这些实验是在德国斯图加特的燃烧技术研究所、德意志姆霍兹 Luft Raumfahrt (DLR) 的质谱学系进行的。这项工作还得到了亥姆霍兹能源联盟 "合成液态烃"、卓越中心 "替代燃料" 和 DLR 项目 "未来燃料" 的支持。作者希望感谢帕特里克乐 Clercq 和他在喷气燃料方面卓有成效的讨论。

1. 分子束质谱仪 (MBMS) 和流化反应器系统的建立
<ol><li>加热烤箱到指定的起始温度, 这是最高温度在指定的测量系列。对于射流 A-1 与Φ = 1 的典型条件, 总氧化低于850°c (~ 1100 K)。适当的起动温度的选择取决于被调查的燃料的化学性质和计量 (Φ)。</li>
	<li>为中间物种检测准备飞行时间测量光谱仪。该谱仪与分子束对齐, 从而为不稳定物种提供可靠的检测。 注: 质量分辨率适用于 C/小时系统中元素组成的测定。为了避免碎片, 选择了软电离条件。典型的9.5 到 10.5 eV 的值已经被证明适合于对燃烧中间物进行的一个一般的研究。</li>
	<li>为主要物种的检测准备四极光谱仪。 注: 由于四极光谱仪 (也称为残余气体分析仪, RGA) 放置在分子束附近的 MBMS 系统的电离室内, 仅测量壁散射的背景气体。由于主要物种稳定, 背景压力很好地反映了它们在取样尖端的浓度。为了更好的信噪比, 选择了高电离能 70 eV 在这种情况下。</li>
</ol>2. 燃料样品的制备
<ol><li>准备用于燃料供应的金属注射器。 警告:使用适当的个人防护设备进行燃料处理。<ol>
<li>填充30毫升的燃料样品蒸发器金属注射器。</li>
		<li>增压燃油供应系统 (金属注射器) 高达5巴通过增加增压空气到系统, 虽然打开阀门。</li>
		<li>排气燃料线和科里奥利质量流量计通过打开在燃料供应线的阀门。</li>
	</ol>
</li>
	<li>加热蒸发器和供气线。在给定的设置中, 温度远远低于正常压力沸点, 可以应用由于高稀释。确保燃料的最高沸腾化合物的指定温度下的蒸气压高于其在气流中的分压。通常, 200 °c 是足够的喷气 A-1。</li>
	<li>请注意, 系统中最冷的点是回火进口法兰到烤箱。确保稀释的燃料在这个地方不能 recondense。对于典型的喷气 A-1 (99% 稀释) 设置水冷却系统到80°c 是充足的。</li>
</ol>3. 测量和数据采集
<ol><li>将烤箱置于取样位置。取样锥必须放在烤箱的陶瓷管内。在本实验中, 取样位置接近烘箱空间温度剖面的高原值。 注意:图 1中的图片显示了锥和反应器。加热的反应器 (蓝色) 在路轨移动对石英锥体。</li>
	<li>通过科里奥利质量流量计添加气体, 开始选择稀释剂。 注: 质量流量表由原软件包控制。在这里, 可以设置质量流值。通常, 使用99% 氩。一般而言, 对于液体燃料, 稀释剂的流动可能被分解为气化器和氧化剂气体流通过使用一个额外的科里奥利质量流量计平行的 Cori 流2通过加热线和直接连接到氧化剂流从 Cori 流3。</li>
	<li>使用指定的工具软件开始连续的数据记录 (飞行和四极)。 注: 单击四极软件中的 "启动" 按钮。单击 "飞行软件" 中的 "启动" 按钮。<ol>
<li>通过设置科里奥利流量计软件的适当流程条件, 添加氧化剂 O2 。观察传入氧化剂作为新的峰值在质谱。</li>
	</ol>
</li>
	<li>通过设置科里奥利质量流量计的适当流量条件来添加燃料。<ol>
<li>检查光谱。如果在精益和化学计量条件下实现了完全氧化, 请观察稳定 CO2质量信号。</li>
	</ol>
</li>
	<li>当信号强度稳定为4到5测量时, 稳定周期结束。稳定期后, 将-200 克/小时的连续温度衰减坡道应用于烤箱。这导致典型的测量时间 2 h 每测量奔跑。<ol>
<li>在一个特定的烤箱温度的斜坡, 观察一个快速变化的质谱。单一燃烧产品 (H2O, co2和 co, H2在富有的情况下) 开始消失, 并且小燃烧中间体变得可检测。 注意: 随着温度的进一步降低, 可见中间体变得越来越大。在冷烘箱温度下, 仅能观察到燃料化合物和氧气的信号;在反应堆的当前居住时间内没有发生反应。</li>
	</ol>
</li>
	<li>当最终温度稳定时 (通常为500摄氏度; 10 分钟), 关掉氧化剂。<ol>
<li>继续记录测量。在没有氧化剂的情况下获得燃料特性 (碎片组成) 测量。</li>
	</ol>
</li>
	<li>通过将该值设置为 0, 将科里奥利质量流量计软件中的燃料关掉。数据仍将记录在案;使用这些光谱进行背景测量。</li>
	<li>通过单击软件中的 "停止" 按钮停止数据录制。</li>
</ol>4. 校准测量
<ol><li>对于校准问题, 在取样锥前安装一个闭合腔。 注: 封闭室是一管, 它是放置在喷嘴前面的手。</li>
	<li>打开阀门泵。密室被疏散了</li>
	<li>应用二进制混合物 (兴趣和 Ar 的碳氢化合物) 或商用校准气体校准。为示范, 在这里使用 co 和 co2和氩的定制的气体混合物。</li>
	<li>通过针阀调整校准腔内的压力, 以获得高于信噪比和饱和极限下的信号强度。</li>
	<li>通过单击飞行软件中的 "开始" 按钮, 开始校准测量, 方法是在3.5 中为单个测量执行数据记录。</li>
</ol>5. 数据处理
注: 重新编码光谱必须与所记录的各自的烘箱温度相匹配。
<ol><li>在每一个记录的温度, 对于每个选定的物种, 计算其摩尔分数从相应的信号。绘制摩尔分数配置文件与烤箱温度 (图 3)。</li>
</ol>

