Name: experimental methodology for estimation of local heat fluxes and burning rates in steady laminar boundary layer diffusion flames
Uploaded: 2016-06-01T14:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames at JoVE.com

The authors would like to acknowledge financial support for this work from the Minta Martin Foundation at the University of Maryland, College Park.

1.实验计划<ol><li>按照进入火或燃烧研究实验室前的说明和安全防范措施。安全培训，通常需要为新用户。 </li><li>安排您的实验提前进行必要的测试。考虑该实验中，所需的燃料和必要设备的传输的信息。 </li><li>标识感兴趣的液体或固体燃料的实验。因此准备材料。 </li></ol> 2.材料和仪器仪表的研制<ol><li>对于液体燃料的实验，制备多孔不可燃材料（碱土金属硅酸盐棉）的燃料芯。先前的实验4-6已经利用8厘米×8厘米×1.27厘米自由对流测试和10厘米×10厘米×1.27厘米对于强制对流测试厚的片。 <ol><li>通过以从丙烷火炬暴露于扩散火焰烘烤大约20分钟的定的燃料燃烧芯烧灯芯内的有机粘合剂。 </li><li>为了消除来自燃烧芯的侧面的液体燃料的泄漏，从优申请液体硅酸钠与覆盖芯的所有面以外的顶面的注射器。 </li><li>屏蔽所有未用铝箔燃烧芯的顶面。使用高温粘合剂将铝箔粘贴到燃烧芯的侧面。 </li></ol></li><li>固体燃料的试验中，切出的固体燃料的片材。在以前的自由对流实验2中 ，8厘米×8厘米×明确铸聚甲基丙烯酸甲酯（PMMA）为1.27厘米厚的片材已被使用。 </li><li>切出的槽的陶瓷纤维保温板等于燃料样品在其中以后装入样品的大小的片。通常情况下，使用相同的多孔不燃作为燃料燃烧芯;然而，随着高温哑光黑漆密封。 </li><li>检查给定的数据采集硬件和软件。打开软件，并检查脾气执行必需的测试之前ATURE映射算法。 </li></ol> 3.实验装置的制备<ol><li>放置侧视图数码单反相机，使得它与燃料的中心轴对准并且足够远，以使给定的火焰的完整侧视图被捕获。 <ol><li>对于强制对流FL埃姆斯，图像在燃料试样覆盖为16cm×8cm的面积为在热解区计算FL火焰投射距离的中心的视场。 </li></ol></li><li>放置燃料样品上方的横动机构。附加一个50微米的金属丝直径的微热电偶小心横动机构的水平轴。 </li><li>转动可编程步进电机控制器上。 </li><li>在强制流动的实验中，上电风洞的离心式鼓风机的情况。 </li><li>脉冲宽度调制（PWM）控制器设定至7000赫兹，功率设置rangi的频率纳克从16％到对于不同的送风机的速度，用热线风速计验证的50％。 </li><li>与测试继续之前戴安全防护眼镜和耐火手手套。 </li><li>在每次试验中，泡与液体燃料（甲醇或乙醇）到它的点饱和的灯芯。用于8厘米×8厘米×1.27厘米厚灯芯90毫升足以完全浸泡使用二份60ml注射器的燃烧芯，同时为10厘米×10厘米×1.27厘米厚芯120毫升发现是足够的。 </li><li>小心地将燃料浸泡芯/固体燃料板进入燃料芯保持器。检查燃料燃烧芯表面的平坦度与角度计。 </li><li>打开质量平衡软件和检查USB接口的设置。检查质量平衡，并注意在测试前的读数。 </li></ol> 4.在燃烧或火灾实验室运行试验<ol><li>通过完成各组实验后开启排气确保实验设施的正常通风。 Ëxhaust应尽可能最小或在实验过程中分离出来，尽可能帮助消除流动障碍。 </li><li>一个样品被点燃之前，通过采取方格纸或标尺的片材被沿着所述燃料表面的中心轴对齐的图像校准侧视图数码相机。获得从校准图像的平均像素/毫米计数。的图像的后处理过程中使用的像素/毫米此值（在ImageJ的设置测量刻度）。 </li><li>点燃燃料与丙烷火炬，随时触摸它用于液体燃料燃烧芯和均匀地传递火焰的表面上为50〜60秒用固体燃料。 </li><li>均匀点火后立即开始实验时间。用秒表来表示燃烧时间。 </li><li>按下质量平衡软件中的数据采集按钮。 </li><li>监视燃烧芯的质量损失在固定的时间间隔，并将其写入一个测量文件。使用质量平衡软件对于g伊芬目的。 </li><li>在相同条件下重复步骤多个测试4.3-4.6，以确保可重复性。 </li><li>使用质量损失与时间的曲线，以确定稳定燃烧制度，其中，质量损失的线性拟合具有高的R 2值。 </li><li>对于不稳定的固体燃料，从点火50秒为增量烧样品倦怠测量表面的回归（ 如，50秒，100秒，150秒等 ）。 </li><li>切割冷却回归测试后焚烧固体燃料沿中心线。 </li><li>以侧视切固体燃料和负载的照片到ImageJ的。通过将像素用尺子来衡量cm的流向在位置上的回归。一步一步的程序来处理ImageJ的一个给定的图像下面列出。 <ol><li>通过选择文件→打开图像在ImageJ的固体燃料样品的开放式侧视照片。 </li><li>打开校正图像（尺）在ImageJ的固体燃料样品通过选择文件→打开校准图像。 </li><li>叠起的校准图像和固体燃料样本图像。转到图像→堆叠→图像堆栈。 </li><li>设置计量秤:绘制已知距离的两点间的直线，如照片上一个标尺。去分析→设置比例。在设置缩放窗口中的线的长度，以像素为单位，将被显示。键入相应的框中的已知距离和度量单位，然后单击确定。 </li><li>绘制新线，并确认计量秤是正确的。 </li><li>测量两点之间的距离在给定的样品的照片:绘制两个点之间的线。状态栏会显示角度（从水平）和长度。分析→测量（或Ctrl + M或者干脆在键盘上键入M）的值传送到数据窗口。 </li><li>通过测量燃尽样品的厚度和从第i减去它测量在每个流向位置x的回归样品的nitial厚度。 </li></ol></li><li>注意的时间间隔在其上的固体燃料的表面保持大致平坦和用于温度映射，或为了补偿表面回归热电偶位置调整。 </li><li>设置温度映射区间稳定燃烧政权期间捕获测量，固体PMMA约150秒和400秒的液体浸泡过的灯芯。设置基于液体和固体燃料的稳定燃烧时间间隔的温度映射区间。表面附近的推荐的步长为0.25mm 4-6。 </li><li>仔细对准微热电偶用一个XY unislide燃料的表面上。放置在给定的热电偶在样品的宽度的中心。 </li><li>小心移动微热电偶使用XY unislide燃料燃烧芯的前缘。 </li><li>在计算机上运行一个数据采集程序，并从一个文件夹上的D阅读网扫描算法esktop。 注意:一旦实验正在进行，数据收集是自动的，用户只需要监督它，以确保实验正在按计划进行。 </li><li>在计算机上使用数据采集程序，采集数据，并将其写入测量文件。注意，100 4-5 500 6赫兹的采样率在过去的实验中使用。 </li><li>完成后，熄灭火焰。关闭PWM控制器和3相240 VAC电源插座拔下鼓风机的电源插头。 </li><li>关掉步进电机控制器。 </li><li>重复步骤在具有相同的热电偶相似或不同的流动条件附加实验4.12至4.18。 5测试应至少重复每个给定的流量条件（ 例如 ，强制流速或垂直方向）。 </li><li>一个75微米的微热电偶重复步骤4.12 4.18。横越两个热电偶（50微米，金属丝的直径为75μm）沿萨姆在火焰准确辐射校正的区电子路。较小的热电偶也可使用，但破损时常发生了低于50微米的导线。 </li></ol> 5.数据分析<ol><li>阅读从LVM文件到Matlab或其他分析软件处理过的数据。 </li><li>从不同的测试，每个空间点平均温度数据。 </li><li>在每个流向位置计算从平均热电偶数据放射线校正，以下在下面详细描述的科利斯和Williams 10的相关性。 </li><li>通过将辐射校正对原始的温度数据计算补偿温度测量。 </li><li>非维度化温度数据和空间位置。 </li><li>在使用在Matlab或其它专用软件的曲线拟合算法的适当的高阶多项式拟合燃料表面适合无量纲温度数据。表面附近4至6分被发现在以往的研究4-6很好地工作。 </li><li>从高阶多项式拟合到在燃料表面（Y = 0）的非维温度分布的斜率计算在燃料表面上的正常的非维温度梯度。 </li><li>计算从在燃料表面上的相应的本地无量纲温度梯度使用基于雷诺数类比4的理论相关性的局部质量燃烧速率。 </li><li>计算从温度梯度的对流热通量在燃料5-6的表面上。 </li></ol>

