<div><div>In the present study, the impact of low-temperature chemistry (LTC) on critical ignition in expanding media is studied using a quasi-unsteady reactor model that accounts for both curvature and unsteadiness. Dimethyl ether–oxygen-diluent mixtures with equivalence ratio <span><math><mrow><mi>Φ</mi><mo>=</mo></mrow></math></span> 0.5 are considered. The LTC was progressively activated at the von Neumann state of planar Chapman–Jouguet detonation by progressively replacing nitrogen by carbon dioxide as diluent. To determine the effect of LTC on critical ignition, two strategies were applied. In the first one, LTC pathways were simply deactivated by removing the reaction CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>OCH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>+O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> = CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>OCH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> from the reaction model. In the second approach, the strength of LTC was enhanced by adding 1000 ppm of O<sub>3</sub>. The distance to maximum thermicity increases continuously with CO<sub>2</sub> content when LTC is deactivated, whereas it demonstrate a negative-temperature coefficient (NTC) like behavior when LTC is active. This behavior is significantly more pronounced when O<sub>3</sub> is added to the reactive mixture. Under volumetric expansion conditions, ignition or quenching can take place depending on the rate of expansion and the value of the curvature. Thermo-chemical analyses were performed to explain the dynamics of these events. The critical initiation energy is continuously increasing with CO<sub>2</sub> content when LTC is deactivated, whereas it essentially plateaus for CO<sub>2</sub> contents above 30% when LTC is activated. The possibility of experimentally studying LTC-affected detonation is discussed in detail. For DME-O<sub>2</sub>-CO<sub>2</sub>-N<sub>2</sub> mixtures, the chemical length-scales are very likely too large to enable an experimental observation. On the other hand, if the LTC can be significantly enhanced by a large addition of O<sub>3</sub>, the length-scale could become compatible with an experimental observation of LTC-affected detonation, albeit such experiments would be very challenging and would require a large-scale facility.</div><div><strong>Novelty and Significance Statement</strong> The potential importance of low-temperature chemistry (LTC) on detonation characteristics remains an open question. In the present study, we present the first investigation on the effect of low-temperature chemistry on direct detonation initiation using a quasi-unsteady model along with the Taylor–Sedov blast wave model. Thermo-chemical analyses were performed to explain the dynamics of igni
本文采用考虑曲率和非定常的准非定常反应器模型，研究了低温化学（LTC）对膨胀介质中临界点火的影响。考虑当量比Φ= 0.5的二甲醚-氧-稀释剂混合物。在平面Chapman-Jouguet爆炸的冯诺依曼状态下，LTC逐渐被二氧化碳作为稀释剂取代氮而被激活。为了确定LTC对临界点火的影响，采用了两种策略。在第一种方法中，通过从反应模型中去除反应CH3OCH2+O2 = CH3OCH2O2，简单地使LTC通路失活。在第二种方法中，通过添加1000ppm的O3来增强LTC的强度。当LTC失活时，与最大热度的距离随着CO2含量的增加而持续增加，而当LTC激活时，其表现出类似负温度系数（NTC）的行为。当O3加入到反应混合物中时，这种行为更加明显。在体积膨胀条件下，点火或淬火的发生取决于膨胀速率和曲率值。进行了热化学分析来解释这些事件的动力学。当LTC失活时，临界起始能随CO2含量的增加而不断增加，而当LTC激活后，当CO2含量超过30%时，临界起始能基本趋于平稳。详细讨论了实验研究ltc影响爆轰的可能性。对于二甲醚- o2 - co2 - n2混合物，化学长度尺度很可能太大，无法进行实验观察。另一方面，如果LTC可以通过大量添加O3而显着增强，则长度尺度可以与LTC影响爆炸的实验观察相兼容，尽管此类实验将非常具有挑战性并且需要大型设施。低温化学（LTC）对爆轰特性的潜在重要性仍然是一个悬而未决的问题。在本研究中，我们首次使用准非定常模型和Taylor-Sedov爆炸波模型研究低温化学对直接爆轰起爆的影响。热化学分析解释了膨胀条件下的点火和猝灭动力学。低温化学激活时，CO2含量在30%以上达到临界起爆能平台。虽然它们的长度尺度看起来非常大，但如果在混合物中加入大量的臭氧以显着提高LTC，并采用大型设施，则不能完全排除LTC影响爆轰的存在。目前的结果与工业安全以及对爆震波结构和动力学的基本认识有关。
{"title":"Critical ignition in dimethyl ether–oxygen–carbon dioxide mixtures: Effects of low-temperature chemistry and ozone addition","authors":"Zhaoyuan Huang , Rémy Mével , Xinqian Zheng , Gaofeng Wang","doi":"10.1016/j.combustflame.2025.114756","DOIUrl":"10.1016/j.combustflame.2025.114756","url":null,"abstract":"<div><div>In the present study, the impact of low-temperature chemistry (LTC) on critical ignition in expanding media is studied using a quasi-unsteady reactor model that accounts for both curvature and unsteadiness. Dimethyl ether–oxygen-diluent mixtures with equivalence ratio <span><math><mrow><mi>Φ</mi><mo>=</mo></mrow></math></span> 0.5 are considered. The LTC was progressively activated at the von Neumann state of planar Chapman–Jouguet detonation by progressively replacing nitrogen by carbon dioxide as diluent. To determine the effect of LTC on critical ignition, two strategies were applied. In the first one, LTC pathways were simply deactivated by removing the reaction CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>OCH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>+O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> = CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>OCH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> from the reaction model. In the second approach, the strength of LTC was enhanced by adding 1000 ppm of O<sub>3</sub>. The distance to maximum thermicity increases continuously with CO<sub>2</sub> content when LTC is deactivated, whereas