Combustion and Flame最新文献_第10页

Triptane (2,2,3-trimethylbutane) as an Anti-Knock Additive in Renewable Gasoline: Experiments and Kinetic Modelling 雷公藤烷（2,2,3-三甲基丁烷）在可再生汽油中的抗爆添加剂：实验和动力学模型

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-06 DOI: 10.1016/j.combustflame.2025.114696

Khalid Aljohani , Aamir Farooq

Triptane (2,2,3-trimethylbutane), a highly branched paraffin with superior anti-knock properties, presents significant potential as an additive for enhancing the combustion characteristics of synthetic gasolines. Triptane can be selectively produced from methanol and dimethyl ether, offering a renewable route from bio- or e-derived feedstocks. This study investigates the autoignition behavior of neat triptane and the effect of adding 20 vol.% triptane in a methanol-to-gasoline fuel (MTG, RON 92.8). Ignition delay times (IDTs) were measured using a high-pressure shock tube (HPST) and a rapid compression machine (RCM). IDTs of neat triptane in air mixtures were measured over a temperature range of 970–1335 K, at pressures of 20 and 40 bar, and at equivalence ratios of φ = 0.5–1. The high-temperature IDTs complement literature low-temperature measurements (Atef et al. 2019) and show good agreement with kinetic modelling predictions. For MTG–triptane blend, IDTs were conducted across T = 660–1370 K, p = 10, 20, 30 bar, and at equivalence ratios of φ = 0.5–1. Results revealed a temperature-dependent dual behavior of triptane. At high temperatures (T > 970 K), triptane enhances MTG reactivity, shortening IDTs, whereas it exhibits an inhibitory effect in the intermediate temperature regime (730–940 K). At lower temperatures (T < 730 K), however, the blend consistently ignites faster than either neat component, highlighting complex underlying chemical interactions. A recently developed comprehensive gasoline kinetic model was integrated with a literature triptane sub-model comprising 29 reaction classes spanning both high- and low-temperature regimes. This composite model, along with triptane-containing surrogates developed in this study, was used to assess the impact of triptane blending on MTG reactivity. Brute-force IDT sensitivity analyses showed that the low-temperature reactivity of the triptane–MTG blend is mainly controlled by MTG-specific low-temperature chemistry. At intermediate temperatures, the observed inhibition effect is linked to the common controlling reactions of triptane and MTG. At high temperatures, the increased reactivity is primarily due to triptane-driven pathways. The combined of experimental and modeling study provide valuable insights into triptane’s perturbative effects, highlighting its promise for optimizing advanced low-carbon gasoline fuels.

Triptane（2,2,3-三甲基丁烷）是一种高度支化的石蜡，具有优异的抗爆性能，作为一种增强合成汽油燃烧特性的添加剂具有很大的潜力。Triptane可以选择性地从甲醇和二甲醚中生产，这为生物或电子衍生原料提供了可再生途径。本研究考察了纯triptane的自燃行为以及在甲醇-汽油燃料中添加20%的triptane的影响（MTG, RON 92.8）。采用高压激波管（HPST）和快速压缩机（RCM）测量点火延迟时间（IDTs）。在970-1335 K的温度范围内，在20和40 bar的压力下，在φ = 0.5-1的等效比下，测量了纯雷公藤烷在空气混合物中的IDTs。高温IDTs补充了文献中的低温测量（Atef et al. 2019），并与动力学模型预测显示出良好的一致性。对于MTG-triptane共混物，在T = 660-1370 K, p = 10, 20, 30 bar, φ = 0.5-1的等效比下进行IDTs。结果揭示了曲坦的温度依赖性双重行为。在高温（970 K）下，triptane增强MTG反应性，缩短idt，而在中温（730-940 K）下则表现出抑制作用。然而，在较低的温度下（730k），混合物始终比任何一种纯组分燃烧得更快，突出了复杂的潜在化学相互作用。一个最近开发的综合汽油动力学模型与文献中的triptane子模型相结合，包括29个反应类别，跨越高温和低温状态。该复合模型与本研究中开发的含曲坦替代品一起用于评估曲坦混合对MTG反应性的影响。蛮力IDT敏感性分析表明，曲坦- mtg共混物的低温反应性主要受mtg特异性低温化学控制。在中等温度下，观察到的抑制效果与雷公藤烷和MTG的常见控制反应有关，在高温下，反应活性的增加主要是由于雷公藤烷驱动的途径。实验和模型研究相结合，提供了有价值的见解，对triptane的扰动效应，突出其前景优化先进的低碳汽油燃料。

{"title":"Triptane (2,2,3-trimethylbutane) as an Anti-Knock Additive in Renewable Gasoline: Experiments and Kinetic Modelling","authors":"Khalid Aljohani , Aamir Farooq","doi":"10.1016/j.combustflame.2025.114696","DOIUrl":"10.1016/j.combustflame.2025.114696","url":null,"abstract":"<div><div>Triptane (2,2,3-trimethylbutane), a highly branched paraffin with superior anti-knock properties, presents significant potential as an additive for enhancing the combustion characteristics of synthetic gasolines. Triptane can be selectively produced from methanol and dimethyl ether, offering a renewable route from bio- or e-derived feedstocks. This study investigates the autoignition behavior of neat triptane and the effect of adding 20 vol.% triptane in a methanol-to-gasoline fuel (MTG, RON 92.8). Ignition delay times (IDTs) were measured using a high-pressure shock tube (HPST) and a rapid compression machine (RCM). IDTs of neat triptane in air mixtures were measured over a temperature range of 970–1335 K, at pressures of 20 and 40 bar, and at equivalence ratios of <em>φ</em> = 0.5–1. The high-temperature IDTs complement literature low-temperature measurements (Atef et al. 2019) and show good agreement with kinetic modelling predictions. For MTG–triptane blend, IDTs were conducted across <em>T</em> = 660–1370 K, <em>p</em> = 10, 20, 30 bar, and at equivalence ratios of <em>φ</em> = 0.5–1. Results revealed a temperature-dependent dual behavior of triptane. At high temperatures (<em>T</em> > 970 K), triptane enhances MTG reactivity, shortening IDTs, whereas it exhibits an inhibitory effect in the intermediate temperature regime (730–940 K). At lower temperatures (<em>T</em> < 730 K), however, the blend consistently ignites faster than either neat component, highlighting complex underlying chemical interactions. A recently developed comprehensive gasoline kinetic model was integrated with a literature triptane sub-model comprising 29 reaction classes spanning both high- and low-temperature regimes. This composite model, along with triptane-containing surrogates developed in this study, was used to assess the impact of triptane blending on MTG reactivity. Brute-force IDT sensitivity analyses showed that the low-temperature reactivity of the triptane–MTG blend is mainly controlled by MTG-specific low-temperature chemistry. At intermediate temperatures, the observed inhibition effect is linked to the common controlling reactions of triptane and MTG. At high temperatures, the increased reactivity is primarily due to triptane-driven pathways. The combined of experimental and modeling study provide valuable insights into triptane’s perturbative effects, highlighting its promise for optimizing advanced low-carbon gasoline fuels.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114696"},"PeriodicalIF":6.2,"publicationDate":"2025-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of PODE3 addition on chemistry of premixed burner-stabilized stagnation ethylene sooting flames: An experimental and numerical study 添加PODE3对预混合燃烧器稳定滞胀式乙烯烟尘火焰化学性质的影响：实验与数值研究