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The authors have nothing to disclose.

本研究的目标是开发用于局部质量燃烧率下的各种流场条件液体和固体燃料的估计的新方法。这项研究考虑了两种情况下，自由对流边界层扩散火焰和不同的自由流条件下建立强制对流边界层扩散火焰，同时使用液体和固体燃料。 通过细线热电偶测量了两个液体燃料的灯芯浸泡和过PMMA的固板测量局部灼热率被发现匹配估计等手段，即燃料回归测量。使用基于雷诺数类比12-13，虽然需要稳定，层状燃烧，工作非常好为小规模的样品的相关性，确定所述燃料表面附近这些温度梯度，最终导致数据15％的精度为平均结果和多内多为当地measurem经济需求测试4-6。对于这些局部质量损失率的测量相关的因素取决于代表燃料和其可以计算一个先验的燃料的其他热物理性能的斯波尔丁传质数。结果表明，这种技术可以是提取这些量和理解小型燃料的燃烧在未来更详细地是有用的。 在文献中的其他研究已经在这里扩大了代表工作纳入对垂直方向的样品数值模拟4和实验，燃烧自如4,5和环境下风6水平安装的样品。对于这些配置中，热通量的分量也被局部地采用相同的细金属线热电偶技术非常靠近冷凝燃料表面确定在燃料表面上。而热通量的分量已在过去被测量通过使用嵌入式计，THI小号的技术是微创并提供对流热通量，这还不可能之前的直接测量。 应特别注意在实验过程中选择特定的配置和装置的设置时作出。在这些实验中，热电偶选择用于步骤3.2从一个小的陶瓷管伸出，保持在电线上的张力，使热电偶的位置相对固定。使用悬浮在整个火焰无管的热电偶丝将减少从陶瓷管可能的干扰，但它将使定位热电偶的具体位置更变量作为导线趋于随温度扩大。有时在配置改变可以诱导在样品的宽度的影响（例如倾斜样品）。如果安装是从那些在过去的4-6个研究修改，围绕一步4.14偶尔会检查火焰温度MEA在样品的宽度surements显示没有显著变化应采取（ 即 ，2维假设仍持有）。否则，一个三维测绘系统将需要实施。 在执行实验中最重要的步骤有准备的燃料和正确使用热电偶要做。在热电偶的定位即使是轻微的偏差可能会造成误差，因此必须小心定位步骤3.2，4.13和4.14热电偶时服用。燃料燃烧芯也必须放置成使得平的表面尽可能保持（步骤2.1）和所有的填充材料应烘烤灯芯（步骤2.1.1）的。 排气系统，在步骤4.1激活也应保持最小或孤立尽可能接近的实验，以帮助消除流动障碍。这应该确保小阳线不是吹的地方测试将发生（无风）进行检查。挡板，屏幕在一大的空间的单独封闭设施或测试可以被用来实现此目的。在步骤4.2中，固体燃料必须尽可能均匀地点燃越​​好。而丙烷炬是不这样做的最理想的来源，实验没有发现以在过去的工作4-6点火源敏感。敏感性点火源应该在通过改变时间或曝光的强度和观察的稳定质量燃烧速率的实验结果记录在案。如果观察到的灵敏度辐射板应交替使用点燃样品。固体燃料，或通过质量损失率作为观察应该有一个短区域期间拍摄的温度映射不具有大的（&gt; 300秒）稳定燃烧区域的任何燃料。例如，在步骤4.13的映射被推荐用于PMMA被接管的第150秒，而燃料仍然相对平坦和表面回归得到了很好的证明。面回归测量可以用ImageJ或其它类似图像处理软件来测量照片的像素，并转换为长度。可替代地，一个数字千分尺可以被用于测量固体板的表面回归其冷却后（注意的"鼓泡"的材料，如聚甲基丙烯酸甲酯的表面必须打磨第一）。 所提出的燃烧率的相关性是基于层的假设，但是，它是假设，此技术应遵循的燃料表面的紊流燃烧类似的形式，尽管它必须通过实验确定一个修改功能关系。这里提出的工作可随后扩展到湍流边界层燃烧和驱动入射光热通量到燃料表面可以进一步调查湍流和气相放热之间关联的相互作用。 该理论在其燃烧速度相关的基础也忽略了辐射。该理论过于简单化乐ading在其预测能力的不确定性，未涵盖目前的工作情况。例如，给定的方法可能不适合高烟熏火焰工作，其中的热通量的表面主要是辐射。对于大的紊流壁的火焰，在那里的辐射热通量的冷凝燃料表面是高，建议燃烧率的相关性可能会或可能不会起作用。在所提出的相关辐射效应列入是，因此，可取的和进一步的研究，必须以确定这个函数关系进行。本领域需要在模型改进如果确信预测方法可用于这样的火焰来实现。