it demonstrate a negative-temperature coefficient (NTC) like behavior when LTC is active. This behavior is significantly more pronounced when O<sub>3</sub> is added to the reactive mixture. Under volumetric expansion conditions, ignition or quenching can take place depending on the rate of expansion and the value of the curvature. Thermo-chemical analyses were performed to explain the dynamics of these events. The critical initiation energy is continuously increasing with CO<sub>2</sub> content when LTC is deactivated, whereas it essentially plateaus for CO<sub>2</sub> contents above 30% when LTC is activated. The possibility of experimentally studying LTC-affected detonation is discussed in detail. For DME-O<sub>2</sub>-CO<sub>2</sub>-N<sub>2</sub> mixtures, the chemical length-scales are very likely too large to enable an experimental observation. On the other hand, if the LTC can be significantly enhanced by a large addition of O<sub>3</sub>, the length-scale could become compatible with an experimental observation of LTC-affected detonation, albeit such experiments would be very challenging and would require a large-scale facility.</div><div><strong>Novelty and Significance Statement</strong> The potential importance of low-temperature chemistry (LTC) on detonation characteristics remains an open question. In the present study, we present the first investigation on the effect of low-temperature chemistry on direct detonation initiation using a quasi-unsteady model along with the Taylor–Sedov blast wave model. Thermo-chemical analyses were performed to explain the dynamics of igni","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114756"},"PeriodicalIF":6.2,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922299","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}
Pub Date : 2026-01-05DOI: 10.1016/j.combustflame.2025.114757
Yu Wang , Wei Yao , Jianwen Liu , Xisheng Luo
<div><div>The thermochemical nonequilibrium effect on hydrogen- and ethylene-fueled supersonic combustion was modeled in the framework of a two-temperature-based Dynamic Zone Flamelet Model (DZFM) with up to 221.21 million cells. The numerical predictions of wall pressure match well with the experimental data for both the cold and reacting cases. Thermal nonequilibrium is first introduced by the inlet compression, then intensified by the jet-excited shock wave and expansion wave, and eventually emerges again in the divergent nozzle after a temporal equilibrium status. Delayed ignition was observed under nonequilibrium for both hydrogen and ethylene combustion. The relative importance of <span><math><msub><mi>T</mi><mi>t</mi></msub></math></span> and <span><math><msub><mi>T</mi><mi>v</mi></msub></math></span> on elementary reactions under different degrees of thermal nonequilibrium (<span><math><mrow><msub><mi>T</mi><mi>v</mi></msub><mo>/</mo><msub><mi>T</mi><mi>t</mi></msub></mrow></math></span>) was analyzed using reaction path flux analysis over the typical temperature range in scramjets. Inverse reaction path directions were observed in the hydrogen ignition process between equilibrium and nonequilibrium. The reaction rate of the chain branching reaction <span><math><mrow><mrow><mi>H</mi><mspace></mspace><mo>+</mo><mspace></mspace></mrow><msub><mi>O</mi><mn>2</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace><mi>O</mi><mspace></mspace><mo>+</mo><mspace></mspace><mtext>OH</mtext></mrow></mrow></math></span> is dominated by <span><math><msub><mi>T</mi><mi>v</mi></msub></math></span> under intense thermal nonequilibrium (<span><math><mrow><msub><mi>T</mi><mi>v</mi></msub><mo>/</mo><msub><mi>T</mi><mi>t</mi></msub><mrow><mo><</mo><mn>0</mn></mrow><mrow><mo>.</mo><mn>5</mn></mrow></mrow></math></span>). Inhibition of <span><math><mrow><mrow><mi>H</mi><mspace></mspace><mo>+</mo><mspace></mspace></mrow><msub><mi>O</mi><mn>2</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace><mi>O</mi><mspace></mspace><mo>+</mo><mspace></mspace><mtext>OH</mtext></mrow></mrow></math></span> results in delayed hydrogen ignition under nonequilibrium. For the ethylene case, the inhibition of the dissociation reactions <span><math><mrow><msub><mi>C</mi><mn>2</mn></msub><msub><mi>H</mi><mn>4</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace></mrow><msub><mi>C</mi><mn>2</mn></msub><msub><mi>H</mi><mrow><mn>3</mn><mspace></mspace></mrow></msub><mrow><mo>+</mo><mspace></mspace><mi>H</mi></mrow></mrow></math></span> and <span><math><mrow><msub><mi>C</mi><mn>2</mn></msub><msub><mi>H</mi><mn>3</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace></mrow><msub><mi>C</mi><mn>2</mn></msub><mrow><mi>H</mi><mspace></mspace><mo>+</mo><mspace></mspace></mrow><msub><mi>H</mi><mn>2</mn></msub></mrow></math></span> dramatically decreases the concentration of active radicals, leading to delayed ignition under nonequilibrium. The thermochemical noneq