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Flame. 166, 255-265 (2016).</li><li>Hansen, N., Skeen, S. A., Michelsen, H. A., Wilson, K. R., Kohse-Hoinghaus, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flame+experiments+at+the+advanced+light+source:+new+insights+into+soot+formation+processes.">Flame experiments at the advanced light source: new insights into soot formation processes.</a> J Vis Exp. (87), e51369 (2014).</li><li>Qi, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isomeric+identification+of+polycyclic+aromatic+hydrocarbons+formed+in+combustion+with+tunable+vacuum+ultraviolet+photoionization.">Isomeric identification of polycyclic aromatic hydrocarbons formed in combustion with tunable vacuum ultraviolet photoionization.</a> Rev Sci Instum. 77 (8), 084101 (2006).</li><li>Hansen, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2D-imaging+of+sampling-probe+perturbations+in+laminar+premixed+flames+using+Kr+X-ray+fluorescence.">2D-imaging of sampling-probe perturbations in laminar premixed flames using Kr X-ray fluorescence.</a> Combust. Flame. 181, 214-224 (2017).</li></ol>

作者没有什么可透露的。

将大气高温流反应器与分子束质谱检测系统相结合, 使各种操作条件下的定量形态数据得以实现。几项研究21,22,23,27显示实验的灵活性从与部分氧化现象相关的丰富的甲烷条件开始 (φ = 2.5), 调查现代喷气燃料化合物如 farnesane 的燃烧化学。这样的研究使动能反应建模能够覆盖更多的技术领域,如?...