而关键的进步已经在消防安全研究领域在过去一个世纪已经取得，预计火焰蔓延率仍然为许多材料在不同配置的挑战。火焰蔓延经常进行无论是在建或自然环境一系列新元素的点火，从点火的初始源发射。的个别燃烧材料的燃烧特性的知识是为了预测火焰蔓延的这些速率关键的，因为这有助于以未点燃的元件加热的速率。因此燃料元件的热释放速率（HRR）已被列为在火灾研究1最基本的量，约等于在凝相燃料的燃烧（质量损失）率，即的蒸发速度固体燃料的液体燃料或热解率。 燃烧速度可以被认为是一个母校的可燃性的量度IAL并在火灾危险性分析的关键参数和灭火系统的设计。本地质量损失（或燃烧）率，M"F，A垂直壁的是，特别是，在许多火有关的问题，例如在墙壁上的火焰传播，火灾增长，能量释放率中的一个重要的变量外壳火，烟和热气体羽流的传播有关的垂直壁向上火焰蔓延的预测，火焰高度必须计算，这取决于总的能量释放速率;即，反过来，是直接由影响集成翻墙2-3的整个热解地区的当地质量损失率。虽然这些集成的质量损失率方面的知识都比较熟知，在沿燃面增量位置质量燃烧率的认识不为人所熟知因为实验技术测量这些速率极为有限。提供这种"局部"质量燃烧率的技术信息可以以冷凝燃料的燃烧提供增加的洞察力，使研究人员能够进一步理解其区别不同的燃料或彼此配置的机制。因为大多数材料在小规模的第一评估（ 例如，在一锥形量热仪1），逻辑第一步是提供一个技术以测量在小型，层流扩散火焰以上稠燃料表面局部质量燃烧速率。 这里介绍的工作，讨论了关于建立了浓缩燃料表面稳态层火焰进行实验，实验方法和协议。采用微型热电偶局部温度梯度的估计是当地的质量燃烧率和热通量在这些火焰4-6估计的特别有用的技术。文献数据的分析显示了在凝析确定局部传热，燃烧和摩擦系数的困难SED燃料表面，这对于理解物理和驱动一个特定的火，它的传播4-6的底层机制很重要。热流，这仍然可能超过燃料表面局部地区最完善的测量火属性，成分已被证明难以估量。效果，例如燃料的变异性，热通量的可扩展性，实现了稳定状态条件和不同的热通量量规技术的困难已经对数据的一个相当宽的散射这是在文献4可用作出了贡献。局部温度梯度以高精度的测量将有助于缓解这种变化，并且还提供了可用于层状壁火灾，一个典型的火研究问题的数值验证传热关系。这样的实验也在探索在层流和湍流边界层可燃浓缩燃料表面和气相火焰之间的动态关系有用秒。方法以精确和可重复的方式准确地捕捉这些温度梯度在下面描述。