{"title":"Thermochemical nonequilibrium effect on hydrogen- and ethylene-fueled supersonic combustion","authors":"Yu Wang , Wei Yao , Jianwen Liu , Xisheng Luo","doi":"10.1016/j.combustflame.2025.114757","DOIUrl":"10.1016/j.combustflame.2025.114757","url":null,"abstract":"<div><div>The thermochemical nonequilibrium effect on hydrogen- and ethylene-fueled supersonic combustion was modeled in the framework of a two-temperature-based Dynamic Zone Flamelet Model (DZFM) with up to 221.21 million cells. The numerical predictions of wall pressure match well with the experimental data for both the cold and reacting cases. Thermal nonequilibrium is first introduced by the inlet compression, then intensified by the jet-excited shock wave and expansion wave, and eventually emerges again in the divergent nozzle after a temporal equilibrium status. Delayed ignition was observed under nonequilibrium for both hydrogen and ethylene combustion. The relative importance of <span><math><msub><mi>T</mi><mi>t</mi></msub></math></span> and <span><math><msub><mi>T</mi><mi>v</mi></msub></math></span> on elementary reactions under different degrees of thermal nonequilibrium (<span><math><mrow><msub><mi>T</mi><mi>v</mi></msub><mo>/</mo><msub><mi>T</mi><mi>t</mi></msub></mrow></math></span>) was analyzed using reaction path flux analysis over the typical temperature range in scramjets. Inverse reaction path directions were observed in the hydrogen ignition process between equilibrium and nonequilibrium. The reaction rate of the chain branching reaction <span><math><mrow><mrow><mi>H</mi><mspace></mspace><mo>+</mo><mspace></mspace></mrow><msub><mi>O</mi><mn>2</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace><mi>O</mi><mspace></mspace><mo>+</mo><mspace></mspace><mtext>OH</mtext></mrow></mrow></math></span> is dominated by <span><math><msub><mi>T</mi><mi>v</mi></msub></math></span> under intense thermal nonequilibrium (<span><math><mrow><msub><mi>T</mi><mi>v</mi></msub><mo>/</mo><msub><mi>T</mi><mi>t</mi></msub><mrow><mo><</mo><mn>0</mn></mrow><mrow><mo>.</mo><mn>5</mn></mrow></mrow></math></span>). Inhibition of <span><math><mrow><mrow><mi>H</mi><mspace></mspace><mo>+</mo><mspace></mspace></mrow><msub><mi>O</mi><mn>2</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace><mi>O</mi><mspace></mspace><mo>+</mo><mspace></mspace><mtext>OH</mtext></mrow></mrow></math></span> results in delayed hydrogen ignition under nonequilibrium. For the ethylene case, the inhibition of the dissociation reactions <span><math><mrow><msub><mi>C</mi><mn>2</mn></msub><msub><mi>H</mi><mn>4</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace></mrow><msub><mi>C</mi><mn>2</mn></msub><msub><mi>H</mi><mrow><mn>3</mn><mspace></mspace></mrow></msub><mrow><mo>+</mo><mspace></mspace><mi>H</mi></mrow></mrow></math></span> and <span><math><mrow><msub><mi>C</mi><mn>2</mn></msub><msub><mi>H</mi><mn>3</mn></msub><mrow><mspace></mspace><mo>=</mo><mspace></mspace></mrow><msub><mi>C</mi><mn>2</mn></msub><mrow><mi>H</mi><mspace></mspace><mo>+</mo><mspace></mspace></mrow><msub><mi>H</mi><mn>2</mn></msub></mrow></math></span> dramatically decreases the concentration of active radicals, leading to delayed ignition under nonequilibrium. The thermochemical noneq","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114757"},"PeriodicalIF":6.2,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922386","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}
Pub Date : 2026-01-03DOI: 10.1016/j.combustflame.2025.114762
Huiquan Duan , Huajie Wang , Chongchong Ren , Min Liu , Shuzhan Bai , Guoxiang Li , Ming Jia
The elucidation of the influencing mechanism of ambient hydrogen (H2) doping on high-pressure fuel spray combustion is crucial for the realization of precise combustion control of H2 pilot-ignition engines. Attributed to the superior properties as a fuel alternative, the spray combustion characteristics of polyoxymethylene dimethyl ether 3 (PODE3) were comprehensively investigated under wide H2 doping and fuel supply conditions in this study. The results indicated that the chemical effect of ambient H2 doping dominates the PODE3 spray combustion, and the physical effect is negligible. With the H2 adoption, the competitive relationship between OH+H2=H + H2O and PODE3+OH=PODE3RX1+H2O determines the ignition delay of the PODE3/H2 mixtures. With the increase in H2 addition, the sensitivity coefficient of OH+H2=H + H2O rapidly increases, lengthening the ignition delay of PODE3 spray combustion. Under non-H2 doping conditions, the OH is mainly distributed on the sides, but the C2H2 produced by the oxidation of the high-concentration fuel/air mixture is mainly located at the center, which is oxidized as it arrives at the flame region. The difference in the distribution of the OH and C2H2 limits the C2H2 oxidation. With the H2 addition, the combustion of the fuel with the entrained H2 results in a large amount of OH at the upper region where the C2H2 is primarily produced, which can promote the C2H2 oxidation. For both non-H2 and H2 doping conditions, the ignition delay of the second injection firstly reduces and then remains unchanged with the increased injection interval under the double-injection strategies. This mainly results from the combined effects of the reduction of the H2 concentration at the PODE3 spray path and the decreased local temperature.
