Combustion and Flame最新文献_第3页

An experimental, theoretical and kinetic modeling study of the N2O-H2 system: Implications for N2O + H N2O-H2 系统的实验、理论和动力学模型研究：对 N2O + H

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-11-04 DOI: 10.1016/j.combustflame.2024.113810

Peter Glarborg , Eva Fabricius-Bjerre , Tor K. Joensen , Hamid Hashemi , Stephen J. Klippenstein

The reaction of N

_{2}

O with H is the key step in consumption of nitrous oxide in thermal processes. The major product channel is N

_{2}

+ OH, while NH + NO constitute minor products. In addition, a pathway involving HNNO, initiated by N

_{2}

O + H (+M)

⇄

HNNO (+M) (R3, R4), has been inferred from experiment and theory by Burke and coworkers. At longer reaction times, the reaction may reach partial equilibration, and in addition to k

_{3}

and k

_{4}

the importance of this channel depends on the thermodynamic properties of HNNO and its consumption reactions, mainly HNNO + H. In the present work, we re-examined the thermochemistry of HNNO and calculated rate constants and branching fractions for the HNNO + H reaction. Experiments on the N

_{2}

O–H

_{2}

system were conducted in a high-pressure flow reactor at 100 atm as a function of temperature (600-925 K) and stoichiometry and explained in terms of an updated chemical kinetic model. The results support the importance of the HNNO pathway, which results in inhibition of N

_{2}

O consumption and formation of NH

_{3}

. In addition, selected literature results on the N

_{2}

O–H

_{2}

system are re-examined and the implications for the other product channels of N

_{2}

O + H, in particular NH + NO, are discussed.

Novelty and significance statement

This study provides the first detailed kinetic analysis of the N

_{2}

O/H

_{2}

system at high pressure and intermediate temperatures, based on flow reactor results and high-level theoretical calculations. The experimental conditions augment the importance of a reaction pathway involving HNNO as intermediate. Inclusion in the model of a subset for HNNO, including present calculations for HNNO + H, is crucial for capturing the observed behavior.

一氧化二氮与 H 的反应是热过程中消耗一氧化二氮的关键步骤。主要产物途径是 N2 + OH，次要产物是 NH + NO。此外，Burke 和同事们还通过实验和理论推断出一条涉及 HNNO 的途径，即由 N2O + H (+M) ⇄ HNNO (+M) (R3, R4) 引发。在较长的反应时间内，反应可能会达到部分平衡，除 k3 和 k4 外，这一通道的重要性还取决于 HNNO 及其消耗反应（主要是 HNNO + H）的热力学性质。在本研究中，我们重新研究了 HNNO 的热化学性质，并计算了 HNNO + H 反应的速率常数和支化分数。在 100 atm 的高压流动反应器中进行了 N2O-H2 系统的实验，实验结果是温度（600-925 K）和化学计量的函数，并用最新的化学动力学模型进行了解释。结果证明了 HNNO 途径的重要性，该途径可抑制 N2O 的消耗和 NH3 的形成。此外，还重新审查了有关 N2O-H2 系统的部分文献结果，并讨论了 N2O + H 的其他产物途径（尤其是 NH + NO）的影响。新颖性和重要性声明本研究基于流动反应器结果和高级理论计算，首次对高压和中温条件下的 N2O/H2 系统进行了详细的动力学分析。实验条件增强了以 HNNO 为中间体的反应途径的重要性。在模型中加入 HNNO 子集，包括目前对 HNNO + H 的计算，对于捕捉观察到的行为至关重要。

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引用次数: 0

Numerical simulation of flame propagation characteristics of NH3/Air flames assisted by non-equilibrium plasma discharge 非平衡等离子体放电辅助下的 NH3/Air 火焰传播特性的数值模拟

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-11-02 DOI: 10.1016/j.combustflame.2024.113809