<table><tbody><tr><td colspan="4">&lt;strong&gt;Thermocouples with connectors and clamps&lt;/strong&gt;</td></tr><tr><td>Unsheathed Fine Gauge T/C</td><td>P13R-002</td><td>Omega Engineering, Inc.</td><td>Fine wire microthermocouples (R-type)</td></tr><tr><td>Unsheathed Fine Gauge T/C</td><td>P13R-003</td><td>Omega Engineering, Inc.</td><td>Fine wire microthermocouples (R-type)</td></tr><tr><td>Ceramic 2 hole round - 5 pk</td><td>TRX-010364-6</td><td>Omega Engineering, Inc.</td><td>Ceramic tubes to hold the fine wire thermocouples</td></tr><tr><td>Thermocouple extension wire</td><td>EXTT-RS-24-100</td><td>Omega Engineering, Inc.</td><td>Thermocouple extension wire</td></tr><tr><td>Male Female Connectors</td><td>SHX-R/S-MF</td><td>Omega Engineering, Inc.</td><td>Connectors for R-type thermocouples&amp;nbsp;</td></tr><tr><td>Accessories</td><td>MSRT-116-10</td><td>Omega Engineering, Inc.</td><td>Rubber tubes for maintaining grip for the ceramic tubes at the connectors&#039;s end</td></tr><tr><td colspan="4">&lt;strong&gt;Traverse mechanism&lt;/strong&gt;</td></tr><tr><td>X slide, travel = 10 inch, 0.025 in/rev, limits, NEMA 17</td><td>XN10-0100-E25-71</td><td>Velmex Inc.</td><td>Velmex unislide</td></tr><tr><td>Vexta type 17, 1.8 deg/step 2phase, single shaft stepper motor</td><td>PK245-01AA</td><td>Velmex Inc.</td><td>Stepper motor&amp;nbsp;</td></tr><tr><td>Mounting cleat, standard using 6-32 bolts</td><td>XMC-2</td><td>Velmex Inc.</td><td>Mounting accessories for the given Velmex unislide</td></tr><tr><td>6-32 x 7/16 SH Cap Screw for Xslide in X &amp;amp; Y axis</td><td>XMB-1</td><td>Velmex Inc.</td><td>Mounting accessories for the given Velmex unislide</td></tr><tr><td>X slide, travel = 10 inch, 0.025 in/rev, limits, NEMA 17</td><td>XN10-0100-E25-71</td><td>Velmex Inc.</td><td>Velmex unislide</td></tr><tr><td>Vexta type 17, 1.8 deg/step 2phase, single shaft stepper motor</td><td>PK245-01AA</td><td>Velmex Inc.</td><td>Stepper motor&amp;nbsp;</td></tr><tr><td>Mounting cleat, standard using 6-32 bolts</td><td>XMC-2</td><td>Velmex Inc.</td><td>Mounting accessories for the given Velmex unislide</td></tr><tr><td>6-32 x 7/16 SH Cap Screw for Xslide in X &amp;amp; Y axis</td><td>XMB-1</td><td>Velmex Inc.</td><td>Mounting accessories for the given Velmex unislide</td></tr><tr><td>Control, 2 Axis programmable stepping motor control, 1 motor at a time</td><td>VXM-2</td><td>Velmex Inc.</td><td>Stepper motor controller</td></tr><tr><td>USB to RS232 DB9 Serial Communication cable 10 ft</td><td>RPC-USB-RS232-3M</td><td>Velmex Inc.</td><td>Serial communication cable between the stepper motor controller and&amp;nbsp; computer</td></tr><tr><td colspan="4">&lt;strong&gt;Data acquisition hardware&lt;/strong&gt;</td></tr><tr><td>NI 9214 16-Ch Isothermal TC, 24-bit C Series Module for high accuracy thermocouple measurements (includes terminal block)</td><td>781510-01</td><td>National Instruments</td><td>Thermocouple data acquistion card</td></tr><tr><td>Power Cord, AC, U.S., 120 VAC, 2.3 meters</td><td>763000-01</td><td>National Instruments</td><td>Power cord for the 8 slot C-DAQ chassis</td></tr><tr><td>cDAQ-9178, CompactDAQ chassis (8 slot USB)</td><td>781156-01</td><td>National Instruments</td><td>C-DAQ chassis for NI 9214 and NI 9239</td></tr><tr><td>EMI Suppression Ferrite for NI 9229/39 BNC</td><td>782801-01</td><td>National Instruments</td><td>Accessories for NI 9239 data acquistion card</td></tr><tr><td>NI 9239 BNC, 4-Ch +/-10&amp;nbsp;V, 50&amp;nbsp;kS&amp;#8288;/&amp;#8288;s per channel</td><td>780181-01</td><td>National Instruments</td><td>Data acquistion card for hot wire anemometer system</td></tr><tr><td>cDAQ-9171, CompactDAQ chassis (1 slot USB)</td><td>781425-01</td><td>National Instruments</td><td>C-DAQ chassis for NI 9214&amp;nbsp;</td></tr><tr><td colspan="4">&lt;strong&gt;Cameras&lt;/strong&gt;</td></tr><tr><td>Nikon D7100 24.1 MP DX-Format CMOS Digital SLR with 18-105&amp;nbsp;mm f/3.5-5.6 AF-S DX VR ED Nikkor Lens</td><td>Nikon D7100</td><td>Amazon</td><td>Digital SLR camera for taking top-view flame photographs</td></tr><tr><td>Canon EOS Rebel T5 DSLR CMOS Digital SLR Camera and DIGIC Imaging with EF-S 18-55&amp;nbsp;mm f/3.5-5.6 IS Lens</td><td>Canon EOS Rebel T5 DSLR&amp;nbsp;</td><td>Amazon</td><td>Digital SLR camera for taking side-view flame photographs</td></tr><tr><td colspan="4">&lt;strong&gt;Mass balance&lt;/strong&gt;</td></tr><tr><td>Mettler-Toledo, MS32001L Balance Prec 32,200&amp;nbsp;g x 0.1&amp;nbsp;g</td><td>97035-654</td><td>VWR</td><td>Precision electronic mass balance for measuring average mass burning rate</td></tr><tr><td colspan="4">&lt;strong&gt;Mini CTA system&lt;/strong&gt;</td></tr><tr><td>MiniCTA Anemometer Package for wire- and film-probes</td><td>9054T0461</td><td>Dantec Dynamics</td><td>Hot wire system for measuring velocities and turbulence intesity at the wind tunnel outlet</td></tr><tr><td colspan="4">&lt;strong&gt;Wind tunnel equipment&lt;/strong&gt;</td></tr><tr><td>1/2 in. x 4 ft. x 8 ft. C-3 Whole Piece Birch Domestic Plywood</td><td>Model # 833185</td><td>Home Depot</td><td>Used to make the laboratory scale wind tunnel</td></tr><tr><td>Woodgrain Millwork WM 206 11/16 in. x 11/16 in. x 96 in. Wood Pine Corner Moulding</td><td>Model # 109610</td><td>Home Depot</td><td>Used to make the laboratory scale wind tunnel</td></tr><tr><td>Extension Spring, Loop Ends, 6.562&quot; Overall Length, Pack of 6</td><td>1330K26</td><td>McMaster-Carr</td><td>Used to make the laboratory scale wind tunnel</td></tr><tr><td>Strainer Grade Wire Cloth, 30x30 Mesh, 0.0130&quot; wire diameter. 