{"title":"Investigation on the influence of ambient hydrogen doping on the spray combustion characteristics of polyoxymethylene dimethyl ether 3 (PODE3) towards combustion control of hydrogen pilot-ignition engines","authors":"Huiquan Duan , Huajie Wang , Chongchong Ren , Min Liu , Shuzhan Bai , Guoxiang Li , Ming Jia","doi":"10.1016/j.combustflame.2025.114762","DOIUrl":"10.1016/j.combustflame.2025.114762","url":null,"abstract":"<div><div>The elucidation of the influencing mechanism of ambient hydrogen (H2) doping on high-pressure fuel spray combustion is crucial for the realization of precise combustion control of H2 pilot-ignition engines. Attributed to the superior properties as a fuel alternative, the spray combustion characteristics of polyoxymethylene dimethyl ether 3 (PODE3) were comprehensively investigated under wide H2 doping and fuel supply conditions in this study. The results indicated that the chemical effect of ambient H2 doping dominates the PODE3 spray combustion, and the physical effect is negligible. With the H2 adoption, the competitive relationship between OH+H2=<em>H</em> + H2O and PODE3+OH=PODE3RX1+H2O determines the ignition delay of the PODE3/H2 mixtures. With the increase in H2 addition, the sensitivity coefficient of OH+H2=<em>H</em> + H2O rapidly increases, lengthening the ignition delay of PODE3 spray combustion. Under non-H2 doping conditions, the OH is mainly distributed on the sides, but the C2H2 produced by the oxidation of the high-concentration fuel/air mixture is mainly located at the center, which is oxidized as it arrives at the flame region. The difference in the distribution of the OH and C2H2 limits the C2H2 oxidation. With the H2 addition, the combustion of the fuel with the entrained H2 results in a large amount of OH at the upper region where the C2H2 is primarily produced, which can promote the C2H2 oxidation. For both non-H2 and H2 doping conditions, the ignition delay of the second injection firstly reduces and then remains unchanged with the increased injection interval under the double-injection strategies. This mainly results from the combined effects of the reduction of the H2 concentration at the PODE3 spray path and the decreased local temperature.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114762"},"PeriodicalIF":6.2,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881445","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}
In this work, the single iron particle combustion platform was modified to be a wall impact test platform, traced the impact behaviors of burning iron particles with a high speed camera and a long focal macro lens. Three fundamental impact modes were identified: liquid-phase adhesion, liquid-phase rebound, and solid-phase rebound. The significant reduction of self-luminous intensity was observed for two liquid-phase modes, which indicated wall heat transfer played a dominant role in the impact process of liquid-phase particles. Furthermore, micro-explosion of burning iron particles were observed during the whole impact process and behaved in three modes: cooling-induced, impact-induced, and cavity formation. This probably caused by the high pressure gases generated by chemical reactions of impurities by discussing three generation mechanisms proposed previously. To understand the impact behavior quantitatively, kinetic analysis of burning iron particle impact was carried out and a model was developed for predicting the maximum dimensionless spreading factor of burning iron droplets. The model performance was improved when adhering and rebounding droplets were considered separately. Finally, a statistical analysis revealed that larger particles have higher adhesion probabilities at the lower height. As the height increased, the adhesion probabilities of all particles decreased significantly, which were more pronounced for larger particles. The empirical model derived in this study can be incorporated into future models for iron particle impact, which is expected to aid the recognition of iron combustion.
Novelty and significance statement
A comprehensive investigation on the impact behavior of burning iron particles was carried out for the first time to the best of authors’ knowledge. A serious of interesting phenomenon were identified during impact, including liquid-phase adhesion, liquid-phase rebound, solid-phase rebound and micro-explosion. Specifically, micro-explosion was found to behave in the modes of cooling-induced, impact-induced, and cavity formation. Essential kinetic mechanism was elucidated for iron droplet impact with predictive models proposed for droplet spreading and adhesion probability. These findings offered critical insights for improving wall surface slagging of iron-fired boiler.
{"title":"Wall impact dynamics of a single burning micron-sized iron particle","authors":"Yilan Yang, Longkai Zhang, Haiyang Zhang, Qianqian Li, Xiao Cai, Hu Liu, Jinhua Wang, Zuohua Huang","doi":"10.1016/j.combustflame.2025.114735","DOIUrl":"10.1016/j.combustflame.2025.114735","url":null,"abstract":"<div><div>In this work, the single iron particle combustion platform was modified to be a wall impact test platform, traced the impact behaviors of burning iron particles with a high speed camera and a long focal macro lens. Three fundamental impact modes were identified: liquid-phase adhesion, liquid-phase rebound, and solid-phase rebound. The significant reduction of self-luminous intensity was observed for two liquid-phase modes, which indicated wall heat transfer played a dominant role in the impact process of liquid-phase particles. Furthermore, micro-explosion of burning iron particles were observed during the whole impact process and behaved in three modes: cooling-induced, impact-induced, and cavity formation. This probably caused by the high pressure gases generated by chemical reactions of impurities by discussing three generation mechanisms proposed previously. To understand the impact behavior quantitatively, kinetic analysis of burning iron particle impact was carried out and a model was developed for predicting the maximum dimensionless spreading factor of burning iron droplets. The model performance was improved when adhering and rebounding droplets were considered separately. Finally, a statistical analysis revealed that larger particles have higher adhesion probabilities at the lower height. As the height increased, the adhesion probabilities of all particles decreased significantly, which were more pronounced for larger particles. The empirical model derived in this study can be incorporated into future models for iron particle impact, which is expected to aid the recognition of iron combustion.</div></div><div><h3>Novelty and significance statement</h3><div>A comprehensive investigation on the impact behavior of burning iron particles was carried out for the first time to the best of authors’ knowledge. A serious of interesting phenomenon were identified during impact, including liquid-phase adhesion, liquid-phase rebound, solid-phase rebound and micro-explosion. Specifically, micro-explosion was found to behave in the modes of cooling-induced, impact-induced, and cavity formation. Essential kinetic mechanism was elucidated for iron droplet impact with predictive models proposed for droplet spreading and adhesion probability. These findings offered critical insights for improving wall surface slagging of iron-fired boiler.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114735"},"PeriodicalIF":6.2,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881334","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}