从可再生资源的现代低排放燃料中了解燃烧过程对当今社会的生态和经济议题是一个挑战。它们有可能减少我们对矿物燃料的依赖, 抵消 CO2排放量, 并对有害污染物排放 (如烟尘及其毒性前体1) 产生积极影响。将这个快速增长的领域与它们在现代燃烧室系统中的应用结合起来, 对控制化学和物理过程的基本理解的需求大大增加了2。即使在今天, 由于基链反应而产生的复杂化学反应网络仍然没有得到充分的理解。为了分析甚至控制污染物形成或 (自动) 点火过程等现象, 化学反应网络的详细知识是拼图3的关键部分。
为了调查和理解这些化学反应网络, 实验和数值方法是强制性的。实验中, 燃烧化学通常是通过应用简化的和良好的控制流环境的实验来研究特定问题。单个子过程的高复杂性和动态性通过基础实验防止了技术燃烧室条件的精确再现, 同时允许跟踪指定的关键特性, 如温度、压力、热释放, 或化学物种。早期, 对不同的实验方法的需要变得明显, 每个解决一个具体的问题, 并提供了后续的一系列信息, 有助于整个全球的燃烧化学图片。为了涵盖各种条件, 并收集随后的信息集, 以描述技术系统中发生的复杂情况, 成功地开发了多种方法。完善的技术包括:
<ul><li>激波管4,5,6和快速压缩机7。这些设备提供了很大范围内的压力和温度控制。然而, 可接触反应时间和适当的分析技术是有限的。</li>
	<li>层流预混火焰3,8,9,10,11是理想的, 以获得高温条件结合一个简单的流场。由于反应区的空间维数随着压力的增大而减小, 在低压条件下, 预混火焰通常会被研究成形态。</li>
	<li>逆流扩散火焰12,13,14,15是研究湍流燃烧小火焰计算机制的理想选择。它们模拟了由于不均匀性在一个真正的湍流流中的应变, 但在分析形态技术中又受到高度限制。</li>
	<li>各种反应堆实验16、17、18 (静态、搅拌和插头流) 提供了对高压环境的访问, 而温度通常比火焰环境低。常见的方法有:<ul>
<li>静止电抗器广泛用于脉冲光解实验, 但一般受长期停留时间和低温的限制。</li>
		<li>喷射搅拌反应器,即完全搅拌反应器 (PSR) 的气体版本, 依赖于气相的有效混合, 并可在恒定的停留时间、温度和压力下稳定运行, 使模型易于建模。然而, 分子有时间迁移到热表面, 并接受不同的反应。</li>
		<li>许多流动反应器方法是已知的, 与塞式流动反应器 (PFR) 是描述化学反应的最普遍的方法在连续, 流动系统的圆筒几何。在稳定状态下, 采用固定停留时间作为其理想 PFRs 位置的函数来假设插头流条件。</li>
	</ul>
</li>
</ul>在实验燃烧动力学领域有价值的技术的补充, 高温层流反应器实验19,20采用分子束质谱 (MBMS) 技术进行跟踪本文详细介绍了物种开发的21、22 。层流条件, 工作在大气压和可接近的温度到 1800 K 是流动反应器的主要特征, 而敏感 MBMS 技术允许检测几乎所有在燃烧中存在的化学物质过程.这包括高度活性的物种, 如激进分子, 它们不能或几乎无法与其他检测方法进行跟踪。MBMS 技术广泛用于对常规和现代替代燃料火焰中的反应网络进行详细调查, 如醇类或醚23,24,25 , 并已证明是对现代动力学模型的发展具有重要意义。
图 1显示了使用取样探针 (a) 缩放帧的高温流反应器的示意图, 以及两张突出显示总体实验 (B) 和探头设置 (C) 的图片。该系统可分为两部分: 一是具有燃气供应和蒸发器系统的高温流反应器, 二是 MBMS 飞行时间检测系统。在运行中, 流管的出口直接安装在 MBMS 系统的取样喷嘴上。气体直接从反应器出口取样, 转移到高真空检测系统。在这里, 电离是通过电子电离和随后的飞行时间检测进行的。
该反应器有一个40毫米内径陶瓷 (Al2O3) 管的1497毫米长度放置在一个高温烤箱 (, Gero, 类型 HTRH 40-1000).总加热段长度为1000毫米。气体被预混, 并预先汽化进入反应器由一个回火法兰 (通常回火到 ~ 80 °c)。高度稀释 (约99体积% 在 Ar), 层流流动反应物混合物通过已知的温度剖面 (详细的温度特性将在下面给出)。气体组分的检测发生在反应器出口作为烤箱温度的作用。测量是在恒定的入口质量流, 而单调下降温度斜坡 (-200 k/小时) 适用于烤箱的范围内 1800 k 到 600 k 注意到, 当测量不同的温度时, 可能会取得类似的结果。等温烘箱温度和热惯性被认为是正确的。该系统的热稳定性仍需一段时间, 选择温度坡道作为平均时间的折衷 (可忽略) 小温度增量和每系列总测量时间。平均时间 (四十五年代) MBMS 对应于 2.5 K。在给定条件下, 所得到的居住时间约为2秒 (在 1000 K 处)。最后, 由于温度的再现性, 在目前的反应堆实验中, 可以说明±5 K 或更好的测温温度的相对精度。
图 2显示了汽化系统的示意图, 它优化以调查甚至复杂的碳氢化合物混合物, 如技术喷射燃料。所有输入流都以科里奥利质量流量计的高精度 (±0.5%) 计量。燃料的汽化由一个商业蒸发器系统在温度200°c 实现。所有供应线与预汽化燃料的温度通常为150摄氏度, 以防止液体燃料的凝结, 同时避免热降解的同时。完全和稳定的汽化是例行检查, 甚至可能发生在温度低于正常沸点的各自燃料。完全蒸发是由小燃料分数和低分压 (通常低于 100 Pa) 确保所需的。
气体是由一个石英锥在反应堆出口中心线上的环境压力 (约 960 hPa) 取样, 在图 1的缩放框架中更详细地看到。喷嘴尖端有一个50微米的孔, 它位于大约30毫米内的陶瓷管在反应区结束。注意, 取样位置是固定在入口上的。烤箱管的热膨胀只发生在出口, 这是不机械地连接到取样系统导致温度独立长度的反应段。由于分子束的形成, 当气体扩展到高真空 (两个不同的抽运阶段; 10-2和 10-4 Pa)25,26时, 所有反应立即被淬火。该样本被引导到电子撞击时间 (飞行时) 质谱仪 (质量分辨率 R = 3000) 的离子源, 能够根据适当的精度确定现有物种的确切质量, 以确定一个 c-/小时内的元素组成。i/o 系统。电子能量被设置为低值 (通常为 9.5-10.5 eV), 以尽量减少由于电离过程的碎片。注意, 稀释剂和参考种类氩仍然是可检测的由于广泛的能量分布电离电子 (1.4 eV FWHM)。Ar 可以用好的 S/N 来测量, 低电子能量不允许对主要种类 (H2O、co2、co、H2、O2和燃料) 配置文件进行足够的确定, 这些剖面在显著较低浓度下存在。.
除了在飞行中检测外, 一个残留气体分析仪 (RGA),即四极质谱仪, 被放置在电离室中, 以更高的电子能量 (70 eV) 监测上述六种, 同时对 MBMS 的测量。