12&quot;x12&quot; sheet</td><td>9241T41</td><td>McMaster-Carr</td><td>Used to make the laboratory scale wind tunnel</td></tr><tr><td>Strainer Grade Wire Cloth, 40x40 Mesh, 0.0065&quot; wire diameter. 12&quot;x12&quot; sheet</td><td>9241T42</td><td>McMaster-Carr</td><td>Used to make the laboratory scale wind tunnel</td></tr><tr><td>Mobile Lift Table Foot-Operated, 600# Capacity, 10&quot; - 33&quot; Table Height</td><td>2791T22</td><td>McMaster-Carr</td><td>Table to hold the experimental setup</td></tr><tr><td>ebm-papst p/n: G3G250-MW75-05 (EC Centrifugal blower, 200-240&amp;nbsp;V, 3-phase, 50/60&amp;nbsp;Hz, M3G112-EA motor, 2.2&amp;nbsp;kW)</td><td>G3G250-MW75-05</td><td>Ebm papst</td><td>Blower for the wind tunnel</td></tr><tr><td>ebm-papst p/n: HX0C-003-000-04 (Controller)</td><td>HX0C-003-000-04</td><td>Ebm papst</td><td>Pulse width modulation controller for controlling the speed of the blower</td></tr><tr><td>8020 1&amp;rdquo; X 1&amp;rdquo; T-SLOTTED PROFILE&amp;nbsp;</td><td>8020-1010</td><td>80/20 (Rankin Automation)</td><td>Used to create a framework for the wind tunnel</td></tr><tr><td>Momentive/GE Silicone Sealant RTV108, 10.1-oz Cartridge, Semi-Clear</td><td>7545A472</td><td>McMaster Carr</td><td>Sealant for the wood</td></tr><tr><td colspan="4">&lt;strong&gt;Software&lt;/strong&gt;</td></tr><tr><td>LabVIEW</td><td>Contact vendor</td><td>National Instruments</td><td>Used for continuous temperature data acquistion and analysis. Alternatively used for positioning the thermocouple.</td></tr><tr><td>Mettler Toledo mass balance software</td><td>Contact vendor</td><td>Mettler Toledo</td><td>Used for measuring the mass loss rate of the condensed fuel wick / solid plate with time</td></tr><tr><td>ImageJ</td><td>Free download</td><td>NIH, http://imagej.nih.gov/ij/</td><td>Used for measuring the flame standoff distance and surface regression of the solid fuel plate</td></tr><tr><td>Matlab</td><td>Contact vendor</td><td>Mathworks</td><td>Used for post-processing of data</td></tr><tr><td>Fortran 90/95</td><td>Contact vendor</td><td>The Fortran company</td><td>Used for post-processing of data</td></tr><tr><td colspan="4">&lt;strong&gt;Materials&lt;/strong&gt;</td></tr><tr><td>Methanol&amp;nbsp;</td><td>UMD Chem Store</td><td>NA</td><td>Liquid fuel</td></tr><tr><td>Ethanol&amp;nbsp;</td><td>UMD Chem Store</td><td>NA</td><td>Liquid fuel</td></tr><tr><td>safety glasses</td><td>UMD Chem Store</td><td>NA</td><td>Used for safety purpose</td></tr><tr><td>spray bottle</td><td>UMD Chem Store</td><td>NA</td><td>Used for carrying water in case of emergency</td></tr><tr><td>Syringe 60 cc</td><td>UMD Chem Store</td><td>NA</td><td>Used for soaking the liquid fuel wick with liquid fuels</td></tr><tr><td>Optically Clear Cast Acrylic Sheet, 1/8&quot; Thick, 24&quot; x 48&quot;</td><td>Mc master carr</td><td>8560K262</td><td>Solid fuel PMMA</td></tr><tr><td>Loctite Proxy Pak (Hi-temp adhesive)</td><td>Mc master carr</td><td>7556A33</td><td>Used for covering the sides of the wick with aluminum foil</td></tr><tr><td>Hi-Temp Aerosol Spray Paint (Black)</td><td>Mc master carr</td><td>7832T1</td><td>Used for painting the insulation&amp;nbsp;</td></tr><tr><td>Self-Igniting Economy Propane Gas Torch Adjustable Flame, 4,179&amp;nbsp;Btu/hr</td><td>Mc master carr</td><td>78245A3</td><td>Propane torch for igniting the solid fuel plate</td></tr><tr><td>Heat-Resistant Cotton Glove W/Nitrile Coating, 400 Deg F Max Temp, 10&quot; Lg, Large</td><td>Mc master carr</td><td>56025T1</td><td>Used for safety purpose</td></tr><tr><td>Modular Protective Screen with Tie-on Curtain, 6&#039;&amp;nbsp;Height x 4&#039;&amp;nbsp;Width Abrasion-Resistant Fiberglass</td><td>Mc master carr</td><td>9145T84</td><td>Fire-resistant curtain for the background</td></tr><tr><td>Multipurpose Aluminium Alloy 6061 .125&quot; thick, 12&quot; x 24&quot;</td><td>Mc master carr</td><td>89015K28</td><td>Used for holding the insulation</td></tr><tr><td>Marine grade plywood 1/2&quot; thick, 12&quot; x 24&quot;</td><td>Mc master carr</td><td>1125T32</td><td>Used for holding the experimental setup</td></tr><tr><td>Multipurpose Aluminium Alloy 6061 U-channel, 2&quot; base x 1-1/4&quot; legs, 1&#039; length</td><td>Mc master carr</td><td>1630T473</td><td>Used for holding the aluminum plate, insulation and wick</td></tr><tr><td>Architectural Anodized Aluminium (Alloy 6063) 90 deg angle, 1/8&quot; Thk, 1/2&quot; x 1/2&quot; legs, 6&#039; L</td><td>Mc master carr</td><td>4630T21</td><td>Used for holding the aluminum plate, insulation and wick</td></tr><tr><td>Aluminium Inch T-Slotted Framing System Concealed 90 degree connector, for 1&quot; extrusion</td><td>Mc master carr</td><td>47065T155</td><td>Used for holding the aluminum plate, insulation and wick</td></tr><tr><td>Aluminium Inch T-Slotted Framing System Extended 90 degree bracket, Single, 4 Hole, for 1&quot; extrusion</td><td>Mc master carr</td><td>47065T175</td><td>Used for holding the aluminum plate, insulation and wick</td></tr><tr><td>Aluminium Inch T-Slotted Framing System Four-Slot single, 1&quot; solid extrusion, 4&#039; length</td><td>Mc master carr</td><td>47065T101</td><td>Used for holding the aluminum plate, insulation and wick</td></tr><tr><td>1/2&quot; x 48&quot; x 36&quot; (Superwool 607 insulation board) 1 carton containing 12 sheets</td><td>Mccormick Insulation</td><td>Superwool 607&amp;nbsp;</td><td>Insulation material for making the wick and the wick holder</td></tr></tbody></table>