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-05 DOI: 10.1016/j.combustflame.2025.114684

Hang Ren , Yaoyao Ying , Kaixuan Yang , Runtian Yu , Chen Chen , Bingkun Wu , Danan Qi , Dong Liu

Effect of polyoxymethylene dimethyl ethers 3 (PODE₃) on soot precursor chemistry were investigated in premixed burner-stabilized stagnation flames. Spatial concentration distributions of important soot precursors in flames with varying PODE₃ doping levels were quantified. Comparative analyses were conducted between experimental data and numerical simulation results obtained from two kinetic mechanisms. Reaction pathway analyses and rate of production (ROP) evaluations were further performed to elucidate the chemical effects of PODE₃ on soot precursors. The experiment results found that PODE₃ suppressed soot formation in flames primarily through chemical effects rather than thermal effects. The concentrations of key soot precursors exhibited a monotonic decreasing trend with rising PODE₃ doping level. This could be attributed to PODE₃ reducing the C₂H₄ fuel source and introducing complex pathways. The dominant benzene formation pathways were found to differ between the pre-combustion region (the C3 pathway dominated) and the post-combustion region (the C4+C2 pathway dominated) in premixed burner-stabilized stagnation flames. PODE₃ addition suppressed both pathways. This study demonstrated how PODE₃ affected the soot precursors formation in premixed burner stabilized-stagnation flames, and provided data support for the practical application of PODE₃ and the improvement of relevant mechanisms.

研究了聚氧二甲基醚3 （PODE3）在预混合燃烧器稳定停滞火焰中对烟尘前驱体化学性质的影响。量化了不同PODE3掺杂水平下火焰中重要烟尘前体的空间浓度分布。对两种动力学机制的实验数据和数值模拟结果进行了对比分析。通过反应途径分析和ROP评价，进一步阐明了PODE3对煤烟前驱体的化学作用。实验结果发现，PODE3主要通过化学作用而非热效应抑制火焰中烟灰的形成。随着PODE3掺杂水平的升高，主要烟尘前体的浓度呈单调下降趋势。这可能归因于PODE3减少了C2H4燃料源并引入了复杂的途径。在燃烧器稳定的预混合滞火中，主要的苯生成途径在燃烧前区域（C3途径为主）和燃烧后区域（C4+C2途径为主）之间存在差异。PODE3的加入抑制了这两种途径。本研究揭示了PODE3对预混燃烧器稳滞火焰中煤烟前驱体形成的影响，为PODE3的实际应用及相关机理的完善提供了数据支持。

{"title":"Effect of PODE3 addition on chemistry of premixed burner-stabilized stagnation ethylene sooting flames: An experimental and numerical study","authors":"Hang Ren , Yaoyao Ying , Kaixuan Yang , Runtian Yu , Chen Chen , Bingkun Wu , Danan Qi , Dong Liu","doi":"10.1016/j.combustflame.2025.114684","DOIUrl":"10.1016/j.combustflame.2025.114684","url":null,"abstract":"<div><div>Effect of polyoxymethylene dimethyl ethers 3 (PODE<sub>3</sub>) on soot precursor chemistry were investigated in premixed burner-stabilized stagnation flames. Spatial concentration distributions of important soot precursors in flames with varying PODE<sub>3</sub> doping levels were quantified. Comparative analyses were conducted between experimental data and numerical simulation results obtained from two kinetic mechanisms. Reaction pathway analyses and rate of production (ROP) evaluations were further performed to elucidate the chemical effects of PODE<sub>3</sub> on soot precursors. The experiment results found that PODE<sub>3</sub> suppressed soot formation in flames primarily through chemical effects rather than thermal effects. The concentrations of key soot precursors exhibited a monotonic decreasing trend with rising PODE<sub>3</sub> doping level. This could be attributed to PODE<sub>3</sub> reducing the C<sub>2</sub>H<sub>4</sub> fuel source and introducing complex pathways. The dominant benzene formation pathways were found to differ between the pre-combustion region (the C3 pathway dominated) and the post-combustion region (the C4+C2 pathway dominated) in premixed burner-stabilized stagnation flames. PODE<sub>3</sub> addition suppressed both pathways. This study demonstrated how PODE<sub>3</sub> affected the soot precursors formation in premixed burner stabilized-stagnation flames, and provided data support for the practical application of PODE<sub>3</sub> and the improvement of relevant mechanisms.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114684"},"PeriodicalIF":6.2,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Understanding key parameters enhancing performance of iron powder combustion in a semi-practical burner 了解在半实用燃烧器中提高铁粉燃烧性能的关键参数

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-05 DOI: 10.1016/j.combustflame.2025.114693

Willie Prasidha , Mohammadreza Baigmohammadi , Yuriy Shoshin , Philip de Goey

This work investigates the combustion of micron-sized iron powder as an energy storage medium using the semi-practical Metal Cyclonic Combustor (MC²). It evaluates the effects of preheating temperature, power output, water vapor content, and swirling flow on flame characteristics, combustion efficiency, gas temperature, residue composition, and NO emissions. A preheating temperature of 760°C yields an oxidation degree of 90 wt% without external heat support, although the flame is non-stationary. At 810°C, the flame becomes stationary and more stable, with higher oxidation degree and gas temperature. Increasing the iron powder injection rate enhances power output and gas temperature but requires burner modifications for sustained efficiency. Water vapor decreases the degree of oxidation, increases the amount of unburned iron, and lowers particle and gas temperatures, while contributing to NO formation. However, excessive vapor reduces NO emissions by absorbing heat and lowering the gas temperature. Swirling flow improves combustion efficiency, stabilizes the flame, and reduces unburned iron. Under fuel-lean conditions, it facilitates the transition to a stationary self-sustaining flame. These findings support the feasibility of iron powder as an efficient energy carrier and advance iron-based combustion technology for sustainable energy systems.

Novelty and significance statement

This work investigates the combustion behavior of micron-sized iron powder using a semi-practical burner, focusing on its potential as a clean energy carrier. It analyzes iron flame characteristics, combustion residue composition, oxidation, efficiency, particle and gas temperatures, and NO emissions under varying conditions. Unlike previous single-particle combustion works, this work explores continuous combustion at a larger scale, identifying key parameters for stable, self-sustaining iron flames without heat support. The findings provide practical methods to enhance flame stability in real-world conditions, supporting iron powder as an efficient, clean energy system.