<table><tbody><tr><td>Time-Of-Flight MBMS</td><td>Kaesdorf</td><td>n.a.</td><td>custom design</td></tr><tr><td>Molecular Beam Samling Interface</td><td>self made</td><td>n.a.</td><td>custom design</td></tr><tr><td>Laminar Flow Reactor</td><td>Gero</td><td>Type HTRH 40-1000</td><td>custom design</td></tr><tr><td>Quadrupole MS</td><td>Hiden</td><td>HAL/3F 301</td><td>adapted to ionization chamber</td></tr><tr><td>Vaporizer</td><td>Bronkhorst</td><td>CEM</td><td>Vaporizer</td></tr><tr><td>Mass Flow Meter</td><td>Bronkhorst</td><td>Mini Cori-Flow M12, M13, M14</td><td>Flow Controller</td></tr><tr><td>Jet A-1</td><td>n.a.</td><td>n.a.</td><td>Standard Jet fuel of interest</td></tr><tr><td>Metal syringe</td><td>Hugo Sachs</td><td>70-2252</td><td>Fuel Supply</td></tr><tr><td>Heating Hoses</td><td>Hillesheim</td><td>HMI series</td><td>Gas Preheating</td></tr><tr><td>Gas</td><td>Linde</td><td>Ar, O2</td><td>Diluent, Oxidizer</td></tr></tbody></table>

combustion chemistry of fuels: quantitative speciation data obtained from an atmospheric high-temperature flow reactor with coupled molecular-beam mass spectrometer