Pub Date : 2026-01-03DOI: 10.1016/j.combustflame.2025.114759
Andre Molina, Miguel J. Camarena, Evgeny Shafirovich
The difficult ignition and low combustion efficiency of boron particles decrease the performance of boron-loaded, fuel-rich propellants for solid fuel ramjets and ducted rockets. One approach to solving this problem involves the use of magnesium diboride (MgB2), which ignites easier than boron. Magnesium tetraboride (MgB4) offers greater energy density owing to its higher boron content. However, the effect of B/Mg ratio on the ignition and combustion is unknown. Additionally, while nanoscale MgB₂ particles and quasi-2D structures are promising energetic additives, the oxidation and combustion properties of nanoscale MgB₄ have not been explored. To address these knowledge gaps, the present work included synthesis and high-energy ball milling of MgB2 and MgB4 powders, thermogravimetric analysis (TGA) of their oxidation, and combustion experiments with thin layers of the obtained powders. Comparison of two synthesis routes (a solid-state reaction in a tube furnace and combustion synthesis) has shown that the former is the superior method for producing magnesium borides. TGA has revealed that oxidation of both MgB2 and MgB4 results in a high conversion into the oxides (88–91 %), far exceeding the low conversion of boron (62.5 %). MgB4 begins to oxidize rapidly at a much lower temperature (∼900 °C) than MgB2 (∼1200 °C). The burning rates of milled MgB2 and MgB4 are about eight and five times, respectively, faster than that of submicron boron. Magnesium borides exhibit a stable, sustained boron flame, needed for high combustion efficiency, whereas physical Mg/B mixtures undergo Mg-driven "flash" combustion.
{"title":"Fabrication, oxidation, and combustion of nanoscale magnesium diboride and tetraboride","authors":"Andre Molina, Miguel J. Camarena, Evgeny Shafirovich","doi":"10.1016/j.combustflame.2025.114759","DOIUrl":"10.1016/j.combustflame.2025.114759","url":null,"abstract":"<div><div>The difficult ignition and low combustion efficiency of boron particles decrease the performance of boron-loaded, fuel-rich propellants for solid fuel ramjets and ducted rockets. One approach to solving this problem involves the use of magnesium diboride (MgB<sub>2</sub>), which ignites easier than boron. Magnesium tetraboride (MgB<sub>4</sub>) offers greater energy density owing to its higher boron content. However, the effect of B/Mg ratio on the ignition and combustion is unknown. Additionally, while nanoscale MgB₂ particles and quasi-2D structures are promising energetic additives, the oxidation and combustion properties of nanoscale MgB₄ have not been explored. To address these knowledge gaps, the present work included synthesis and high-energy ball milling of MgB<sub>2</sub> and MgB<sub>4</sub> powders, thermogravimetric analysis (TGA) of their oxidation, and combustion experiments with thin layers of the obtained powders. Comparison of two synthesis routes (a solid-state reaction in a tube furnace and combustion synthesis) has shown that the former is the superior method for producing magnesium borides. TGA has revealed that oxidation of both MgB<sub>2</sub> and MgB<sub>4</sub> results in a high conversion into the oxides (88–91 %), far exceeding the low conversion of boron (62.5 %). MgB<sub>4</sub> begins to oxidize rapidly at a much lower temperature (∼900 °C) than MgB<sub>2</sub> (∼1200 °C). The burning rates of milled MgB<sub>2</sub> and MgB<sub>4</sub> are about eight and five times, respectively, faster than that of submicron boron. Magnesium borides exhibit a stable, sustained boron flame, needed for high combustion efficiency, whereas physical Mg/B mixtures undergo Mg-driven \"flash\" combustion.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114759"},"PeriodicalIF":6.2,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922385","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}
Pub Date : 2026-01-03DOI: 10.1016/j.combustflame.2025.114763
Mayank Pandey, Krishnakant Agrawal, Anjan Ray
<div><div>Pulsating and cellular flame instabilities have been predicted to develop at different Lewis number ranges due to the variation of disparity between heat and mass diffusion. In this work, pulsating flame instability is demonstrated in freely propagating rich H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air premixed flames for the first time using two-dimensional simulations with detailed chemistry. The high Ze(Le-1) values required for pulsating instability can be achieved by increasing the operating pressure for such mixtures. The flames were found to be stable at 8 atm and developed into a longitudinal pulsating flame for 12 atm. As pressure increases, the flames with initial longitudinal pulsation transition to transverse waves at pressures of 16 and 20 atm. Before this observation, to systematically understand the independent effects of the Lewis number on cellular instability, the composition of the H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>-O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>-N<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> mixture is varied while keeping the density ratio and unstretched laminar flame speed constant. Numerical linear stability analyses show that a decrease in Lewis number increases the maximum growth rate, indicating enhanced cellular instability. Flames with low adiabatic temperatures, i.e., a low density ratio and Peclet numbers, are prone to high growth rates. As adiabatic temperatures increase and the flame strengthens, the growth rate decreases. The maximum growth rate increases with the instability parameter <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> and the ratio of Zeldovich and Peclet numbers (Ze/Pe), both of which are related to thermodiffusive effects. For the non-linear flame propagation, the overall flame propagation speed increases with a reduction in Lewis number and adiabatic flame temperature. The present study parametrically explores ranges of relevant non-dimensional numbers using real mixture compositions and demonstrates the dominance of different modes of intrinsic flame instabilities with physical details.</div><div><strong>Novelty and Significance Statement</strong></div><div>The novelty of this paper lies in demonstrating transverse waves in rich hydrogen/air flames by exploring a large Ze(Le-1) number in a two-dimensional computational model with detailed chemistry and transport for the first time. This paper contributes to understanding pulsating instabilities and their morphological characteristics for a realistic mixture. The Lewis number is systematically varied at a constant density ratio and approximately the same unstretched laminar flame speed by varying the molar ratio of N<sub>2</sub> to O<sub>2</sub> in atmospheric air. This enables the quantification of the independent impact of this critical non-dime