本文利用半实用的金属旋风燃烧器（MC2）研究了微米级铁粉作为储能介质的燃烧。它评估了预热温度、功率输出、水蒸气含量和旋转流量对火焰特性、燃烧效率、气体温度、残留物组成和NO排放的影响。在没有外部热支持的情况下，760°C的预热温度产生90 wt%的氧化度，尽管火焰是不稳定的。在810℃时，火焰变得平稳，更加稳定，氧化度和气体温度更高。增加铁粉喷射速度可以提高功率输出和气体温度，但需要修改燃烧器以保持效率。水蒸气降低氧化程度，增加未燃烧铁的数量，降低颗粒和气体温度，同时促进NO的形成。然而，过量的蒸汽通过吸收热量和降低气体温度来减少NO的排放。旋流提高燃烧效率，稳定火焰，减少未燃铁。在燃料稀薄的条件下，它有助于过渡到静止的自持火焰。这些发现支持了铁粉作为高效能量载体的可行性，并推动了可持续能源系统中铁基燃烧技术的发展。新颖性和意义声明本工作研究了微米级铁粉在半实用燃烧器上的燃烧行为，重点研究了其作为清洁能源载体的潜力。它分析了不同条件下的铁火焰特性、燃烧残渣成分、氧化、效率、颗粒和气体温度以及NO排放。与以往的单颗粒燃烧工作不同，这项工作探索了更大规模的连续燃烧，确定了在没有热支持的情况下稳定、自我维持的铁火焰的关键参数。研究结果提供了实用的方法，以提高在现实条件下的火焰稳定性，支持铁粉作为一个高效，清洁的能源系统。

{"title":"Understanding key parameters enhancing performance of iron powder combustion in a semi-practical burner","authors":"Willie Prasidha , Mohammadreza Baigmohammadi , Yuriy Shoshin , Philip de Goey","doi":"10.1016/j.combustflame.2025.114693","DOIUrl":"10.1016/j.combustflame.2025.114693","url":null,"abstract":"<div><div>This work investigates the combustion of micron-sized iron powder as an energy storage medium using the semi-practical Metal Cyclonic Combustor (MC<sup>2</sup>). It evaluates the effects of preheating temperature, power output, water vapor content, and swirling flow on flame characteristics, combustion efficiency, gas temperature, residue composition, and NO emissions. A preheating temperature of 760°C yields an oxidation degree of 90 wt% without external heat support, although the flame is non-stationary. At 810°C, the flame becomes stationary and more stable, with higher oxidation degree and gas temperature. Increasing the iron powder injection rate enhances power output and gas temperature but requires burner modifications for sustained efficiency. Water vapor decreases the degree of oxidation, increases the amount of unburned iron, and lowers particle and gas temperatures, while contributing to NO formation. However, excessive vapor reduces NO emissions by absorbing heat and lowering the gas temperature. Swirling flow improves combustion efficiency, stabilizes the flame, and reduces unburned iron. Under fuel-lean conditions, it facilitates the transition to a stationary self-sustaining flame. These findings support the feasibility of iron powder as an efficient energy carrier and advance iron-based combustion technology for sustainable energy systems.</div></div><div><h3>Novelty and significance statement</h3><div>This work investigates the combustion behavior of micron-sized iron powder using a semi-practical burner, focusing on its potential as a clean energy carrier. It analyzes iron flame characteristics, combustion residue composition, oxidation, efficiency, particle and gas temperatures, and NO emissions under varying conditions. Unlike previous single-particle combustion works, this work explores continuous combustion at a larger scale, identifying key parameters for stable, self-sustaining iron flames without heat support. The findings provide practical methods to enhance flame stability in real-world conditions, supporting iron powder as an efficient, clean energy system.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114693"},"PeriodicalIF":6.2,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Thermal expansion-driven laser ignition in a gas subscale rocket combustor 气体亚尺度火箭燃烧室中热膨胀驱动激光点火

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-04 DOI: 10.1016/j.combustflame.2025.114692

Davy Brouzet , Diego Rossinelli , Tony Zahtila , Alboreno Voci , Ryan Strelau , Alexander Warner , Rohan M. Gejji , Carson D. Slabaugh , Gianluca Iaccarino

Laser ignition of rocket propellants offers significant advantages over conventional ignition systems, including reduced weight and improved reliability. However, the complex multi-physics processes governing ignition remain poorly understood, particularly regarding the role of thermal expansion effects. This study combines high-fidelity large-eddy simulations (LES) with experimental validation to investigate the mechanisms controlling laser ignition success in a subscale model rocket combustor using gaseous methane and oxygen as propellants. Novel numerical schlieren and chemiluminescence imaging techniques based on physics-based principles are developed to enable direct comparison with experimental data. Four ignition scenarios with varying fuel mass flow rates are examined, ranging from immediate flame quenching to rapid flame anchoring. The LES accurately reproduces experimental pressure traces, schlieren imaging, and chemiluminescence patterns, validating the computational approach. Results demonstrate that successful ignition depends critically on thermal expansion effects rather than traditional turbulent flame propagation mechanisms. When sufficient fuel is present in the chamber, thermal expansion generates upstream flow velocities that enable flame kernel propagation against the high-velocity jet flow and subsequent anchoring at the combustor inlet. The study reveals an optimal fuel concentration range that ensures reliable ignition while limiting structural overpressure, providing practical guidelines for rocket engine design. These findings challenge conventional understanding of rocket ignition mechanisms and offer new pathways for developing lighter, safer, and more reliable propulsion systems.

Novelty and significance

This study presents a paradigm shift in understanding rocket ignition mechanisms by demonstrating that thermal expansion effects arising from sudden consumption of reactants, rather than traditional turbulent flame propagation, can govern successful laser ignition in gas rocket combustors. The study challenges the conventional understanding that requires flammable mixtures in recirculation zones for ignition success. Consequently, lower fuel amounts inside the combustor can be used to reduce the overpressure without jeopardizing ignition outcome. These findings offer new design pathways for propulsion systems by leveraging thermal expansion mechanisms rather than relying on excessive reactant buildup, providing practical guidelines for developing lighter and safer rocket engines.

与传统点火系统相比，激光点火火箭推进剂具有显著的优势，包括减轻重量和提高可靠性。然而，控制点火的复杂多物理过程仍然知之甚少，特别是关于热膨胀效应的作用。本研究将高保真大涡模拟（LES）与实验验证相结合，研究了以气态甲烷和氧气为推进剂的亚尺度模型火箭燃烧室中激光点火成功的控制机制。基于物理原理的新型数值纹影和化学发光成像技术得以发展，从而能够与实验数据进行直接比较。研究了四种不同燃料质量流量的点火场景，从立即火焰熄灭到快速火焰锚定。LES精确地再现了实验压力痕迹、纹影成像和化学发光模式，验证了计算方法。结果表明，成功点火关键取决于热膨胀效应，而不是传统的湍流火焰传播机制。当燃烧室中有足够的燃料时，热膨胀产生上游流动速度，使火焰核能够在高速射流中传播并随后在燃烧室入口锚定。该研究揭示了在保证可靠点火的同时限制结构超压的最佳燃料浓度范围，为火箭发动机设计提供了实用指导。这些发现挑战了对火箭点火机制的传统理解，并为开发更轻、更安全、更可靠的推进系统提供了新的途径。本研究通过证明由反应物的突然消耗而不是传统的湍流火焰传播引起的热膨胀效应可以控制燃气火箭燃烧室中成功的激光点火，从而展示了理解火箭点火机制的范式转变。该研究挑战了传统的理解，即需要在再循环区域中使用可燃混合物才能成功点火。因此，较低的燃料量内的燃烧器可以用来减少超压而不危及点火结果。这些发现为利用热膨胀机制而不是依赖过多反应物的推进系统提供了新的设计途径，为开发更轻、更安全的火箭发动机提供了实用指导。