experimental methodology for estimation of local heat fluxes and burning rates in steady laminar boundary layer diffusion flames

建模凝相燃料的现实燃烧行为仍然够不着，部分原因是因为一个未能解决在气相火焰和凝相燃料之间的界面发生的复杂的相互作用。目前的研究提供了一种技术，探索在层流边界层可燃浓缩燃料表面和气相火焰之间的动态关系。实验先前已在以上固体和液体燃料两者被迫和自由对流的环境下进行。一个独特的方法的基础上，雷诺相似，被用来估计当地质量燃烧率和火焰的热通量为利用当地温度梯度的燃料，这些表面层流边界层扩散火焰。当地质量燃烧速率和从火焰的对流和辐射热反馈通过使用壁邻近映射的温度梯度通过两轴TRAVER同时在热解和羽流区域测量被SE系统。这些实验是费时并且可以挑战以设计为冷凝的燃料表面稳定燃烧为以下点火的时间只有一个有限的时间。燃料表面附近的温度分布需要被稠燃料表面的稳定燃烧过程中以非常高的空间分辨率，以捕捉局部温度梯度的合理估计映射。从热电偶辐射热损失仔细校正也可用于精确测量是至关重要的。由于这些原因，在整个实验装置需要用计算机控制的横移机构是自动化的，从而消除大多数错误由于微热电偶的定位。步骤大纲可重复地捕捉近壁的温度梯度，并用它们来评估当地的燃烧速度和热通量提供。