{"title":"Numerical studies on cellular and pulsating instabilities in hydrogen flames","authors":"Mayank Pandey, Krishnakant Agrawal, Anjan Ray","doi":"10.1016/j.combustflame.2025.114763","DOIUrl":"10.1016/j.combustflame.2025.114763","url":null,"abstract":"<div><div>Pulsating and cellular flame instabilities have been predicted to develop at different Lewis number ranges due to the variation of disparity between heat and mass diffusion. In this work, pulsating flame instability is demonstrated in freely propagating rich H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air premixed flames for the first time using two-dimensional simulations with detailed chemistry. The high Ze(Le-1) values required for pulsating instability can be achieved by increasing the operating pressure for such mixtures. The flames were found to be stable at 8 atm and developed into a longitudinal pulsating flame for 12 atm. As pressure increases, the flames with initial longitudinal pulsation transition to transverse waves at pressures of 16 and 20 atm. Before this observation, to systematically understand the independent effects of the Lewis number on cellular instability, the composition of the H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>-O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>-N<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> mixture is varied while keeping the density ratio and unstretched laminar flame speed constant. Numerical linear stability analyses show that a decrease in Lewis number increases the maximum growth rate, indicating enhanced cellular instability. Flames with low adiabatic temperatures, i.e., a low density ratio and Peclet numbers, are prone to high growth rates. As adiabatic temperatures increase and the flame strengthens, the growth rate decreases. The maximum growth rate increases with the instability parameter <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> and the ratio of Zeldovich and Peclet numbers (Ze/Pe), both of which are related to thermodiffusive effects. For the non-linear flame propagation, the overall flame propagation speed increases with a reduction in Lewis number and adiabatic flame temperature. The present study parametrically explores ranges of relevant non-dimensional numbers using real mixture compositions and demonstrates the dominance of different modes of intrinsic flame instabilities with physical details.</div><div><strong>Novelty and Significance Statement</strong></div><div>The novelty of this paper lies in demonstrating transverse waves in rich hydrogen/air flames by exploring a large Ze(Le-1) number in a two-dimensional computational model with detailed chemistry and transport for the first time. This paper contributes to understanding pulsating instabilities and their morphological characteristics for a realistic mixture. The Lewis number is systematically varied at a constant density ratio and approximately the same unstretched laminar flame speed by varying the molar ratio of N<sub>2</sub> to O<sub>2</sub> in atmospheric air. This enables the quantification of the independent impact of this critical non-dime","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114763"},"PeriodicalIF":6.2,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881443","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}
Pub Date : 2026-01-02DOI: 10.1016/j.combustflame.2025.114723
Zifeng Weng , Fernando Veiga-Lopez , Rémy Mével , Gaofeng Wang
As ammonia appears as one of the most promising renewable energy carriers of the future, it is of critical importance to fill the gaps in the understanding of its combustion properties in the perspective of developing real industrial applications. With the objective to contribute to the complete understanding of ammonia combustion properties, this works analyzes the effect on laminar flame speed of modeling ammonia-oxygen and ammonia-enriched air as a mixtures of real gas. Results show quantitative and qualitative discrepancies with ideal gas modeling when increasing the mixtures temperature and pressure along the saturation curve of ammonia. Results indicate that, for near-ambient temperature, real gas effects should be included in the uncertainty calculation for pressure as low as approximately 350 kPa for ammonia-oxygen mixtures and 700 kPa for ammonia-oxygen enriched air mixtures. Given high pressure and temperature conditions, discrepancies up to 29% in the laminar flame speed are obtained. Moreover, the laminar flame speed demonstrates different qualitative evolution when changing the gas models; it decreases/increases when and K for real gas/ideal gas models. The main driver is the inclusion of the real gas equation of state and thermodynamics, while high-pressure transport models and kinetics are less important. Real gas effects should therefore be included in future analyses for the correct assessment of ammonia combustion properties, mostly for high-pressure industrial applications.
Novelty and significance statement
The novelty of this research is to include real gas (RG) modeling to compute ammonia-based mixtures laminar flame speed (LFS). It is significant because (i) ammonia is a promising energy carrier of renewable energy, and (ii) modeling ammonia-based mixtures as a RG induces major changes in LFS predictions along the saturation curve of ammonia. Given high pressure and temperature, RG mixtures yield a LFS up to 29% lower than obtained when considering the ideal gas model. Moreover, the qualitative trends of LFS along the saturation curve diverge between the two models. The main RG effects are shown to be related to the modification of the equation of state and associated thermodynamics. We conclude that RG modeling should be in general included for simulating the combustion of ammonia-based mixtures, which is an outcome of primary importance for the community.