{"title":"Thermal expansion-driven laser ignition in a gas subscale rocket combustor","authors":"Davy Brouzet , Diego Rossinelli , Tony Zahtila , Alboreno Voci , Ryan Strelau , Alexander Warner , Rohan M. Gejji , Carson D. Slabaugh , Gianluca Iaccarino","doi":"10.1016/j.combustflame.2025.114692","DOIUrl":"10.1016/j.combustflame.2025.114692","url":null,"abstract":"<div><div>Laser ignition of rocket propellants offers significant advantages over conventional ignition systems, including reduced weight and improved reliability. However, the complex multi-physics processes governing ignition remain poorly understood, particularly regarding the role of thermal expansion effects. This study combines high-fidelity large-eddy simulations (LES) with experimental validation to investigate the mechanisms controlling laser ignition success in a subscale model rocket combustor using gaseous methane and oxygen as propellants. Novel numerical schlieren and chemiluminescence imaging techniques based on physics-based principles are developed to enable direct comparison with experimental data. Four ignition scenarios with varying fuel mass flow rates are examined, ranging from immediate flame quenching to rapid flame anchoring. The LES accurately reproduces experimental pressure traces, schlieren imaging, and chemiluminescence patterns, validating the computational approach. Results demonstrate that successful ignition depends critically on thermal expansion effects rather than traditional turbulent flame propagation mechanisms. When sufficient fuel is present in the chamber, thermal expansion generates upstream flow velocities that enable flame kernel propagation against the high-velocity jet flow and subsequent anchoring at the combustor inlet. The study reveals an optimal fuel concentration range that ensures reliable ignition while limiting structural overpressure, providing practical guidelines for rocket engine design. These findings challenge conventional understanding of rocket ignition mechanisms and offer new pathways for developing lighter, safer, and more reliable propulsion systems.</div><div><strong>Novelty and significance</strong></div><div>This study presents a paradigm shift in understanding rocket ignition mechanisms by demonstrating that thermal expansion effects arising from sudden consumption of reactants, rather than traditional turbulent flame propagation, can govern successful laser ignition in gas rocket combustors. The study challenges the conventional understanding that requires flammable mixtures in recirculation zones for ignition success. Consequently, lower fuel amounts inside the combustor can be used to reduce the overpressure without jeopardizing ignition outcome. These findings offer new design pathways for propulsion systems by leveraging thermal expansion mechanisms rather than relying on excessive reactant buildup, providing practical guidelines for developing lighter and safer rocket engines.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114692"},"PeriodicalIF":6.2,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Laminar burning velocities of toluene, TRF, and PRF flames: More reliable datasets for model validations including ultra-lean conditions 甲苯、TRF和PRF火焰的层流燃烧速度：更可靠的模型验证数据集，包括超稀薄条件

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-04 DOI: 10.1016/j.combustflame.2025.114691

Xinlu Han , Leilei Xu , Yong Qian

Toluene is a representative aromatic component in gasoline surrogates, and its combustion characteristics have arisen significant research interest. However, the laminar burning velocity of toluene, a paramount fundamental combustion property, shows significant data scatterings among available literature studies, where there also lacks the data under the very lean conditions. In the present study, the laminar burning velocities of toluene flames, together with toluene reference fuel (TRF), and primary reference fuel (PRF) flames, were measured at 1 atm and 298 K using the heat flux method. The experiments included ultra-lean conditions with equivalence ratio as low as 0.5, which was achieved through oxygen enrichment. Extrapolation using a validated linear model was adopted for the lean fuel+air laminar burning velocities that can’t be measured directly. Together with the present data, all the available 1 atm toluene+air data were collected in literature, and more reliable datasets for model validations were suggested based on comprehensive data consistency analyses. This process was also applied to benzene+air flames, as benzene is an important intermediate species during toluene combustion and an individual fuel. Two widely used detailed models for gasoline surrogates, from LLNL and CRECK, were assessed using the suggested datasets, where noticeable deviations were found for both models. A reduced toluene subset was also proposed in the present study, combined with the former model from the authors, yielding a compact model with lower deviations across all conditions. Beside the experiments and simulations, global flame characteristics and reaction sensitivities were analysed, revealing toluene flames to be more stable and robust, contrasting with isooctane, n-heptane, and PRF flames, which doesn’t have noises in the ultra-lean measurements that associated with pulsating flame instabilities. The importance of cyclic-carbon reactions on laminar burning velocities under the various equivalence ratio conditions was also highlighted, different from the isooctane, n-heptane, and PRF flames that are governing mostly by the H2/C1 reactions especially under the ultra-lean conditions.

甲苯是汽油代用品中具有代表性的芳香族成分，其燃烧特性引起了人们的广泛关注。然而，甲苯的层流燃烧速度这一最重要的基本燃烧特性，在现有文献研究中显示出明显的数据分散，在非常稀薄的条件下也缺乏数据。本研究采用热流密度法测量了甲苯火焰与甲苯基准燃料（TRF）和一次基准燃料（PRF）火焰在1atm和298 K下的层流燃烧速度。实验采用超贫条件，等效比低至0.5，通过富氧实现。对于无法直接测量的稀薄燃料+空气层流燃烧速度，采用验证的线性模型进行外推。结合本数据，收集文献中所有可获得的1 atm甲苯+空气数据，并在综合数据一致性分析的基础上，提出更可靠的模型验证数据集。该方法也适用于苯+空气火焰，因为苯是甲苯燃烧过程中重要的中间物质，也是一种单独的燃料。使用建议的数据集对来自LLNL和CRECK的两个广泛使用的汽油替代品详细模型进行了评估，发现两个模型都存在明显的偏差。在本研究中还提出了一个减少的甲苯子集，与作者的前模型相结合，产生一个紧凑的模型，在所有条件下都具有较低的偏差。除了实验和模拟之外，还分析了整体火焰特性和反应灵敏度，揭示了甲苯火焰比异辛烷，正庚烷和PRF火焰更稳定和强大，而异辛烷，正庚烷和PRF火焰在超精益测量中没有与脉动火焰不稳定性相关的噪音。不同于异辛烷、正庚烷和PRF火焰主要由H2/C1反应控制，特别是在超稀薄条件下，循环碳反应对层流燃烧速度的影响也得到了突出的体现。