这篇手稿描述了一个高温流反应器实验耦合到强大的分子束质谱 (MBMS) 技术。这个灵活的工具提供了一个详细的观察化学气相动力学的反应流在良好的控制条件。在层流反应器中提供的大量操作条件使我们能够获得特殊的燃烧应用, 而这些应用程序通常不能通过火焰实验实现。这些包括在高温条件下与气化过程有关的丰富环境, 过氧化化学控制低温氧化机制或研究复杂的技术燃料。所提出的设置允许测量的数量形态数据的反应模型验证燃烧, 气化和热解过程, 同时使系统的普遍理解的反应化学。动力学反应模型的验证一般是通过研究纯化合物的燃烧过程来进行的。流化反应器已被加强, 以适合技术燃料 (如喷射 A-1 的多组分混合物), 以允许对发生燃烧中间体如烟尘前体或污染物的现象学分析。实验设计提供的受控和可比较的边界条件可以预测污染物的形成趋势。冷反应物被送入预混进反应器中, 高度稀释 (在 Ar 中约99体积%), 以抑制自我维持的燃烧反应。层流反应物混合物经过已知的温度场, 而气体成分是确定在反应堆排气作为一个功能的烤箱温度。流动反应器在大气压下作以温度 1800 K 。测量本身是通过降低温度单调率为-200 克/小时。利用敏感的 MBMS 技术, 在反应过程中几乎所有的化学物种, 包括激进物种, 都获得和量化了详细的形态数据。

在图 3中显示了取样气体组成的典型质量谱。与给定的质量分辨率约3000的设置, 物种由 m/z = 260, 您可以在 c/c++ 系统中检测到。在质量校准过程中, 峰值被集成为每个质量-电荷 (m-/z) 比和反褶积算法, 以评估未解决的信号。在背景和碎片校正之后, 信号可以用适当的校准因子与已知协作 (典型的惰性气体氩) 的参考物种进行量化。获得校准因子的几个复杂...

Watch this Scientific Journal Video about Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectr

Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer

燃料燃烧化学: 用耦合分子束质谱仪从大气高温流反应器中获得的定量形态数据

通过比较定量形态数据, 对新型生物燃料、燃料组分或喷气燃料的氧化燃烧化学进行了研究。这些数据可用于动态模型验证, 并能够实现燃料评估策略。这篇手稿描述了大气高温流反应器并证明了它的能力。

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This ...

combustion-chemistry-fuels-quantitative-speciation-data-obtained-from

Universidad de Cartagena UDEC

Research

JoVE Journal

Chemistry

10.0K 次观看.  German Aerospace Center (DLR). 通过比较定量形态数据, 对新型生物燃料、燃料组分或喷气燃料的氧化燃烧化学进行了研究。这些数据可用于动态模型验证, 并能够实现燃料评估策略。这篇手稿描述了大气高温流反应器并证明了它的能力。

视频: Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

火焰在实验的先进光源:全新洞察烟灰形成过程

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

科研

工程学

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the balls. Among other applications, it is a versatile technique that allows for effective preparation of gasless reactive nanostructured materials with high energy density per volume (Ni+Al, Ta+C, Ti+C). The structural transformations of reactive media, which take place during HEBM, define the reaction mechanism in the produced energetic&#160;composites. Varying the processing conditions permits fine tuning of the milling-induced microstructures of the fabricated composite particles. In turn, the reactivity, i.e., self-ignition temperature, ignition delay time, as well as reaction kinetics, of high energy density materials depends on its microstructure. Analysis of the milling-induced microstructures suggests that the formation of fresh oxygen-free intimate high surface area contacts between the reagents is responsible for the enhancement of their reactivity. This manifests itself in a reduction of ignition temperature and delay time, an increased rate of chemical reaction, and an overall decrease of the effective activation energy of the reaction. The protocol provides a detailed description for the preparation of reactive nanocomposites with tailored microstructure using short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of the energetic materials. The protocol can be adapted to preparation and characterization of a variety of nanostructured energetic composites.