实验已经在垂直配置和在马里兰大学一个独特的水平风洞设施，在图1中所示被执行两者。而不是一个传统上拉或闭合返回风洞，在马里兰大学风洞设施使用可变速度鼓风机进行加压的100×75×100厘米增压驱动空气在相对端流出的管道。该配置使得能够连续燃烧实验烟雾不重新循环，风洞不被损坏或火灾的影响，热电偶能够在整个采样部分自由移动。出口管包括连接到一个通风122厘米30.5厘米宽的会聚区的。拉直的流动，并减少进入的湍流强度，细筛网放置在会聚部分的入口和出口和一个5厘米厚的蜂窝与0.3厘米孔是放在上游110厘米从隧道出口。离开风洞的流的速度是通过改变用脉冲宽度调制所述风扇的速度的控制（PWM）控制器和燃料样品被放置在隧道，其中，流速已经通过使用检查的出口的热线风速计。 在风洞的出口燃料样品放置在其上连续地测量样品随时间的质量损失的测压元件的顶部。以避免风的负载传感器的扰动，将样品升高上的铝薄片（30.5×61.0厘米×1.5mm厚）由两个U形支架和1.27厘米厚的陶瓷纤维保温板包围，以确保光滑的表面周围的燃烧样本。电路板的顶部表面用与发射率约为98％的高温度黑色无光漆以确保良好的背景为肉眼观察火焰，以密封绝缘其中还包含有机粘合剂。因为绝缘板呈现出较钝体的进入流，直接在风洞的出口将样品设置导致流动分离和火焰观察显著湍流。由哈等人先前的工作中发现，一个延伸板附连到燃料样品的前端部防止该流动分离和确保传入到样品层流剖面。因此一个10厘米宽40.6厘米长的薄，金属唇是从样品到风洞出口的前沿安装，提供了最终被发现匹配现有的理论7层流扩散火焰。 在测试液体燃料需要多孔不燃灯芯。一个10厘米×10厘米×1.27厘米厚片碱土硅酸盐羊毛强迫流动实验被选择，由于其高孔隙率和低的导热性。在邻即刻申请，以防止从样品燃料的泄漏，硅酸钠胶水用于铝箔应用于所有除正面。该样品也中"烘烤"通过使喷灯在样品约20分钟，在该点的火焰从黄色变为蓝色（表示从样品中除去粘合剂的）。在测试过程中，以除去有机粘合剂，灯芯浸泡用约120毫升这被认为是饱和的为宽10厘米芯吸点液体燃料（乙醇或甲醇）的。 的燃料的质量燃烧速率通过测量燃烧过程中从样品随时间失去质量以1Hz的速率来确定。样品设置用用32.2公斤的最大容量，并为0.1g的分辨率，足以精细测量高精度这种质量损失率精度质量平衡的支持。通过一个喷灯以下样品的点火，共同的质量损失率ndensed燃料增加作为时间的函数，最终达到恒定的速率并最终朝着测试结束变淡作为燃料烧坏。这个"稳"区域，其中燃料的蒸发，而不是扩散通过灯芯占主导地位燃烧，是进行数据采样的感兴趣区域。用于液体灯芯，发现样品具有稳定质量损失率燃烧约400秒，约一测试的中间的80％。呈现所有燃烧率是在特定条件下至少六个反复试验，其中，测量的重现性被发现是平均值的1.2％之内的平均值。 用于固体燃料样品的测试，聚甲基丙烯酸甲酯（PMMA）作为它燃烧相对稳定，并且不烧焦。为了点燃样品，喷灯通过了在样品表面为50-60秒，在该点的整个表面均匀地点燃。由于燃料样品小，结果为非常可重复的实验结果，该方法被认为是足够的点火。不同于浸入不燃芯的液体燃料，固体燃料倒退作为时间的函数，并因此从未真正地实现稳定的制度。相反，被选燃烧早期被采样，其中燃料保持相对平坦，通过实验确定第一150秒以下点火期间发生。 对于液体和固体燃料，温度超过燃料表面在使用细金属丝热电偶气相被映射。对于聚甲基丙烯酸甲酯，温度在6个点为0.25毫米的间隔（对于强制对流测试）从熔融层到气相起始表面上方进行取样。对于液体燃料，这些测量从燃料的薄层的表面在相同的分辨率进行到6分。这些配置都在12个地点取人翁燃料表面的长度，液体样品400秒点火的内和150秒为聚甲基丙烯酸甲酯中。 上述温度测量进行了使用R型的Pt /铂13％铑微热电偶（点焊）具有两个导线的直径，50微米（0.002英寸）和75微米（0.003英寸）具有大约100微米的小珠的直径和为150μm，分别。热电偶的大小被选择使得所述热电偶是尽可能小而不重复破损（以最小化所需的辐射校正），但是一些辐射校正仍然必需的。使用不同直径的两个热电偶分别以更好地确定合​​适的辐射校正（稍后描述）选择的。然后微热电偶使用一组计算机控制的XY unislides的为1.5微米的最大空间分辨率遍历。然后电压信号分别进行了ACQuired，空调，并通过数据采集模块，频率最高可达0.02°C的测量灵敏度数字化。 LabVIEW软件被用于同步两个50微米和75微米的与温度测量在样品电线直径热电偶运动。 为了确定相对准确的辐射校正，描述的两个热电偶尺寸在反复试验遍历在同一位置。科利斯和威廉姆斯的相关性，适用于从样品5-6,8热损失， <img alt="式（1）" src="/files/ftp_upload/54029/54029eq1.jpg" /> （1） 其中，Nu为努塞尔数与再= 的Ud w / v 的是雷诺数，这是为0.02 &lt;重新&lt;44获得与性能评价在该膜的温度，Τ 男 ，平均气，Τ 克 ，和热电偶，ΤTC温度。在此，作为本地气体流速U和运动粘度V所示的雷诺数Re被定义。ðw的方程。 （1）表示的热电偶丝直径。 用于稳态测量，如在这里描述的情况下，在热电偶结能量平衡减少了对流辐射热平衡由下式给出（忽略误差由于传导和催化效果）， <img alt="公式（2）" src="/files/ftp_upload/54029/54029eq2.jpg" /> （2） <img alt="公式3" src="/files/ftp_upload/54029/54029eq3.jpg" />60;（3） 其中，Τg是实际气体温度，Τtc是热电偶结（或珠）温，ΤSURR是周围环境的温度，εtc是热电偶结的发射率，σ是Stefan-Boltzmann常数，h是流过定义为h = K女/ 旦 。k处的热电偶结的对流热传递系数是气体的热导率，Nu为努塞尔数，而d是热电偶丝直径。努塞尔数相关的选择是非常重要的，因为，如式所示计算辐射校正所测量的热电偶的温度。 （3），所述辐射校正是成反比的努塞尔数。这种选择是复杂的，但是，由于EXI<html>多个"适当"的努塞尔数的相关性的stence和在气体混合物的周围的热电偶，特别是其热导率的特性估算的难度。在文献证据本体，然而，清楚地表明，一圆柱形努塞尔数的相关性是最适当用于说明几乎所有实际的热电偶5-6，优选该科利斯和Williams 8的对流热传递。 努塞尔数的相关性，必须代入稳态对流辐射平衡（等式3）和忽略温度依赖性小，两个方程具有两个未知数（即Τg且U）的一个系统被形成， <img alt="公式4" src="/files/ftp_upload/54029/54029eq4.jpg" /> （4） T"FO:保together.within页="1"&gt;和<img alt="公式5" src="/files/ftp_upload/54029/54029eq5.jpg" /> （5） 方程（4）和（5）必须在每个点处迭代地一起解决，因为气相电导率和运动粘度都是温度的函数。胎圈温度应作为气体温度的第一次迭代，直到低错误被接近，以评估热导率和运动粘度，与迭代值重新拍摄。当求解方程，看来该辐射校正（ 即热电偶读数和实际温度之间的差）增大为较大直径的热电偶，并且与在胎圈增加流速减小。ð 瓦特 1以及d W 2在方程。 （4）和（5）代表怨恨在我​​们的研究中使用的热电偶丝直径。 珠（εTC）的发射也可以找到与使用雅各布·9概括的方法的温度的功能。在他的分析，雅各布解决麦克斯韦波动方程折射在金属表面的电阻率的功能复杂的指数。一个假设是采取低电阻率和折射的大型指标的限制，这对于拥有真正的金属，产生对铂金的总半球发射率（PT）作为一个简单的相关性， <img alt="公式6" src="/files/ftp_upload/54029/54029eq6.jpg" /> （6） 在那里，铂金，Rê≈ - [R E，273 T / 273，以T为K和R e，273 &lt;EM&gt; = 11x10 -6Ω-厘米。 因此，铂发射率变为5-6 <img alt="公式7" src="/files/ftp_upload/54029/54029eq7.jpg" /> （7） 0 &lt;T &lt;2,330 K.热电偶珠或结的辐射，如出现在方程。 （4）和（5）因此，可以通过使用上述表达式进行评估。迭代是没有必要的方程（6）和（7）因为胎圈温度的实际值是已知的，仅该气体的温度和速度在方程。 （4）和（5）需要迭代求解。 在实验过程中，两个热电偶被准确运行到相同的测量点和数据进行取样以考虑在温度测量中辐射校正。该应用改正，结果Ø˚F迭代方程。 （4）和（5）分别为小，例如仅+79 K中1700 K时为50μm丝直径的热电偶和小于5 K.燃料表面6附近。