{"title":"Laminar burning velocities of toluene, TRF, and PRF flames: More reliable datasets for model validations including ultra-lean conditions","authors":"Xinlu Han , Leilei Xu , Yong Qian","doi":"10.1016/j.combustflame.2025.114691","DOIUrl":"10.1016/j.combustflame.2025.114691","url":null,"abstract":"<div><div>Toluene is a representative aromatic component in gasoline surrogates, and its combustion characteristics have arisen significant research interest. However, the laminar burning velocity of toluene, a paramount fundamental combustion property, shows significant data scatterings among available literature studies, where there also lacks the data under the very lean conditions. In the present study, the laminar burning velocities of toluene flames, together with toluene reference fuel (TRF), and primary reference fuel (PRF) flames, were measured at 1 atm and 298 K using the heat flux method. The experiments included ultra-lean conditions with equivalence ratio as low as 0.5, which was achieved through oxygen enrichment. Extrapolation using a validated linear model was adopted for the lean fuel+air laminar burning velocities that can’t be measured directly. Together with the present data, all the available 1 atm toluene+air data were collected in literature, and more reliable datasets for model validations were suggested based on comprehensive data consistency analyses. This process was also applied to benzene+air flames, as benzene is an important intermediate species during toluene combustion and an individual fuel. Two widely used detailed models for gasoline surrogates, from LLNL and CRECK, were assessed using the suggested datasets, where noticeable deviations were found for both models. A reduced toluene subset was also proposed in the present study, combined with the former model from the authors, yielding a compact model with lower deviations across all conditions. Beside the experiments and simulations, global flame characteristics and reaction sensitivities were analysed, revealing toluene flames to be more stable and robust, contrasting with isooctane, n-heptane, and PRF flames, which doesn’t have noises in the ultra-lean measurements that associated with pulsating flame instabilities. The importance of cyclic-carbon reactions on laminar burning velocities under the various equivalence ratio conditions was also highlighted, different from the isooctane, n-heptane, and PRF flames that are governing mostly by the H2/C1 reactions especially under the ultra-lean conditions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114691"},"PeriodicalIF":6.2,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Impact of NO on soot oxidation under gasoline direct injection engines exhaust condition 汽油直喷发动机排气条件下NO对烟尘氧化的影响

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-03 DOI: 10.1016/j.combustflame.2025.114688

Xiangyu Dong , Yu Lyu , Xuyang Zhang , Ruibin Sun , Gang Lyu , Chonglin Song

The oxidation of soot under gasoline direct injection (GDI) engines exhaust conditions plays a critical role in particulate emission control. However, the impact of nitric oxide (NO) on this process remains insufficiently understood. This study combines experimental characterization, density functional theory (DFT) calculations, and kinetic simulations to investigate the inhibitory effect of NO on soot oxidation. Compared to oxidation in O₂ alone, the presence of NO suppresses oxidation by occupying active sites and blocking the reaction between O₂ and soot. This site-blocking effect leads to reduced oxidation reactivity and noticeable changes in soot properties, including decreased surface oxygen content and inhibited graphitization. Online mass spectrometry reveals increased O₂ signal upon NO introduction, confirming site-blocking behavior. DFT calculations indicate that NO tends to form C(NO) species following adsorption, which are kinetically unfavorable for further oxidation due to their high activation barriers. Combined with kinetic simulations, the calculation results further support that C(NO) occupies active sites, preventing access by more reactive O₂—consistent with the observed increase in O₂ concentration and the decrease in surface oxygen content in the presence of NO The reversibility of NO inhibition is attributed to the rapid decomposition of C(NO), which can release NO and restore active sites.

Novelty and significance statement The novelty of this study lies in unveiling the inhibitory effect of NO on soot oxidation under GDI engine exhaust condition. It provides a comprehensive understanding of the inhibition mechanism by combining experimental analyses of soot physicochemical properties with theoretical calculations. This work is significant in advancing the fundamental understanding of oxidation reactions in carbonaceous materials and offers theoretical insights for developing emission reduction strategies.

在汽油直喷发动机排气工况下，油烟的氧化对控制颗粒排放起着至关重要的作用。然而，一氧化氮（NO）对这一过程的影响仍未得到充分的了解。本研究结合实验表征、密度泛函理论（DFT）计算和动力学模拟来研究NO对烟尘氧化的抑制作用。与单独在O2中氧化相比，NO的存在通过占据活性位点和阻断O2与烟灰之间的反应来抑制氧化。这种位点阻断效应导致氧化反应性降低，烟灰性质发生明显变化，包括表面氧含量降低和石墨化抑制。在线质谱分析显示，引入NO后O2信号增加，证实了位点阻断行为。DFT计算表明，吸附后NO倾向于形成C(NO)，由于其高活化障碍，在动力学上不利于进一步氧化。结合动力学模拟，计算结果进一步支持C（NO）占据活性位点，阻止更多的活性氧进入，这与观察到的NO存在时O2浓度升高和表面氧含量降低相一致。NO抑制的可逆性归因于C（NO）的快速分解，释放NO，恢复活性位点。本研究的新颖之处在于揭示了GDI发动机排气条件下NO对烟尘氧化的抑制作用。通过对煤烟理化性质的实验分析与理论计算相结合，对煤烟的抑制机理有了全面的认识。这项工作在推进对碳质材料氧化反应的基本认识方面具有重要意义，并为制定减排策略提供了理论见解。

{"title":"Impact of NO on soot oxidation under gasoline direct injection engines exhaust condition","authors":"Xiangyu Dong , Yu Lyu , Xuyang Zhang , Ruibin Sun , Gang Lyu , Chonglin Song","doi":"10.1016/j.combustflame.2025.114688","DOIUrl":"10.1016/j.combustflame.2025.114688","url":null,"abstract":"<div><div>The oxidation of soot under gasoline direct injection (GDI) engines exhaust conditions plays a critical role in particulate emission control. However, the impact of nitric oxide (NO) on this process remains insufficiently understood. This study combines experimental characterization, density functional theory (DFT) calculations, and kinetic simulations to investigate the inhibitory effect of NO on soot oxidation. Compared to oxidation in O<sub>2</sub> alone, the presence of NO suppresses oxidation by occupying active sites and blocking the reaction between O<sub>2</sub> and soot. This site-blocking effect leads to reduced oxidation reactivity and noticeable changes in soot properties, including decreased surface oxygen content and inhibited graphitization. Online mass spectrometry reveals increased O<sub>2</sub> signal upon NO introduction, confirming site-blocking behavior. DFT calculations indicate that NO tends to form C(NO) species following adsorption, which are kinetically unfavorable for further oxidation due to their high activation barriers. Combined with kinetic simulations, the calculation results further support that C(NO) occupies active sites, preventing access by more reactive O<sub>2</sub>—consistent with the observed increase in O<sub>2</sub> concentration and the decrease in surface oxygen content in the presence of NO The reversibility of NO inhibition is attributed to the rapid decomposition of C(NO), which can release NO and restore active sites.</div><div><strong>Novelty and significance statement</strong> The novelty of this study lies in unveiling the inhibitory effect of NO on soot oxidation under GDI engine exhaust condition. It provides a comprehensive understanding of the inhibition mechanism by combining experimental analyses of soot physicochemical properties with theoretical calculations. This work is significant in advancing the fundamental understanding of oxidation reactions in carbonaceous materials and offers theoretical insights for developing emission reduction strategies.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114688"},"PeriodicalIF":6.2,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A methodology to evaluate plasma-produced radical effects on flame enhancement 一种评价等离子体产生的自由基对火焰增强作用的方法

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-03 DOI: 10.1016/j.combustflame.2025.114698