This protocol describes the preparation of gasless nanostructured energetic materials (Ni+Al, Ta+C, Ti+C) using the short-term high-energy ball milling (HEBM) technique. It also describes a high-speed thermal imaging method to study the reactivity of mechanically fabricated nanocomposites. These protocols can be extended to other reactive nanostructured energetic materials.

准备和无气腹纳米结构的反应含能材料

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

PTR-ToF-MS Coupled with an Automated Sampling System and Tailored Data Analysis for Food Studies: Bioprocess Monitoring, Screening and Nose-space Analysis

Proton Transfer Reaction (PTR), combined with a Time-of-Flight (ToF) Mass Spectrometer (MS) is an analytical approach based on chemical ionization that belongs to the Direct-Injection Mass Spectrometric (DIMS) technologies. These techniques allow the rapid determination of volatile organic compounds (VOCs), assuring high sensitivity and accuracy. In general, PTR-MS requires neither sample preparation nor sample destruction, allowing real time and non-invasive analysis of samples. PTR-MS are exploited in many fields, from environmental and atmospheric chemistry to medical and biological sciences. More recently, we developed a methodology based on coupling PTR-ToF-MS with an automated sampler and tailored data analysis tools, to increase the degree of automation and, consequently, to enhance the potential of the technique. This approach allowed us to monitor bioprocesses (e.g. enzymatic oxidation, alcoholic fermentation), to screen large sample sets (e.g. different origins, entire germoplasms) and to analyze several experimental modes (e.g. different concentrations of a given ingredient, different intensities of a specific technological parameter) in terms of VOC content. Here, we report the experimental protocols exemplifying different possible applications of our methodology: i.e. the detection of VOCs released during lactic acid fermentation of yogurt (on-line bioprocess monitoring), the monitoring of VOCs associated with different apple cultivars (large-scale screening), and the in vivo study of retronasal VOC release during coffee drinking (nosespace analysis).

Proton Transfer Reaction Time of Flight Mass Spectrometry allows high-sensitivity, rapid and non-invasive analysis of volatile organic compounds. To demonstrate its potential, we give three examples: lactic acid fermentation of yogurt (on-line bioprocess monitoring), different apple genotypes (large-scale screening), and retronasal space after drinking coffee (nosespace analysis).

PTR-ToF-MS结合自动采样系统和食品研究定制数据分析:生物过程监测，筛选和鼻空间分析

Proton Transfer Reaction (PTR), combined with a Time-of-Flight (ToF) Mass Spectrometer (MS) is an analytical approach based on chemical ionization that ...

化学

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.

We describe the use of micro-thermocouples to estimate local temperature gradients in steady laminar boundary layer diffusion flames. By extension of the Reynolds Analogy, local temperature gradients can be further used to estimate the local mass burning rates and heat fluxes in such flames with high accuracy.

在稳定层流边界层扩散火焰本地热通量和燃烧率的估计实验方法

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex ...

Combustion Characterization and Model Fuel Development for Micro-tubular Flame-assisted Fuel Cells

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power generation and micro combustion as well as development in fuel cell research has created new means of power generation that combine solid oxide fuel cells with open flames and combustion exhaust. Instead of relying upon the heat of combustion, these solid oxide fuel cell systems rely on reforming of the fuel via combustion to generate syngas for electrochemical power generation. Procedures were developed to assess the combustion by-products under a wide range of conditions. While theoretical and computational procedures have been developed for assessing fuel-rich combustion exhaust in these applications, experimental techniques have also emerged. The experimental procedures often rely upon a gas chromatograph or mass spectrometer analysis of the flame and exhaust to assess the combustion process as a fuel reformer and means of heat generation. The experimental techniques developed in these areas have been applied anew for the development of the micro-tubular flame-assisted fuel cell. The protocol discussed in this work builds on past techniques to specify a procedure for characterizing fuel-rich combustion exhaust and developing a model fuel-rich combustion exhaust for use in flame-assisted fuel cell testing. The development of the procedure and its applications and limitations are discussed.

A protocol for creating a model fuel-rich combustion exhaust is developed through combustion characterization and is applied for micro-tubular flame-assisted fuel cell testing and research.

燃烧特性参数和模型燃料开发的微型管状火焰辅助燃料电池

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power ...