{"title":"Laminar flame speed of ammonia-oxygen and ammonia-oxygen enriched air mixtures near saturation conditions","authors":"Zifeng Weng , Fernando Veiga-Lopez , Rémy Mével , Gaofeng Wang","doi":"10.1016/j.combustflame.2025.114723","DOIUrl":"10.1016/j.combustflame.2025.114723","url":null,"abstract":"<div><div>As ammonia appears as one of the most promising renewable energy carriers of the future, it is of critical importance to fill the gaps in the understanding of its combustion properties in the perspective of developing real industrial applications. With the objective to contribute to the complete understanding of ammonia combustion properties, this works analyzes the effect on laminar flame speed of modeling ammonia-oxygen and ammonia-enriched air as a mixtures of real gas. Results show quantitative and qualitative discrepancies with ideal gas modeling when increasing the mixtures temperature and pressure along the saturation curve of ammonia. Results indicate that, for near-ambient temperature, real gas effects should be included in the uncertainty calculation for pressure as low as approximately 350 kPa for ammonia-oxygen mixtures and 700 kPa for ammonia-oxygen enriched air mixtures. Given high pressure and temperature conditions, discrepancies up to 29% in the laminar flame speed are obtained. Moreover, the laminar flame speed demonstrates different qualitative evolution when changing the gas models; it decreases/increases when <span><math><mrow><mi>P</mi><mo>></mo><mn>1</mn><mo>.</mo><mn>062</mn><mspace></mspace><mi>MPa</mi></mrow></math></span> and <span><math><mrow><mi>T</mi><mo>></mo><mn>275</mn></mrow></math></span> K for real gas/ideal gas models. The main driver is the inclusion of the real gas equation of state and thermodynamics, while high-pressure transport models and kinetics are less important. Real gas effects should therefore be included in future analyses for the correct assessment of ammonia combustion properties, mostly for high-pressure industrial applications.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of this research is to include real gas (RG) modeling to compute ammonia-based mixtures laminar flame speed (LFS). It is significant because (i) ammonia is a promising energy carrier of renewable energy, and (ii) modeling ammonia-based mixtures as a RG induces major changes in LFS predictions along the saturation curve of ammonia. Given high pressure and temperature, RG mixtures yield a LFS up to 29% lower than obtained when considering the ideal gas model. Moreover, the qualitative trends of LFS along the saturation curve diverge between the two models. The main RG effects are shown to be related to the modification of the equation of state and associated thermodynamics. We conclude that RG modeling should be in general included for simulating the combustion of ammonia-based mixtures, which is an outcome of primary importance for the community.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114723"},"PeriodicalIF":6.2,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881338","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}
Plasma-Assisted Combustion (PAC), using Nanosecond Repetitively Pulsed (NRP) discharges, is a promising technique to stabilize lean premixed flames, which are prone to instabilities and extinction. PAC has been successfully demonstrated in various academic and semi-industrial configurations. It has been proven to be effective in preventing instabilities, improving combustion efficiency, and extending the lean blowout (LBO) limit. To transfer PAC technology toward higher Technology Readiness Levels (TRLs), numerical simulations are required by engineers for combustor design and optimization. Among the strategies available, several multi-D Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of plasma-assisted turbulent combustion have been conducted in the literature by combining phenomenological NRP discharge models with detailed or semi-detailed combustion mechanisms. While these simulations achieve good accuracy, their computational cost remains high because of the large variety of spatial and temporal scales involved in plasma, combustion, and turbulence interactions. The present work aims to develop a low-order model of flame stabilization by NRP discharges, as alternative to full 3-D CFD simulations, for the design and optimization of PAC systems at a low-CPU cost. PAC is modeled by a series of three connected canonical flame elements. First, the volume of gas affected by the plasma discharges is modeled by a Perfectly-Stirred Reactor (PSR), which employs Castela’s phenomenological NRP discharge model. Next, a Plug Flow Reactor (PFR) is employed to track the combustion reactions within the recirculation zone. Finally, a 1-D strain-imposed Premixed Counterflow Flame (PMX-CF) models the impact of these gas fluxes on the flame structure. The reduced-order model is validated against 3-D LES of the Mini-PAC configuration, and a parametric study is performed on some key modeling parameters, namely the dilution and the strain rate.
Novelty and significance statement
This work presents a novel reduced-order modeling framework for flame stabilization by Nanosecond Repetitively Pulsed plasma discharges, as an alternative to 3-D CFD simulations. The model combines classical canonical flame elements with a phenomenological representation of nanosecond plasma discharge physics, providing a unique way to capture key flame stabilization mechanisms without relying on fully resolved, computationally expensive simulations. The developed model supports both fundamental research and engineering applications, enabling broader use of plasma-assisted combustion in future clean and efficient energy and propulsion systems.