Nicolas Barléon, Omar Dounia

<div><div>Plasma-assisted combustion is increasingly studied for addressing challenges such as ignition and flame stabilization. Studies using detailed kinetics in zero-dimensional reactors show that Nanosecond Repetitively Pulsed (NRP) discharges enhance ignition through ultra-fast production of active particles, outperforming thermal energy deposition. However, the plasma effects on flame properties, such as laminar flame speed and thickness, have not been studied much. Most numerical studies on flame speed enhancement rely on perturbing the inlet conditions of one-dimensional freely propagating flames based on zero-dimensional plasma-combustion reactor outputs, but this can violate frozen-state assumptions in fresh gases and ignore residence time effects. This study introduces a novel methodology for evaluating flame speed enhancement by NRP discharges, focusing on radical production. Inert species A<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span> that mimic plasma produced radicals are artificially introduced at the inlet of the flame. Then, these species are relaxed as A<span><math><mrow><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup><mo>⟶</mo></mrow></math></span> A following an Arrhenius-based rate <span><math><mrow><mi>k</mi><mo>=</mo><msubsup><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup><mo>exp</mo><mrow><mo>(</mo><mo>−</mo><msub><mrow><mi>E</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>/</mo><mi>R</mi><mi>T</mi><mo>)</mo></mrow></mrow></math></span> with <span><math><msubsup><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span> the characteristic relaxation timescale, allowing to control the location of the effective chemical energy deposition with two limiting cases: (i) <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>→</mo><mn>0</mn></mrow></math></span> and (ii) <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>→</mo><mi>∞</mi></mrow></math></span>, respectively corresponding to the inlet active radical injection and purely inert radical injection. The methodology has been applied to H<sub>2</sub>-air flames without lack of generality. Non-monotonic response of the flame speed enhancement with respect to the effective active radical production is observed in the phase space, allowing to highlight optimal radical production location within the flame, as well as evaluating individual radical H and O effectiveness at various equivalence ratios. Radical efficiency has been evaluated by comparison with thermal energy, showing increase of up to 20% of the mass flow rate. The proposed approach provides a versatile framework applicable to various mixtures, facilitating the analysis of laminar flame responses to active radical production in plasma-assisted combustion systems.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty o

等离子体辅助燃烧在解决诸如点火和火焰稳定等挑战方面的研究越来越多。在零维反应器中进行的详细动力学研究表明，纳秒重复脉冲（NRP）放电通过超快产生活性粒子来增强点火，优于热能沉积。然而，等离子体对层流火焰速度和厚度等火焰特性的影响研究较少。大多数关于火焰速度增强的数值研究依赖于基于零维等离子体燃烧反应器输出扰动一维自由传播火焰的入口条件，但这可能违反新鲜气体中的冻结状态假设，并且忽略了停留时间效应。本研究介绍了一种新的方法来评估NRP放电对火焰速度的增强，重点是自由基的产生。模拟等离子体产生的自由基的惰性物质A *被人为地引入火焰的入口。然后，这些物质按照Arrhenius-based速率k=τr−1exp(−Ea/RT) （τr−1为特征弛豫时间标度）松弛为A * * * A，允许在两个极限情况下控制有效化学能沉积的位置：(i) τr→0和(ii) τr→∞，分别对应于入口活性自由基注入和纯惰性自由基注入。该方法已应用于h2 -空气火焰而不缺乏通用性。在相空间中观察到火焰速度增强对有效活性自由基产生的非单调响应，从而可以突出火焰中最佳自由基产生位置，以及评估不同等效比下单个自由基H和O的有效性。通过与热能的比较，对自由基效率进行了评估，表明提高了高达20%的质量流量。提出的方法提供了一个适用于各种混合物的通用框架，便于分析等离子体辅助燃烧系统中活性自由基产生的层流火焰响应。新颖性和意义声明本研究的新颖性在于发展了一种数值方法来分析等离子体放电产生自由基对一维无应变预混火焰的影响，这一主题迄今为止受到的关注有限。这种新方法依赖于热控制等离子体自由基沉积，从而解决了与经典入口摄动方法相关的反应性入口问题，并允许控制能量沉积位置。所提出的方法简单，可以很容易地集成到任何火焰模拟代码。最后，将其应用于h2 -空气火焰，揭示了相空间中等离子体诱导化学效应最有效的区域。

{"title":"A methodology to evaluate plasma-produced radical effects on flame enhancement","authors":"Nicolas Barléon, Omar Dounia","doi":"10.1016/j.combustflame.2025.114698","DOIUrl":"10.1016/j.combustflame.2025.114698","url":null,"abstract":"<div><div>Plasma-assisted combustion is increasingly studied for addressing challenges such as ignition and flame stabilization. Studies using detailed kinetics in zero-dimensional reactors show that Nanosecond Repetitively Pulsed (NRP) discharges enhance ignition through ultra-fast production of active particles, outperforming thermal energy deposition. However, the plasma effects on flame properties, such as laminar flame speed and thickness, have not been studied much. Most numerical studies on flame speed enhancement rely on perturbing the inlet conditions of one-dimensional freely propagating flames based on zero-dimensional plasma-combustion reactor outputs, but this can violate frozen-state assumptions in fresh gases and ignore residence time effects. This study introduces a novel methodology for evaluating flame speed enhancement by NRP discharges, focusing on radical production. Inert species A<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span> that mimic plasma produced radicals are artificially introduced at the inlet of the flame. Then, these species are relaxed as A<span><math><mrow><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup><mo>⟶</mo></mrow></math></span> A following an Arrhenius-based rate <span><math><mrow><mi>k</mi><mo>=</mo><msubsup><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup><mo>exp</mo><mrow><mo>(</mo><mo>−</mo><msub><mrow><mi>E</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>/</mo><mi>R</mi><mi>T</mi><mo>)</mo></mrow></mrow></math></span> with <span><math><msubsup><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math></span> the characteristic relaxation timescale, allowing to control the location of the effective chemical energy deposition with two limiting cases: (i) <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>→</mo><mn>0</mn></mrow></math></span> and (ii) <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>→</mo><mi>∞</mi></mrow></math></span>, respectively corresponding to the inlet active radical injection and purely inert radical injection. The methodology has been applied to H<sub>2</sub>-air flames without lack of generality. Non-monotonic response of the flame speed enhancement with respect to the effective active radical production is observed in the phase space, allowing to highlight optimal radical production location within the flame, as well as evaluating individual radical H and O effectiveness at various equivalence ratios. Radical efficiency has been evaluated by comparison with thermal energy, showing increase of up to 20% of the mass flow rate. The proposed approach provides a versatile framework applicable to various mixtures, facilitating the analysis of laminar flame responses to active radical production in plasma-assisted combustion systems.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty o","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114698"},"PeriodicalIF":6.2,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Investigations on the cook-off response of GAP-based propellant under solid rocket motor structural constraints 固体火箭发动机结构约束下gap基推进剂燃尽响应研究

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-03 DOI: 10.1016/j.combustflame.2025.114683

Yi Wu , Songlin Guo , Xingyuan Wang , Kangyu Ji , Qianlong Wang , Mi Yan

GAP-based high-energy solid propellants are prone to ignition and explosion under accidental thermal stimuli during storage and use. This study investigates the cook-off response characteristics of GAP-based propellant under solid rocket motor structural constraints. A motor-representative experimental specimen that incorporates the structural constraints of a rocket motor was employed to conduct cook-off experiments. The complete response process of the propellant under motor-constrained conditions, i.e. from initial heating to final explosion, was captured using a high-speed laser schlieren imaging system. The study reveals that the GAP propellant-based motor response can be divided into several distinct stages: preheating, pyrolysis and gas generation, melting, ignition, convection combustion and potential deflagration-to-detonation transition (DDT). Furthermore, the influences of factors such as nozzle diameter, casing thickness, and heating flux density on the cook-off response behaviour were comprehensively investigated. Moreover, a two-dimensional transient numerical simulation model was developed, capable of representing the thermal decomposition, phase transition, ignition and rapid pressure rise processes of GAP-based propellant under thermal loading. The simulation results were validated against experimental data, showing <2 % deviation in ignition delay time and approximately 0.7 % difference in peak shock wave overpressure, demonstrating satisfactory predictive accuracy.