Reaction Kinetics and Combustion Dynamics of I4O9 and Aluminum Mixtures

Tetraiodine nonoxide (I4O9) has been synthesized using a dry approach that combines elemental oxygen and iodine without the introduction of hydrated species. The synthesis approach inhibits the topochemical effect promoting rapid hydration when exposed to the relative humidity of ambient air. This stable, amorphous, nano-particle material was analyzed using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) and showed an exothermic energy release at low temperature (i.e., 180 &#176;C) for the transformation of I4O9 into I2O5. This additional exothermic energy release contributes to an increase in overall reactivity of I4O9 when dry mixed with nano-aluminum (Al) powder, resulting in a minimum of 150% increase in flame speed compared to Al + I2O5. This study shows that as an oxidizer, I4O9 has more reactive potential than other forms of iodine(V) oxide when combined with Al, especially if I4O9 can be passivated to inhibit absorption of water from its surrounding environment.

Reaction Kinetics and Combustion Dynamics of I4O9 and Aluminum Mixtures

A protocol for measuring flame speeds of a reactive mixture composed of tetraiodine nonoxide (I4O9) and aluminum (Al) is presented. A method for resolving reaction kinetics using differential scanning calorimetry (DSC) is also presented. It was found that I4O9 is 150% more reactive than other iodine(V) oxides.

反应动力学和我燃烧动力学<sub&gt; 4</sub&gt; 0<sub&gt; 9</sub&gt;和铝的混合物

Tetraiodine nonoxide (I4O9) has been synthesized using a dry approach that combines elemental oxygen and iodine without the introduction of hydrated ...

Quantitative Analysis by Thermogravimetry-Mass Spectrum Analysis for Reactions with Evolved Gases

During energy conversion, material production, and metallurgy processes, reactions often have the features of unsteadiness, multistep, and multi-intermediates. Thermogravimetry-mass spectrum (TG-MS) is seen as a powerful tool to study reaction features. However, reaction details and reaction mechanics have not been effectively obtained directly from the ion current of TG-MS. Here, we provide a method of an equivalent characteristic spectrum analysis (ECSA) for analyzing the mass spectrum and giving the mass flow rate of reaction gases as precise as possible. The ECSA can effectively separate overlapping ion peaks and then eliminate the mass discrimination and temperature-dependent effect. Two example experiments are presented: (1) the decomposition of CaCO3 with evolved gas of CO2 and the decomposition of hydromagnesite with evolved gas of CO2 and H2O, to evaluate the ECSA on single-component system measurement and (2) the thermal pyrolysis of Zhundong coal with evolved gases of inorganic gases CO, H2, and CO2, and organic gases C2H4, C2H6, C3H8, C6H14, etc., to evaluate the ECSA on multi-component system measurement. Based on the successful calibration of the characteristic spectrum and relative sensitivity of specific gas and the ECSA on mass spectrum, we demonstrate that the ECSA accurately gives the mass flow rates of each evolved gas, including organic or inorganic gases, for not only single but multi-component reactions, which cannot be implemented by the traditional measurements.

Precise determination of the evolved gases&#39; flow rate is key to study the details of reactions. We provide a novel quantitative analysis method of equivalent characteristic spectrum analysis for thermogravimetry-mass spectrum analysis by establishing the calibration system of the characteristic spectrum and relative sensitivity, for obtaining the flow rate.

热重分析-质谱分析对演化气体反应的定量分析

During energy conversion, material production, and metallurgy processes, reactions often have the features of unsteadiness, multistep, and ...

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species in the ppm-to-single-percent range. The main purpose of the method is the spatially resolved detection of low-concentration species, which have no transitions in the visible or near-IR spectral range that could be used for detection. IR-DFWM is a nonintrusive method, which is a great advantage in combustion research, as inserting a probe into a flame can change it drastically. The IR-DFWM is combined with upconversion detection. This detection scheme uses sum-frequency generation to move the IR-DFWM signal from the mid-IR to the near-IR region, to take advantage of the superior noise characteristics of silicon-based detectors. This process also rejects most of the thermal background radiation. The focus of the protocol presented here is on the proper alignment of the IR-DFWM optics and on how to align an intracavity upconversion detection system.