Qi Zhan, Yangyang Ban, Fan Zhang, Yiqiang Pei, Yanzhao An

Nanosecond non-equilibrium plasma-assisted combustion technology emerges as a reliable novel approach to enhance the flame propagation speed of NH₃. In this study, we developed a zero-dimensional + one-dimensional (0-D+1-D) non-equilibrium plasma-assisted combustion model to investigate the impact of nanosecond pulse discharge on the freely propagating flame speed of NH₃/Air mixture. The results reveal that due to the plasma discharge, abundant intermediate species (N₂H₄, N₂H₃, NO, H₂O₂) are formed at the inlet and are subsequently transported downstream, facilitating flame propagation. As a result, the speed of the 1-D freely propagating flame increases, and the flame front is closer to the inlet compared to the non-plasma condition. The transport effect of H₂ is also evident, with high concentrations of H₂ from the inlet providing the basis for reactions at the flame front that promote combustion. Furthermore, after the initial mixture flows into the flame front, a slight increase in heat release is observed, but this increase occurs within a very limited distance. Notably, in the case of plasma, a stronger heat release is evident at the flame front. Moreover, with plasma, the peaks of OH, H, O, NH₂, and HO₂ are higher and earlier than those of the non-plasma case due to the transport and kinetic effects of plasma. Pathway flux analyses reflect significant changes in the production and consumption paths of the three components OH, H, and O, which are most important for consuming NH₃ due to plasma addition. The higher OH mass fraction promotes the chain reactions that consume NH₃, effectively enhancing the flame propagation speed.

Novelty and significance statement

This study introduces a novel 0-D+1-D nanosecond non-equilibrium plasma-assisted combustion model to examine the impact of nanosecond pulse discharge on NH₃/Air flame propagation. It uniquely analyzes the interaction between species at the inlet and flame front, highlighting the transport effects of plasma-generated intermediates (N₂H₄, N₂H₃, NO, H₂O₂, H₂) that enhance flame speed, with a detailed pathway analysis of key species (O, OH, H).

纳秒非平衡等离子体辅助燃烧技术是提高 NH3 火焰传播速度的可靠新方法。本研究建立了零维+一维（0-D+1-D）非平衡等离子体辅助燃烧模型，以研究纳秒脉冲放电对 NH3/Air 混合气自由传播火焰速度的影响。结果表明，由于等离子体放电，在入口处形成了丰富的中间物种（N2H4、N2H3、NO、H2O2），并随后向下游输送，促进了火焰的传播。因此，一维自由传播火焰的速度增加，与非等离子条件相比，火焰前沿更靠近入口。H2 的传输效应也很明显，来自入口的高浓度 H2 为火焰前沿的反应提供了基础，从而促进了燃烧。此外，在初始混合物流入火焰前沿后，观察到热量释放略有增加，但增加的距离非常有限。值得注意的是，在等离子体的情况下，火焰前沿的热量释放明显更强。此外，在等离子体情况下，由于等离子体的传输和动力学效应，OH、H、O、NH2 和 HO2 的峰值比非等离子体情况下的峰值更高、更早。路径通量分析表明，由于等离子体的加入，对消耗 NH3 最重要的 OH、H 和 O 三种成分的产生和消耗路径发生了显著变化。较高的 OH 质量分数促进了消耗 NH3 的链式反应，有效地提高了火焰的传播速度。它独特地分析了入口和火焰前沿的物种之间的相互作用，突出了等离子体产生的中间产物（N2H4、N2H3、NO、H2O2、H2）的传输效应，这些中间产物提高了火焰速度，并对关键物种（O、OH、H）进行了详细的路径分析。

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引用次数: 0

Dynamic interaction patterns of oblique detonation waves with boundary layers in hypersonic reactive flows 高超音速反应流中斜向爆轰波与边界层的动态相互作用模式

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-11-02 DOI: 10.1016/j.combustflame.2024.113832

Jie Sun , Pengfei Yang , Zheng Chen

Due to their high thermal cycle efficiency and compact combustor, oblique detonation engines hold great promise for hypersonic propulsion. Previous numerical simulations of oblique detonation waves have predominantly solved the Euler equations, disregarding the influence of viscosity and boundary layers. This work aims to study how the interaction between the oblique detonation wave and the boundary layer influences the detonation wave structures in confined spaces. Two-dimensional numerical simulations considering detailed chemistry are performed in a stoichiometric H₂/air mixture. The results indicate that the wedge-induced oblique detonation wave generates a strong adverse pressure gradient upon impacting the upper wall, leading to boundary layer separation. The separation zone subsequently induces an oblique shock wave near the upper wall, and an increase in separation angle will cause the transition from an oblique shock wave to an oblique detonation wave. The formation of the separation zone reduces the actual flow area and may even lead to flow choking; its obstructive effect is similar to that of the Mach stem in inviscid flow. To establish a connection between the viscous recirculation zone and the inviscid Mach stem, we introduce a dimensionless parameter, η, based on the inviscid assumption. It is defined as the ratio of the inviscid Mach stem height to the channel entrance height. This parameter can be used to identify three wave systems in a viscous flow field: separation shock-dominated wave systems, separation detonation-dominated wave systems, and unstable Mach stem-dominated wave systems. Among these, the appearance of detonation Mach stems leads to flow choking, and the shock-detonation wave system continually moves upstream, ultimately causing the failure of the oblique detonation combustion. The findings of this study provide new insights into the investigation of the influence of viscosity on the flow structure of oblique detonation waves.