基于间隙的高能固体推进剂在贮存和使用过程中容易受到意外热刺激而着火爆炸。研究了固体火箭发动机结构约束下gap基推进剂的燃尽响应特性。采用具有发动机代表性的实验试样，结合火箭发动机的结构约束，进行了点火实验。利用高速激光纹影成像系统捕获了推进剂在马达约束条件下从初始加热到最终爆炸的完整响应过程。研究表明，基于GAP推进剂的发动机响应可分为几个不同的阶段：预热、热解和产气、熔化、点火、对流燃烧和潜在爆燃-爆轰过渡（DDT）。此外，还研究了喷嘴直径、套管厚度、热流密度等因素对烧退响应特性的影响。建立了二维瞬态数值模拟模型，能够表征热载荷作用下gap基推进剂的热分解、相变、点火和快速升压过程。仿真结果与实验数据进行了对比，结果显示点火延迟时间偏差约为2%，冲击波超压峰值偏差约为0.7%，预测精度令人满意。

{"title":"Investigations on the cook-off response of GAP-based propellant under solid rocket motor structural constraints","authors":"Yi Wu , Songlin Guo , Xingyuan Wang , Kangyu Ji , Qianlong Wang , Mi Yan","doi":"10.1016/j.combustflame.2025.114683","DOIUrl":"10.1016/j.combustflame.2025.114683","url":null,"abstract":"<div><div>GAP-based high-energy solid propellants are prone to ignition and explosion under accidental thermal stimuli during storage and use. This study investigates the cook-off response characteristics of GAP-based propellant under solid rocket motor structural constraints. A motor-representative experimental specimen that incorporates the structural constraints of a rocket motor was employed to conduct cook-off experiments. The complete response process of the propellant under motor-constrained conditions, i.e. from initial heating to final explosion, was captured using a high-speed laser schlieren imaging system. The study reveals that the GAP propellant-based motor response can be divided into several distinct stages: preheating, pyrolysis and gas generation, melting, ignition, convection combustion and potential deflagration-to-detonation transition (DDT). Furthermore, the influences of factors such as nozzle diameter, casing thickness, and heating flux density on the cook-off response behaviour were comprehensively investigated. Moreover, a two-dimensional transient numerical simulation model was developed, capable of representing the thermal decomposition, phase transition, ignition and rapid pressure rise processes of GAP-based propellant under thermal loading. The simulation results were validated against experimental data, showing <2 % deviation in ignition delay time and approximately 0.7 % difference in peak shock wave overpressure, demonstrating satisfactory predictive accuracy.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114683"},"PeriodicalIF":6.2,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The influence of MILD-to-flame transition on stabilization, reactive structures, and emissions of NH3/H2 mixtures in a semi-industrial furnace 半工业炉中轻火过渡对NH3/H2混合物稳定性、反应结构和排放的影响

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-03 DOI: 10.1016/j.combustflame.2025.114687

Ebrahim Rahmani , Natalia Cid , M․Mustafa Kamal , Axel Coussement , Alessandro Parente , Marco Lubrano Lavadera

Ammonia (NH₃) is a promising carbon-free fuel for decarbonizing energy systems, but its use in practical combustion systems is hindered by low flame stability and NOₓ emissions. Burning NH₃ with hydrogen (H₂) has been proposed to improve stability in conventional combustion systems; however, NOₓ emissions may persist or worsen. Moderate or Intense Low-Oxygen Dilution (MILD) combustion offers a pathway to suppress NOₓ through distributed reaction zones and reduced peak temperatures. The aim of this study is to stabilize pure NH₃ and characterize it with the H₂ addition in a semi-industrial reverse-flow furnace under MILD conditions. The experiments demonstrated the stabilization of pure NH₃ under MILD conditions without reactive enhancers, resulting in negligible NOₓ emissions but significant NH₃ slip. The impact of H₂ addition was assessed by analyzing how the transition from MILD to flame influences emissions. A transition from MILD to a lifted flame occurred at ∼14 % H₂, marked by a sharp rise in NOₓ and a steep decline in NH₃ slip. An optimal trade-off was observed at 12 % H₂, where NH₃ slip decreased from 2626 to 1336 ppm, accompanied by only a 12 ppm increase in NO, while maintaining MILD conditions. Decreasing the furnace temperature extended MILD combustion to 20 % H₂, but compared to the 12 % H₂, it caused higher NH₃ slip and only a slight reduction in NO, highlighting a trade-off between temperature control and NH₃ decomposition. The experimental findings were analyzed from a chemical kinetic viewpoint using a chemical reactor network approach. The results showed that NO reduction at H₂≤20 % was dominated by thermal DeNO_x, while NO formation at H₂≤80 % primarily originated from fuel-bound nitrogen. These findings advance the understanding of NH₃-H₂ MILD combustion at realistic scales and provide insight into the design of low-emission ammonia-based systems.

氨（NH₃）是一种很有前途的无碳燃料，用于脱碳能源系统，但它在实际燃烧系统中的使用受到低火焰稳定性和NOₓ排放的阻碍。人们提出用氢（H₂）燃烧NH₃来提高传统燃烧系统的稳定性；然而，NOₓ排放可能持续或恶化。中度或强烈低氧稀释（MILD）燃烧通过分布的反应区和降低峰值温度提供了抑制NOₓ的途径。本研究的目的是稳定纯NH₃，并在半工业逆流炉中在MILD条件下加氢对其进行表征。实验证明了在没有活性增强剂的MILD条件下，纯NH₃的稳定性，导致NOₓ的排放可以忽略不计，但NH₃的滑移很大。通过分析从MILD到火焰的转变对排放的影响来评估加氢的影响。从MILD到升起的火焰的转变发生在~ 14% H₂的温度下，其标志是NOₓ的急剧上升和NH₃滑移的急剧下降。在12%的H₂下观察到一个最佳的权衡，其中NH₃滑脱从2626 ppm下降到1336 ppm，同时只增加12 ppm的NO，同时保持轻度条件。降低炉子温度使轻度燃烧延长到20%的H₂，但与12%的H₂相比，它导致了更高的NH₃滑脱和NO的轻微减少，突出了温度控制和NH₃分解之间的权衡。用化学反应网络的方法从化学动力学的角度对实验结果进行了分析。结果表明：H2≤20%时NO的还原以热脱氮为主，H2≤80%时NO的生成主要来源于燃料结合氮。这些发现促进了对NH₃-H₂MILD燃烧在现实尺度上的理解，并为低排放氨基系统的设计提供了见解。

