方法评定不确定度,并对其存在的问题提出建议,为有关方面修订、完善"指南"提供参考.方法:采用"指南"top-down方法,利用PT数据和实验室测量复现性,评定实验室常规生化检测项目不准确度.结果:该方法为临床实验室测量不确定度评定提供了标准和依据.

Ammonia has received increasing attention as one of the most attractive energy carriers because of its carbon-free nature and the established reliable and economic infrastructure for its storage and distribution. However, the low burning velocity and nitrogen-containment of pure NH3 can cause some challenges for its combustion control such as flame instability and large NOx emissions. To overcome these issues, strategies of co-burning NH3 with highly reactive fuels such as CH4 or H2 have been developed and applied. Syngas, which can be produced from biomass pyrolysis, is a promising alternative fuel in the transition from carbon-based fuels to carbon-free fuels. Therefore, comparing to co-firing NH3 with CH4, co-firing NH3 with syngas is a better environmentally friendly option to improve the NH3 combustion property. However, co-firing NH3 with syngas faces severer combustion instability, NOx emissions and NH3 leakage due to the low heating value of syngas. To the best of the authors’ knowledge, the NH3/syngas combustion with low NOx emissions and zero NH3 leakage has not been achieved in a lab-scale combustor. In the present study, NH3/syngas MILD combustion was carried out in a novel burner developed in our previous work. In the novel burner, the high-temperature and diluted air produced by the lean premixed syngas combustion is the key to accomplish the MILD combustion of NH3. The impact of the temperature and O2 mole fraction of the HTDA on the emissions of NO, NO2, N2O, NH3, and CO was experimentally investigated with varying equivalence ratios and NH3 flow rates. The chemical reactor network was employed to analyze the experimental observation from the chemical kinetic aspect.

Ignition delay times (IDTs) of NH3/di-isopropyl ketone (DIPK) mixtures with DIPK fractions of 0%, 5%, 10%, and 50% were measured in a shock tube at pressures around 1.75 and 10bar, temperatures from 1300 to 2100 K, and an equivalence ratio of 0.5. A DIPK-NH3 model was proposed including the DIPK sub-model, NH3 sub-model, and reactions between nitrogen-containing species and hydrocarbon species. The proposed DIPK-NH3 model well predicts the IDTs measured in this study, and the IDT and laminar flame speed data of pure NH3 and pure DIPK reported in the literature. The reactions between nitrogen-containing species and hydrocarbon species consist of four reaction classes: (1) prompt NO and reburn mechanism; (2) recombination reactions and small amines mechanisms; (3) H-abstraction reactions; (4) disproportionation reactions. Reaction classes 1-4 were successively added into a combined NH3 and DIPK model. Comparison of the model predictions shows that the reaction class 1 and 2 have almost no influence on the ignition, while class 3 inhibits the ignition and class 4 significantly inhibits the ig-nition. The ignition inhibiting effects of class 3 mainly come from C3H6 + NH2 = C3H5-A + NH3 (R3032) at DIPK blending ratio of 5% and 10%, and C2H4 + NO = C2H3 + HNO (R3058) at DIPK blending ratio of 50% and 10 bar. The ignition inhibiting effects of class 4 mainly come from HCO + NH2= CO + NH3 (R3050), C2H3+ NH2= C2H2+ NH3 (R3047), and NH2+ C3H5-A = C3H4-A + NH3 (R3065) at DIPK blending ratio of 5% and 10%, and C3H5-A + NO = C3H4-A + HNO (R3067) at DIPK blending ratio of 50% and 10 bar. The NH3/DIPK oxidation pathway and effects of DIPK blending ratio on the IDT of NH3 were also analyzed in detail.& COPY; 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

NH3 can be used as an H-2 energy carrier or an alternative carbon-free fuel because of its high volumetric energy density and easy liquefaction, which leads to convenient and economic transportation and storage within the global energy network. However, the combustion of NH3 is associated with some practical challenges, such as weak reactivity and high NOx emission. In this study, Moderate & Intense Low Oxygen Dilution (MILD) combustion of NH3 was conducted experimentally in a novel burner. The heated and diluted air was produced by burning a premixed lean CH4 mixture using a metal fiber burner installed at the bottom of the combustion chamber and NH3 was injected into the furnace by 20 nozzles oppositely installed on the sidewalls of the combustion chamber at 40 mm above its bottom. A total of 20 cases were investigated in the present work, including premixed combustion of CH4 and CH4/NH3, and MILD combustion of NH3, under various conditions. The Chemical reactor network (CRN) in the ANSYS Chemkin 17.0 and the HUST mechanism were used to simulate and analyze the NO formation mechanism under several experimental conditions. The experimental results showed that the NH3 MILD combustion significantly reduces the NOx emissions. The NOx reduction kinetics and the impact of NH3 flow rate and the equivalence ratio on NO emission in NH3 MILD combustion were analyzed in detail.

The Dimethyl ether (DME) kinetic model is significant to understand the DME combustion in the atmosphere containing high CO2 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/CO2, O-2/N-2, O-2/N-2/He/CO2 and O-2/CO2. The OXYDME model was compared with OXY-Aramco, Liu-DME model in detail. The effects of CO2 on the DME ignition are very weak and not sensitive to the temperature and pressure. The reason for the weak effects of CO2 is that the chemical effects of CO2 promote ignition, which counteracts the inhibition effects caused by the physical properties of CO2. The chaperon effects of CO2 dominate the chemical effects. Meanwhile, the effects of the reactions with CO2 are very small. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.