由于热循环效率高、燃烧器紧凑，斜爆燃发动机在高超音速推进方面大有可为。以往对斜向爆轰波的数值模拟主要求解欧拉方程，忽略了粘度和边界层的影响。这项工作旨在研究斜向爆轰波与边界层之间的相互作用如何影响密闭空间中的爆轰波结构。在化学计量的 H2/air 混合物中进行了二维数值模拟，考虑了详细的化学成分。结果表明，楔形诱发的斜向爆轰波在冲击上壁时会产生强烈的不利压力梯度，导致边界层分离。分离区随后在上壁附近诱发斜冲击波，分离角的增大将导致斜冲击波向斜爆轰波过渡。分离区的形成减小了实际流动面积，甚至可能导致流动窒息；其阻碍作用类似于无粘性流动中的马赫干流。为了在粘性再循环区和无粘性马赫干流之间建立联系，我们在无粘性假设的基础上引入了一个无量纲参数η。它被定义为无粘性马赫杆高度与通道入口高度之比。该参数可用于识别粘性流场中的三种波系：以分离冲击为主的波系、以分离引爆为主的波系和以不稳定马赫杆为主的波系。其中，起爆马赫茎的出现导致流动窒息，冲击-起爆波系不断向上游移动，最终导致斜向起爆燃烧失败。该研究结果为研究粘度对斜向爆轰波流动结构的影响提供了新的见解。

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引用次数: 0

Comparative study on the characteristics of energy release, decomposition, and combustion between NEPE propellants and HTPB propellants NEPE 推进剂与 HTPB 推进剂能量释放、分解和燃烧特性的比较研究

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-11-02 DOI: 10.1016/j.combustflame.2024.113827

Hui Liu , Fang Wang , Huanhuan Gao , Yukun Chen , Xueqin Liao , Jianzhong Liu

Energy performance is always the primary focus of solid propulsion technology development. This paper investigated the characteristics of the energy release, decomposition, and combustion of two typical propellants (NEPE propellants and HTPB propellants) using NASA-CEA calculations, thermal analysis, and an electric wire ignition combustion system. The decomposition temperature of NG, BTTN, GAP, and CL-20 in NEPE propellants were low. The decomposition products were abundant and the decomposition exotherm was large. It had a strong inhibitory effect on LTD of AP and a strong promotional effect on HTD of AP, resulting in the combination of HTD and LTD of AP into a single peak. The flame brightness of two propellants was obviously improved with pressure increasing, as was the flame expansion area, burning rate, and combustion intensity. The ignition delay time t_i decreased and the burning rate r increased. Compared to HTPB propellants, NEPE propellants had brighter flames, larger flame expansion area, more intense combustion, smaller t_i, and smaller r under the same pressure. The pressure exponent n of NEPE propellants (0.43) was larger than that of HTPB propellants (0.39). The rate of the chemical reactions and the rate of diffusion and mixing had a greater impact on the burning rate of NEPE propellants.

能量性能始终是固体推进技术发展的首要关注点。本文利用 NASA-CEA 计算、热分析和电线点火燃烧系统研究了两种典型推进剂（NEPE 推进剂和 HTPB 推进剂）的能量释放、分解和燃烧特性。NEPE 推进剂中 NG、BTTN、GAP 和 CL-20 的分解温度较低。分解产物丰富，分解放热大。对 AP 的 LTD 有很强的抑制作用，对 AP 的 HTD 有很强的促进作用，导致 AP 的 HTD 和 LTD 合并为一个峰。随着压力的增加，两种推进剂的火焰亮度明显提高，火焰膨胀面积、燃烧速率和燃烧强度也明显提高。点火延迟时间 ti 减小，燃烧速率 r 增加。与 HTPB 推进剂相比，在相同压力下，NEPE 推进剂的火焰亮度更高、火焰膨胀面积更大、燃烧更剧烈、ti 更小、r 更小。NEPE 推进剂的压力指数 n（0.43）大于 HTPB 推进剂的压力指数 n（0.39）。化学反应速率以及扩散和混合速率对 NEPE 推进剂燃烧速率的影响更大。