{"title":"Modeling turbulent flame enhancement by Nanosecond Repetitively Pulsed discharges using a low-order model","authors":"Stéphane Q.E. Wang, Nasser Darabiha, Benoît Fiorina","doi":"10.1016/j.combustflame.2025.114761","DOIUrl":"10.1016/j.combustflame.2025.114761","url":null,"abstract":"<div><div>Plasma-Assisted Combustion (PAC), using Nanosecond Repetitively Pulsed (NRP) discharges, is a promising technique to stabilize lean premixed flames, which are prone to instabilities and extinction. PAC has been successfully demonstrated in various academic and semi-industrial configurations. It has been proven to be effective in preventing instabilities, improving combustion efficiency, and extending the lean blowout (LBO) limit. To transfer PAC technology toward higher Technology Readiness Levels (TRLs), numerical simulations are required by engineers for combustor design and optimization. Among the strategies available, several multi-D Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of plasma-assisted turbulent combustion have been conducted in the literature by combining phenomenological NRP discharge models with detailed or semi-detailed combustion mechanisms. While these simulations achieve good accuracy, their computational cost remains high because of the large variety of spatial and temporal scales involved in plasma, combustion, and turbulence interactions. The present work aims to develop a low-order model of flame stabilization by NRP discharges, as alternative to full 3-D CFD simulations, for the design and optimization of PAC systems at a low-CPU cost. PAC is modeled by a series of three connected canonical flame elements. First, the volume of gas affected by the plasma discharges is modeled by a Perfectly-Stirred Reactor (PSR), which employs Castela’s phenomenological NRP discharge model. Next, a Plug Flow Reactor (PFR) is employed to track the combustion reactions within the recirculation zone. Finally, a 1-D strain-imposed Premixed Counterflow Flame (PMX-CF) models the impact of these gas fluxes on the flame structure. The reduced-order model is validated against 3-D LES of the Mini-PAC configuration, and a parametric study is performed on some key modeling parameters, namely the dilution and the strain rate.</div><div><strong>Novelty and significance statement</strong></div><div>This work presents a novel reduced-order modeling framework for flame stabilization by Nanosecond Repetitively Pulsed plasma discharges, as an alternative to 3-D CFD simulations. The model combines classical canonical flame elements with a phenomenological representation of nanosecond plasma discharge physics, providing a unique way to capture key flame stabilization mechanisms without relying on fully resolved, computationally expensive simulations. The developed model supports both fundamental research and engineering applications, enabling broader use of plasma-assisted combustion in future clean and efficient energy and propulsion systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114761"},"PeriodicalIF":6.2,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881444","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}
Pub Date : 2026-01-02DOI: 10.1016/j.combustflame.2025.114729
Samina Sarwar, Mirko Schoenitz, Kerri-lee A. Chintersingh
In an effort to enhance ignition and combustion of boron as a solid fuel ingredient, elemental boron was mechanically milled with 5 wt % of a metal additive (Ni, Co, Fe, Cu, Bi, Zr, or Hf). Oxidation at low heating rates, under thermal analysis conditions, showed a lower oxidation onset temperature for all milled materials, particularly for B-Bi and B-Co, at the expense of a lower overall degree of oxidation at higher temperatures. Kinetic modeling of the oxidation onset, at the stage where no significant amount of oxide had accumulated at the boron surface, was used to calculate particle burn times at combustion temperatures. Comparison with published burn times allowed prediction of combustion temperatures. For pure boron and B-Fe, the predicted combustion temperatures matched expected values, although for all other materials the predictions were too low. This work also evaluates the ignition and combustion behavior of selected boron-transition metal additive composites when used in a pyrotechnic mixture with potassium nitrate, KNO3 in air. When mixed with KNO3 as an oxidizer, and ignited by a CO2 laser, all milled powders showed a shorter ignition delay compared with pure boron. Combustion temperatures of the milled powders were just below the boron melting point compared with elemental boron, which was found to burn above the boron melting point. Similarly, significant B-O gas phase products were observed spectroscopically for pure boron, but not for the milled composites. Captured combustion products were consistent with gas phase condensation for pure boron, while larger molten droplets and crystalline formations dominated for the milled composites. The combined results demonstrate that the studied metal additives cause boron to combust in the condensed phase, with temperatures and burn times that can be tailored by the choice of additives.
{"title":"Oxidation kinetics and pyrotechnic cloud combustion of transition metal- enhanced boron particles","authors":"Samina Sarwar, Mirko Schoenitz, Kerri-lee A. Chintersingh","doi":"10.1016/j.combustflame.2025.114729","DOIUrl":"10.1016/j.combustflame.2025.114729","url":null,"abstract":"<div><div>In an effort to enhance ignition and combustion of boron as a solid fuel ingredient, elemental boron was mechanically milled with 5 wt % of a metal additive (Ni, Co, Fe, Cu, Bi, Zr, or Hf). Oxidation at low heating rates, under thermal analysis conditions, showed a lower oxidation onset temperature for all milled materials, particularly for B-Bi and B-Co, at the expense of a lower overall degree of oxidation at higher temperatures. Kinetic modeling of the oxidation onset, at the stage where no significant amount of oxide had accumulated at the boron surface, was used to calculate particle burn times at combustion temperatures. Comparison with published burn times allowed prediction of combustion temperatures. For pure boron and B-Fe, the predicted combustion temperatures matched expected values, although for all other materials the predictions were too low. This work also evaluates the ignition and combustion behavior of selected boron-transition metal additive composites when used in a pyrotechnic mixture with potassium nitrate, KNO<sub>3</sub> in air. When mixed with KNO<sub>3</sub> as an oxidizer, and ignited by a CO<sub>2</sub> laser, all milled powders showed a shorter ignition delay compared with pure boron. Combustion temperatures of the milled powders were just below the boron melting point compared with elemental boron, which was found to burn above the boron melting point. Similarly, significant B-O gas phase products were observed spectroscopically for pure boron, but not for the milled composites. Captured combustion products were consistent with gas phase condensation for pure boron, while larger molten droplets and crystalline formations dominated for the milled composites. The combined results demonstrate that the studied metal additives cause boron to combust in the condensed phase, with temperatures and burn times that can be tailored by the choice of additives.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114729"},"PeriodicalIF":6.2,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881339","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}
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