Here, we present a protocol to perform sensitive, spatially resolved gas spectroscopy in the mid-infrared region, using degenerate four-wave mixing combined with upconversion detection.

用于定量气体传感的红外退化四波融合与上转换检测

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species ...

Nitrogen Compound Characterization in Fuels by Multidimensional Gas Chromatography

Certain nitrogen-containing compounds can contribute to fuel instability during storage. Hence, detection and characterization of these compounds is crucial. There are significant challenges to overcome when measuring trace compounds in a complex matrix such as fuels. Background interferences and matrix effects can create limitations to routine analytical instrumentation, such as GC-MS. In order to facilitate specific and quantitative measurements of trace nitrogen compounds in fuels, a nitrogen-specific detector is ideal. In this method, a nitrogen chemiluminescence detector (NCD) is used to detect nitrogen compounds in fuels. NCD utilizes a nitrogen-specific reaction that does not involve the hydrocarbon background. Two-dimensional (GCxGC) gas chromatography is a powerful characterization technique as it provides superior separation capabilities to one-dimensional gas chromatography methods. When GCxGC is paired with a NCD, the problematic nitrogen compounds found in fuels can be extensively characterized without background interference. The method presented in this manuscript details the process for measuring different nitrogen-containing compound classes in fuels with little sample preparation. Overall, this GCxGC-NCD method has been shown to be a valuable tool to enhance the understanding of the chemical composition of nitrogen-containing compounds in fuels and their impact on fuel stability. The % RSD for this method is &#60;5% for intraday and &#60;10% for interday analyses; the LOD is 1.7 ppm and the LOQ is 5.5 ppm.

Here, we present a method utilizing two-dimensional gas chromatography and nitrogen chemiluminescence detection (GCxGC-NCD) to extensively characterize the different classes of nitrogen-containing compounds in diesel and jet fuels.

多维气相色谱在燃料中的氮化合物表征

Certain nitrogen-containing compounds can contribute to fuel instability during storage. Hence, detection and characterization of these compounds is ...

Flame Photometry: Overview

Flame photometry, also known as flame emission spectrometry, is a technique used for the qualitative and quantitative analysis of elements present in a sample using a flame as the source of excitation energy. The concept of flame photometry was realized in the early 1860s by Kirchhoff and Bunsen, who discovered that specific elements emit characteristic radiation when excited in flames. The first instrument developed for this purpose was used to measure sodium (Na) in plant ash using a Bunsen flame. However, the challenge lay in finding the most effective way to introduce the sample into the flame. It wasn&#39;t until 1929, when Lundegardh introduced a nebulizer, that a significant breakthrough was made, allowing a reproducible introduction of the sample into the flame.
In flame emission spectrometry, the nebulizer converts a liquid sample into a fine mist or aerosol. This is achieved by passing a high-pressure gas stream over the end of a capillary tube containing the sample and aspirating it into a spray chamber. The aerosol produced is then passed to the burner, where flame heat desolvates it, forming dry particles that volatilize and produce free atoms for analysis.
Early instruments utilized quartz prism spectrographs and photographic recording to disperse and capture atomic emission lines. However, advancements in optical filters and electrical photodetectors replaced these components, improving precision and convenience.
Flame photometry involves introducing the sample solution into a nebulizer, which converts it into a fine mist or aerosol. The atomized sample then enters the flame, along with air or oxygen and a fuel gas such as propane or acetylene. The flame provides the thermal excitation necessary to energize the atoms in the sample. As these excited atoms relax, their emitted radiation is detected by a photocell or photomultiplier.
Flame photometry is particularly effective in measuring sodium, potassium, lithium, and calcium elements. The flame used in flame photometry is typically a propane-air flame with a temperature range of 1900-2000 &#176;C, although alternative flames like butane-air or natural gas-air can also be used. Flame photometry has some limitations that can be overcome by using higher temperatures and more reducing flames, such as air-acetylene, along with higher-resolution spectrometric detection. However, these approaches are not cost-competitive compared to the more broadly applicable flame atomic absorption spectrometry or AAS technique.

火焰光度法:概述

Flame photometry, also known as flame emission spectrometry, is a technique used for the qualitative and quantitative analysis of elements present in a ...