{"title":"Comparative study on the characteristics of energy release, decomposition, and combustion between NEPE propellants and HTPB propellants","authors":"Hui Liu , Fang Wang , Huanhuan Gao , Yukun Chen , Xueqin Liao , Jianzhong Liu","doi":"10.1016/j.combustflame.2024.113827","DOIUrl":"10.1016/j.combustflame.2024.113827","url":null,"abstract":"<div><div>Energy performance is always the primary focus of solid propulsion technology development. This paper investigated the characteristics of the energy release, decomposition, and combustion of two typical propellants (NEPE propellants and HTPB propellants) using NASA-CEA calculations, thermal analysis, and an electric wire ignition combustion system. The decomposition temperature of NG, BTTN, GAP, and CL-20 in NEPE propellants were low. The decomposition products were abundant and the decomposition exotherm was large. It had a strong inhibitory effect on LTD of AP and a strong promotional effect on HTD of AP, resulting in the combination of HTD and LTD of AP into a single peak. The flame brightness of two propellants was obviously improved with pressure increasing, as was the flame expansion area, burning rate, and combustion intensity. The ignition delay time <em>t</em><sub>i</sub> decreased and the burning rate <em>r</em> increased. Compared to HTPB propellants, NEPE propellants had brighter flames, larger flame expansion area, more intense combustion, smaller <em>t</em><sub>i,</sub> and smaller <em>r</em> under the same pressure. The pressure exponent n of NEPE propellants (0.43) was larger than that of HTPB propellants (0.39). The rate of the chemical reactions and the rate of diffusion and mixing had a greater impact on the burning rate of NEPE propellants.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"271 ","pages":"Article 113827"},"PeriodicalIF":5.8,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142571921","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

Theoretical kinetics study of hydrogen abstraction reactions of O2(X3Σg/a1Δg) + CnH2n+2 (n ≤ 4) O2(X3Σg/a1Δg) + CnH2n+2 (n ≤ 4) 取氢反应的理论动力学研究

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-11-01 DOI: 10.1016/j.combustflame.2024.113812

Jie Chen , Qi Chen , Nan Liu , Shanshan Ruan , Xianwu Jiang , Lidong Zhang

The chain-initial reactions of small-molecule alkane (C_nH_2n+2(n ≤ 4)) oxidation participated by electronically excited oxygen O₂(a¹Δg) are crucial for understanding the role of O₂(a¹Δ_g) in plasma-assisted combustion and fuel reforming. Accordingly, in the present work, the energy barriers for the reactions O₂(X³Σ_g/a¹Δg) + alkane (n ≤ 4) → products were investigated by using high-precision quantum calculations. Rate constants for each reaction channel within the temperature range of 300–1500 K were predicted based on transition state theory (TST), supplementing plasma kinetics parameters. The energy barriers and rate constants for methane and ethane oxidation dehydrogenation reactions showed good agreement with literature data, validating the accuracy of the computational method employed in this work. The calculations revealed that the dehydrogenation sites have vital impacts on the reaction system. The energy barriers of the reaction channels involved in O₂(a¹Δ_g) were reduced at different dehydrogenation sites. Specifically, the change rate of each reaction energy barrier at primary, secondary and tertiary site was about 40 %, 65 % and 65 %, respectively. The reactions involving O₂(a¹Δ_g) significantly increased the reaction rate coefficient, especially for single hydrogen abstraction at the secondary and tertiary sites. The effect of O₂(a¹Δ_g) on ignition promotion and its regularity were further studied through kinetic simulations. The results suggested that adding O₂(a¹Δ_g) reduces the ignition delay time (IDT) of small molecular alkanes by approximately one order of magnitude, attributed to variations in energy barrier and branching ratios of different reaction channels. Notably, the H-atom abstraction reaction on primary site showed the largest sensitivity in IDT at 800 K, particularly for propane and isobutane, with IDT change rates of 98.0 % and 96.3 %, respectively. This study provided reasonable rate coefficients for kinetic modeling of plasma-assisted alkane ignition.