{"title":"The influence of MILD-to-flame transition on stabilization, reactive structures, and emissions of NH3/H2 mixtures in a semi-industrial furnace","authors":"Ebrahim Rahmani , Natalia Cid , M․Mustafa Kamal , Axel Coussement , Alessandro Parente , Marco Lubrano Lavadera","doi":"10.1016/j.combustflame.2025.114687","DOIUrl":"10.1016/j.combustflame.2025.114687","url":null,"abstract":"<div><div>Ammonia (NH₃) is a promising carbon-free fuel for decarbonizing energy systems, but its use in practical combustion systems is hindered by low flame stability and NOₓ emissions. Burning NH₃ with hydrogen (H₂) has been proposed to improve stability in conventional combustion systems; however, NOₓ emissions may persist or worsen. Moderate or Intense Low-Oxygen Dilution (MILD) combustion offers a pathway to suppress NOₓ through distributed reaction zones and reduced peak temperatures. The aim of this study is to stabilize pure NH₃ and characterize it with the H₂ addition in a semi-industrial reverse-flow furnace under MILD conditions. The experiments demonstrated the stabilization of pure NH₃ under MILD conditions without reactive enhancers, resulting in negligible NOₓ emissions but significant NH₃ slip. The impact of H₂ addition was assessed by analyzing how the transition from MILD to flame influences emissions. A transition from MILD to a lifted flame occurred at ∼14 % H₂, marked by a sharp rise in NOₓ and a steep decline in NH₃ slip. An optimal trade-off was observed at 12 % H₂, where NH₃ slip decreased from 2626 to 1336 ppm, accompanied by only a 12 ppm increase in NO, while maintaining MILD conditions. Decreasing the furnace temperature extended MILD combustion to 20 % H₂, but compared to the 12 % H₂, it caused higher NH₃ slip and only a slight reduction in NO, highlighting a trade-off between temperature control and NH₃ decomposition. The experimental findings were analyzed from a chemical kinetic viewpoint using a chemical reactor network approach. The results showed that NO reduction at H<sub>2</sub>≤20 % was dominated by thermal DeNO<sub>x</sub>, while NO formation at H₂≤80 % primarily originated from fuel-bound nitrogen. These findings advance the understanding of NH₃-H₂ MILD combustion at realistic scales and provide insight into the design of low-emission ammonia-based systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114687"},"PeriodicalIF":6.2,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study on the explosion characteristics and mechanism of hydrogen at different concentrations inhibited by inert gases 不同浓度氢气在惰性气体抑制下的爆炸特性及机理研究

IF 6.2 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2025-12-02 DOI: 10.1016/j.combustflame.2025.114658

Xiaotong Wang , Baisheng Nie , Leilei Li , Weili Wang , Cheng Zhou

Hydrogen, as an important renewable energy source, is widely used but also has the potential safety hazard of explosion. Therefore, it is of great significance to study the explosion characteristics of hydrogen and the suppression mechanisms. This paper combines experimental research and numerical simulation based on the visual explosion pipeline experimental system to study the macro-inhibition laws and micro-inhibition mechanisms of hydrogen explosions by single and composite inert gases. The results showed that as the volume fraction of inert gas increased, macro explosion parameters such as explosion pressure, pressure rise rate, and detonation index all exhibited a decreasing trend. Furthermore, the critical volume fraction ranges for single and composite inert gases to completely suppress hydrogen explosions at different concentrations were determined, with the inhibitory effects of inert gases following the order CO₂ > CO₂ + N₂ > N₂. According to Chemkin simulations, the laminar flame speed of hydrogen combustion after the addition of inert gas is positively correlated with the adiabatic temperature and thermal diffusivity, and both decrease with increasing inert gas content, consistent with the change in explosion pressure. In addition, the addition of inert gases can reduce the concentration of H₂ and O₂, thereby lowering the collision probability of free radicals. Since CO₂ can also undergo chemical reactions (R32: CO + OH = H + CO₂), it consumes H free radicals and slows down the hydrogen explosion chain reaction, making CO₂ the most effective inhibitor.

氢气作为一种重要的可再生能源，用途广泛，但也存在爆炸的安全隐患。因此，研究氢气的爆炸特性和抑制机理具有重要意义。本文基于可视化爆炸管道实验系统，将实验研究与数值模拟相结合，研究了单一惰性气体和复合惰性气体对氢气爆炸的宏观抑制规律和微观抑制机理。结果表明：随着惰性气体体积分数的增加，爆炸压力、升压率、爆轰指数等宏观爆炸参数均呈减小趋势；此外，还确定了不同浓度下单一惰性气体和复合惰性气体完全抑制氢爆炸的临界体积分数范围，惰性气体的抑制效果依次为CO₂>； CO₂+ N₂> N₂。根据Chemkin模拟，加入惰性气体后氢气燃烧的层流火焰速度与绝热温度和热扩散系数呈正相关，且两者均随惰性气体含量的增加而减小，与爆炸压力的变化一致。此外，惰性气体的加入可以降低H2和O2的浓度，从而降低自由基的碰撞概率。由于CO2还可以发生化学反应（R32: CO + OH = H + CO2），它消耗H自由基，减缓氢爆炸连锁反应，使CO2成为最有效的抑制剂。

{"title":"Study on the explosion characteristics and mechanism of hydrogen at different concentrations inhibited by inert gases","authors":"Xiaotong Wang , Baisheng Nie , Leilei Li , Weili Wang , Cheng Zhou","doi":"10.1016/j.combustflame.2025.114658","DOIUrl":"10.1016/j.combustflame.2025.114658","url":null,"abstract":"<div><div>Hydrogen, as an important renewable energy source, is widely used but also has the potential safety hazard of explosion. Therefore, it is of great significance to study the explosion characteristics of hydrogen and the suppression mechanisms. This paper combines experimental research and numerical simulation based on the visual explosion pipeline experimental system to study the macro-inhibition laws and micro-inhibition mechanisms of hydrogen explosions by single and composite inert gases. The results showed that as the volume fraction of inert gas increased, macro explosion parameters such as explosion pressure, pressure rise rate, and detonation index all exhibited a decreasing trend. Furthermore, the critical volume fraction ranges for single and composite inert gases to completely suppress hydrogen explosions at different concentrations were determined, with the inhibitory effects of inert gases following the order CO₂ > CO₂ + N₂ > N₂. According to Chemkin simulations, the laminar flame speed of hydrogen combustion after the addition of inert gas is positively correlated with the adiabatic temperature and thermal diffusivity, and both decrease with increasing inert gas content, consistent with the change in explosion pressure. In addition, the addition of inert gases can reduce the concentration of H<sub>2</sub> and O<sub>2</sub>, thereby lowering the collision probability of free radicals. Since CO<sub>2</sub> can also undergo chemical reactions (R32: CO + OH = H + CO<sub>2</sub>), it consumes H free radicals and slows down the hydrogen explosion chain reaction, making CO<sub>2</sub> the most effective inhibitor.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"284 ","pages":"Article 114658"},"PeriodicalIF":6.2,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145691270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0