电子激发氧 O2(a1Δg)参与的小分子烷烃（CnH2n+2(n≤4)）氧化链初始反应对于理解 O2(a1Δg)在等离子体辅助燃烧和燃料重整中的作用至关重要。因此，本研究利用高精度量子计算研究了 O2(X3Σg/a1Δg) + 烷烃（n ≤ 4）→产物反应的能垒。根据过渡态理论（TST），辅以等离子体动力学参数，预测了 300-1500 K 温度范围内各反应通道的速率常数。甲烷和乙烷氧化脱氢反应的能障和速率常数与文献数据显示出良好的一致性，验证了本研究采用的计算方法的准确性。计算结果表明，脱氢位点对反应体系有重要影响。在不同的脱氢位点，O2(a1Δg)所涉及的反应通道的能量势垒都有所降低。具体来说，在一级、二级和三级位点，各反应能垒的变化率分别约为 40%、65% 和 65%。有 O2(a1Δg) 参与的反应明显提高了反应速率系数，尤其是二级和三级位点的单次取氢反应。通过动力学模拟进一步研究了 O2(a1Δg) 对点火促进的影响及其规律性。结果表明，添加 O2(a1Δg) 可将小分子烷烃的点火延迟时间（IDT）缩短约一个数量级，这归因于不同反应通道的能障和支化比的变化。值得注意的是，初级位点上的 H 原子抽离反应对 800 K 时的 IDT 显示出最大的敏感性，尤其是对丙烷和异丁烷，IDT 变化率分别为 98.0 % 和 96.3 %。这项研究为等离子体辅助烷烃点火的动力学建模提供了合理的速率系数。

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引用次数: 0

Mapping the performance envelope and energy pathways of plasma-assisted ignition across combustion environments 绘制等离子体辅助点火在不同燃烧环境下的性能包络线和能量路径图

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-10-31 DOI: 10.1016/j.combustflame.2024.113793

Raphael J. Dijoud , Nicholas Laws , Carmen Guerra-Garcia

<div><div>Nanosecond pulsed plasmas have been demonstrated, both experimentally and numerically, to be beneficial for ignition, mainly through gas heating (at different timescales) and radical seeding. However, most studies focus on specific gas conditions, and little work has been done to understand how plasma performance is affected by fuel and oxygen content, at different gas temperatures and deposited energies. This is relevant to map the performance envelope of plasma-assisted combustion across different regimes, spanning from fuel-lean to fuel-rich operation, as well as oxygen-rich to oxygen-vitiated conditions, of interest to different industries. This work presents a computational effort to address a large parametric exploration of combustion environments and map out the actuation authority of plasmas under different conditions. The work uses a zero-dimensional plasma-combustion kinetics solver developed in-house to study the ignition of <span><math><mrow><msub><mrow><mi>CH</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>/</mo><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>/</mo><msub><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> mixtures with plasma assistance. A main contribution of the study is the detailed tracking of the energy, from the electrical input all the way to the thermal and kinetic effects that result in combustion enhancement. This extends prior works that focus on the first step of the energy transfer: from the electrical input to the electron-impact processes. Independent of the composition, four pathways stand out: (i) vibrational-translational relaxation, (ii) fast gas heating, (iii) <span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> dissociation, and (iv) <span><math><msub><mrow><mi>CH</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span> dissociation. Results show that the activated energy pathways are highly dependent on gas state, composition, and pulse shape, and can explain the observed range in performance regarding ignition enhancement. The approach can be used to calculate the fractional energy deposition into the main pathways for any mixture or composition, including new fuels, and can be a valuable tool to construct phenomenological models of the plasma across combustion environments.</div><div><strong>Novelty and significance statement</strong></div><div>This work maps the performance of plasma-assisted ignition over a broader range of combustion environments than prior works. Whereas most works focus on fuel/air mixtures, this work quantifies the impact of fuel content and oxygen dilution on plasma actuation. This is relevant to determine the possibilities of using plasma ignition across industries. The novelty of the model presented is the accurate tracking of the energy deposited by the plasma and the identification of the chemical pathways activated by the plasma. Although it is recognized as critical in the description of

纳秒脉冲等离子体主要通过气体加热（在不同的时间尺度上）和自由基播种，在实验和数值上都被证明有利于点火。然而，大多数研究都集中在特定的气体条件上，很少有人去了解在不同的气体温度和沉积能量下，等离子体的性能如何受到燃料和氧气含量的影响。这与绘制等离子体辅助燃烧在不同工况下的性能包络线息息相关，这些工况包括从无燃料到富含燃料的操作，以及从富含氧气到氧气活化的条件，涉及不同行业的利益。本研究通过计算，对燃烧环境进行了大量参数化探索，并绘制出不同条件下等离子体的驱动权限图。这项工作使用内部开发的零维等离子体燃烧动力学求解器，研究等离子体辅助下 CH4/O2/N2 混合物的点火。这项研究的主要贡献在于对能量的详细跟踪，从电输入一直到导致燃烧增强的热效应和动力学效应。这扩展了之前的研究，之前的研究主要关注能量传递的第一步：从电输入到电子撞击过程。与成分无关，有四种途径比较突出：(i) 振动-翻译弛豫，(ii) 快速气体加热，(iii) O2 解离，以及 (iv) CH4 解离。结果表明，激活的能量途径高度依赖于气体状态、成分和脉冲形状，并能解释所观察到的点火增强性能范围。该方法可用于计算任何混合物或成分（包括新燃料）在主要途径中的能量沉积分数，是构建等离子体跨燃烧环境现象学模型的重要工具。大多数研究侧重于燃料/空气混合物，而本研究则量化了燃料含量和氧气稀释对等离子体启动的影响。这对于确定各行业使用等离子点火的可能性具有重要意义。该模型的新颖之处在于准确跟踪了等离子体沉积的能量，并确定了等离子体激活的化学途径。尽管在描述等离子体与气体的相互作用时，详细的能量跟踪被认为是至关重要的，但在等离子体化学模拟中却经常被忽略。在这项工作中，我们提出了一种适用于任何等离子体化学动力学模型的方法，可以在多个时间尺度上分析能量份额。

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引用次数: 0

An experimental and kinetic study of quadricyclane autoignition at high temperatures 高温下四环烷自燃的实验和动力学研究

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-10-31 DOI: 10.1016/j.combustflame.2024.113813

Yuting Ye , Jianbing Cai , Wenbin Tang , Yiwei Li , Dongxian Li , Xu Li , Meng Xu , Changhua Zhang , Jijun Zou , Chuanfeng Yue , Jingbo Wang

Quadricyclane, with high density and net heat value, can provide more energy to extend the flight distance and enhance the payload capacity of aircraft. The autoignition characteristics of quadricyclane have been investigated behind reflected shock waves in this study. With argon as the diluent gas, experiments are conducted at pressures of 2, 4, and 10 atm, equivalence ratios of 0.5, 1.0, and 2.0, fuel concentrations of 0.2% and 0.4%, and temperatures ranging from 1276 to 1773 K. The results indicate that the ignition delay time decreases with increasing pressure and fuel concentration, and increases with increasing equivalence ratio, showing a strong positive dependence with the equivalence ratio. Regression analysis of the experimental data has yielded quantitative relationships. To clarify the combustion process, a high-temperature kinetic model based on the NUIGMech1.1 mechanism has been developed, and the validation demonstrates that the model can accurately describe the autoignition characteristics of quadricyclane. Sensitivity and reaction pathways analyses have been conducted, the results reveal that quadricyclane primarily undergoes ring-opening isomerization to produce 2,5-norbornadiene at high temperature. Furthermore, to demonstrate the effect of the strained structure on fuel ignition, the ignition delay times of quadricyclane/air mixture are measured within a temperature range from 952 to 1113 K, pressure of 10 atm, and equivalence ratio of 1.0. When compared with the ignition delay times of JP-10 and Jet A, quadricyclane exhibits the shortest ignition delay time due to its exothermic ring-opening reaction occurring at the initial stage.

四环烷密度大、净热值高，可提供更多能量，延长飞行距离，提高飞机的有效载荷能力。本研究在反射冲击波后研究了四环烷的自燃特性。实验以氩气为稀释气体，压力分别为 2、4 和 10 atm，当量比分别为 0.5、1.0 和 2.0，燃料浓度分别为 0.2% 和 0.4%，温度范围为 1276 至 1773 K。对实验数据的回归分析得出了定量关系。为阐明燃烧过程，建立了基于 NUIGMech1.1 机理的高温动力学模型，验证表明该模型能准确描述四环烷的自燃特性。研究还进行了灵敏度和反应途径分析，结果表明四环烷在高温下主要发生开环异构化生成 2,5-降冰片二烯。此外，为了证明应变结构对燃料点火的影响，在温度为 952 至 1113 K、压力为 10 atm、当量比为 1.0 的范围内测量了四环烷/空气混合物的点火延迟时间。与 JP-10 和 Jet A 的点火延迟时间相比，四环烷的点火延迟时间最短，这是因为它在初始阶段发生了放热开环反应。

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引用次数: 0

Spatial distribution and temporal evolution of wall-stabilized DME/O2 premixed cool flames 壁面稳定的二甲醚/氧气预混合冷火焰的空间分布和时间演变

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-10-31 DOI: 10.1016/j.combustflame.2024.113814

Meng Zhou , Minhyeok Lee , Yiguang Ju , Yuji Suzuki

The low-temperature oxidation of dimethyl ether (DME) was investigated in premixed wall-stabilized cool flames at two equivalence ratios (ϕ) of 0.2 and 0.5. Using a time-of-flight mass spectrometry (TOF-MS) coupled with gas chromatography (GC), the spatial distributions of major intermediate species, including DME, CH₂O (formaldehyde), CO, CO₂, and CH₃OCHO (methyl formate), were quantified under well-controlled boundary conditions. Moreover, the temporal evolutions of multiple intermediate species in the wall-stabilized cool flame ignition process were measured via TOF-MS, while the wall temperature was gradually ramped up from 550 K to 730 K. Several kinetic models were examined herein to assess the estimated low-temperature reactivity of DME by comparing the one-dimensional axisymmetric simulation results with the experimental data. Wall-stabilized cool flame structures at equivalence ratios ϕ of 0.2 and 0.5 were quantitatively examined with the major intermediate species. It is found that the kinetic models reasonably predict the onset of the reaction zone near the wall. Among these models, Kurimoto et al.’s model gives better predictions for the distributions of CH₂O and CO, which are characteristic species of cool flames. In addition, time-resolved measurements of the unsteady cool flames identified the negative temperature coefficient (NTC) turnover points for different species across various temperature regions. It is also found that the Kurimoto et al. model still indicates a slightly higher reactivity of DME in the low-temperature range, resulting in earlier DME consumption and a shift of NTC window to lower temperatures at ϕ = 0.2.

研究了二甲醚（DME）在 0.2 和 0.5 两种当量比（j）的预混合壁稳定冷焰中的低温氧化过程。利用飞行时间质谱（TOF-MS）与气相色谱（GC）联用技术，在控制良好的边界条件下对主要中间产物（包括二甲醚、CH2O（甲醛）、CO、CO2 和 CH3OCHO（甲酸甲酯））的空间分布进行了量化。此外，在壁面温度从 550 K 逐渐升高到 730 K 的过程中，通过 TOF-MS 测量了壁面稳定冷焰点火过程中多种中间产物的时间演变。对等效比 ϕ 为 0.2 和 0.5 时的壁稳定冷焰结构和主要中间产物进行了定量研究。结果发现，动力学模型合理地预测了反应区在靠近壁面处的开始。在这些模型中，Kurimoto 等人的模型更好地预测了 CH2O 和 CO 的分布，而这两种物质是冷火焰的特征物种。此外，对非稳定冷焰的时间分辨测量确定了不同温度区域内不同物种的负温度系数（NTC）转换点。研究还发现，Kurimoto 等人的模型仍然表明二甲醚在低温范围内的反应活性略高，从而导致二甲醚的提前消耗，并使负温度系数窗口在 ϕ = 0.2 时向低温移动。

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引用次数: 0

Premixed flame behaviors of H2/CH4/C3H8 mixtures in a narrow-gap disk burner and effective Lewis numbers 窄间隙盘式燃烧器中 H2/CH4/C3H8 混合物的预混合火焰行为和有效路易斯数

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-10-29 DOI: 10.1016/j.combustflame.2024.113799

Sang Min Lee, Nam Il Kim

Hydrogen combustion is receiving significant interest as a carbon-free energy resource. However, the distinctive combustion characteristics of hydrogen have yet to be explored sufficiently. This study experimentally investigated the effects of hydrogen blending with methane and propane using a narrow-gap disk burner (NGDB). Three representative flame characteristics were considered: the quenching distance, the flame propagation velocity, and the number of cellular structures. It was confirmed that the quenching Peclet number and the number of cellular structures were significantly affected by the addition of hydrogen, primarily due to the Lewis number. However, defining the Lewis number was somewhat ambiguous, especially for multi-component fuel mixtures. Although various effective Lewis numbers have been suggested, their reliability must be adequately assessed. Six representative Lewis numbers were evaluated based on previous studies, and their correlations with flame characteristics were discussed. Conclusively, the previous Lewis numbers were only partly acceptable and had some exceptions. Therefore, a revised effective Lewis number for the hydrogen-blended flames was suggested, using the maximum laminar burning velocity as a new criterion for determining the deficient species, which showed improved correlations with representative flame propagation characteristics.

氢气燃烧作为一种无碳能源，正受到人们的极大关注。然而，氢气的独特燃烧特性仍有待充分探索。本研究使用窄间隙盘式燃烧器（NGDB）对氢气与甲烷和丙烷混合的效果进行了实验研究。研究考虑了三种具有代表性的火焰特征：淬火距离、火焰传播速度和蜂窝结构数量。研究证实，淬火佩克莱特数和蜂窝状结构数量受氢气添加的影响很大，这主要是由于路易斯数的影响。然而，路易斯数的定义有些模糊，特别是对于多组分燃料混合物。虽然已经提出了各种有效的路易斯数，但必须对其可靠性进行充分评估。根据之前的研究，我们评估了六个具有代表性的路易斯数，并讨论了它们与火焰特性的相关性。结果表明，以前的路易斯数只有部分是可以接受的，而且有一些例外情况。因此，针对氢气混合火焰提出了经修订的有效路易斯数，使用最大层流燃烧速度作为确定不足种类的新标准，该路易斯数与代表性火焰传播特性的相关性得到了改善。

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引用次数: 0

Revealing the oxidation kinetics of n-dodecane, ethylcyclohexane and n-butylbenzene blended fuels 揭示正十二烷、乙基环己烷和正丁基苯混合燃料的氧化动力学

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame

Pub Date : 2024-10-28 DOI: 10.1016/j.combustflame.2024.113806

Meirong Zeng , Jigang Gao , Yuwen Deng , Peiqi Liu , Zhongyue Zhou , Jiuzhong Yang , Wenhao Yuan , Fei Qi

The oxidation chemistry of single component has been widely explored, which motivates us to investigate the oxidation chemistry of blended fuels. Here, n-dodecane, ethylcyclohexane and n-butylbenzene have been selected as fuel components for representing n-alkane, cyclic alkane and aromatic, respectively. The oxidation experiments of blended n-dodecane, ethylcyclohexane and n-butylbenzene fuels were performed in an atmospheric jet stirred reactor, temperatures ranging from 450 to 850 K, equivalence ratios of 0.5 and 1.0. The synchrotron vacuum ultraviolet radiation photoionization mass spectrometry was applied to measure the featured intermediates, such as hydroperoxides and highly oxygenated molecules (HOMs) with characteristic functional groups. Subsequently, a kinetic model for the blended fuels was developed and validated, which was used to reveal the crucial coupled oxidation chemistry that drives the global oxidation reactivity and products distribution. It is revealed that the active chain initiators, such as OH radicals, produced by the oxidation reactions of n-dodecane and ethylcyclohexane, significantly enhance the oxidation reactivity of n-butylbenzene. Furthermore, the hydroperoxides and ketohydroperoxides, acting as key experimental evidence for the existence of first O₂ addition and second O₂ addition, contribute to the formation of active chain initiators, such as OH radicals. This work extends the existing conceptual reaction schemes proposed for the oxidation of single fuel towards the coupled oxidation chemistry of blended fuels. This, in turn, improves our understanding towards the complicated oxidation chemistry of real fuels.

单一成分的氧化化学性质已被广泛探讨，这促使我们研究混合燃料的氧化化学性质。本文选择正十二烷、乙基环己烷和正丁基苯作为燃料组分，分别代表正烷烃、环烷烃和芳烃。正十二烷、乙基环己烷和正丁基苯混合燃料的氧化实验在常压喷射搅拌反应器中进行，温度范围为 450 至 850 K，当量比为 0.5 和 1.0。同步辐射真空紫外辐射光离子化质谱法用于测量特征中间产物，如氢过氧化物和具有特征官能团的高含氧分子（HOMs）。随后，开发并验证了混合燃料的动力学模型，该模型用于揭示驱动全局氧化反应性和产物分布的关键耦合氧化化学反应。研究发现，正十二烷和乙基环己烷氧化反应产生的活性链引发剂（如羟基自由基）可显著提高正丁基苯的氧化反应性。此外，氢过氧化物和酮氢过氧化物是第一次 O2 加成和第二次 O2 加成存在的关键实验证据，有助于形成活性链引发剂，如 OH 自由基。这项工作将现有的单一燃料氧化概念反应方案扩展到混合燃料的耦合氧化化学反应。这反过来又加深了我们对实际燃料复杂氧化化学反应的理解。

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引用次数: 0