由于热电偶也高温的交叉区域梯度考虑通过导线传导损耗也必须考虑，但由于热电偶导线的小的横截面面积，计算这些误差为&lt;1％，因此，没有修正是必要的5-6。 与位于在风洞出口处的气流的中心的燃料表面，被用于微热电偶和热丝风速计测量提供容易进入燃料表面。在风洞（没有燃烧）的自由流速度的冷流道，风洞的ü∞使用的在50,000样本/秒的速率采样，总所需时间一热线风速计被校准每点10秒的n个。沿着整个隧道出口处的速度分布拍摄，揭示了一个一致的塞流从隧道出口的中心发出。这是预期要平方信道，例如我们的风洞的出口。通过斯福尔扎等人 10以前的测量表明，2.6和8.8之间的正方形射流雷诺数Re D的潜在核心长度×10 4个应该是大约5 天的出口，其中d是该通道的高度的下游。为D =30.48厘米，风洞出口的宽度，重新d为1.5和3.9的含义之间×10 4×10 4个样品保持在隧道出口的1 天 （20厘米）内。这些测量的可重复性是平均值的3％以内。 温度分别为10厘米的点燃的片的表面上测得×10厘米×1.27厘米PMMA放置在风洞中的Ù∞R = 0.79米/秒和2.06米/秒操作所述出口。以上概述的过程被用来捕捉温度测量其均在正常长度Y * = Y / L和温度T * =方面无量纲（T - T的W，P / T FL，广告 - T的W，P）其中ΤW，p和ΤFL，广告代表壁和绝热火焰温度，分别对于给定的燃料，y，其中，温度测量垂直于燃料表面的位置和L燃料表面的长度。无量纲温度梯度垂直于表面，然后计算，（∂T * /∂Y *）Y * = 0由五阶多项式拟合无量纲的温度和在燃料表面，Y中提取的斜率* = 0。 图2（a）示出了沿着燃料表面的长度，这些无量纲温度梯度。它们显然最高在燃料表面，其中该火焰是最接近燃料表面的前缘，并且朝向后缘（X = 100毫米），其中，所述火焰是从燃料表面最远降低。无量纲的温度梯度可以用于通过应用相关4,6确定本地质量燃烧速度， <img alt="式（8）" src="/files/ftp_upload/54029/54029eq8.jpg" /> （8） 其中B是给定的燃料的质量传递数中，k 瓦特在壁温度评价空气的热导率， 中 c p在燃料的绝热火焰温度评估的空气的比热，且L &lt;/ em&gt;的热解燃料表面的长度。则本地质量燃烧速率被发现以类似于无量纲的温度梯度的方式来改变， 如图2（b）所示。 不像液体燃料，对于聚甲基丙烯酸甲酯的局部质量燃烧速率也可通过在一定时间2,11固定间隔测量局部表面回归近似后验。 PMMA样品代表的条件下烧成开始在50秒的时间段，并在50秒的间隔后样​​品的消光增加。对于聚甲基丙烯酸甲酯热解质量流量在每个x位置计算沿着中心对称轴使用由皮佐等人 11给出一阶近似，在文献中其它地方4-6讨论。聚甲基丙烯酸甲酯的平均密度，ρS =1190公斤/ m 3的用沿燃料表面测得的表面回归到一起使用沿着燃料样品的长度每50秒时间间隔内到达的质量损失率。尽管较短的时间的步骤将是所希望的，在测量误差使当时间的步骤是小于50秒5它变得不切实际。 从与那些从回归型材热电偶比较本地质量损失速率，从100和150秒的燃料烧尽时间数据被用来比较在图2所示的本地质量燃烧速率（b）中 。这些时间对应于采取了这些测量大致相同的时间。如在图中可以看出，测量局部质量燃烧速率的两种方法显得非常靠近彼此，这表明该方法对于这些类型的火焰的效果很好。 对于对流主导火焰如这些小，层的人，在燃料表面温度梯度也可以用来提取CON的对流热通量，因为它们是在本质上，直接关系到在表面上的温度梯度。使用测量的​​质量损失率，火焰热通量的组件也可以沿着热解区萃取。使用几个近似在燃料表面上的热平衡，在别处文献2-3中列出，这些组件可PMMA的燃烧板的表面上确定。 图3示出了这样的结果，对于聚甲基丙烯酸甲酯火焰与周围自由稳定û∞=2.06米/秒的速度-stream。因此，该技术可以是在评估了若干措施来描述燃料小样本的燃烧，从而增加了燃烧过程，特别是在固体和气体相之间的关系的理解是非常有用的。 <img alt="图1" src="/files/ftp_upload/54029/54029fig1.jpg" /> 图1. 实验人设置（ 一 ）使用过强制对流边界层扩散火焰来衡量质量损失率和温度分布的实验装置示意图。 （ 二 ）调查强制流动下边界层扩散火焰的实验装置。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54029/54029fig1highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/54029/54029fig2.jpg" /> 图2. 温度梯度和局部灼热率结果。（a） 中的燃料表面正常的无量纲温度梯度在û∞R = 0.79米/秒分别和2.06米/秒，聚甲基丙烯酸甲酯边界层扩散火焰的变化。 （ 二 ）PMMA边界层diffusi局部肿块燃烧率的变化在不同自由流条件下的火焰。通过无量纲温度梯度得到当地群众的燃烧率是针对通过PMMA表面的回归获得的实验数据进行了比较。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54029/54029fig2highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/54029/54029fig3.jpg" /> 图3. 热通量的在U A PMMA边界层扩散火焰的热解区火焰热通量的各种组件的强制流动，分布的结果 ∞=2.06米/秒。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54029/54029fig3highres.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames at JoVE.com

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

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 ...

experimental-methodology-for-estimation-local-heat-fluxes-burning

Universidad San Sebastian

Research

JoVE Journal

Engineering

11.7K 次观看.  University of Maryland. 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. 

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

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

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

烧蚀材料在试验过程中等离子体发生器发射光谱边界层研究

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

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 ...

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

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This flexible tool offers a detailed observation of chemical gas-phase kinetics in reacting flows under well-controlled conditions. The vast range of operating conditions available in a laminar flow reactor enables access to extraordinary combustion applications that are typically not achievable by flame experiments. These include rich conditions at high temperatures relevant for gasification processes, the peroxy chemistry governing the low temperature oxidation regime or investigations of complex technical fuels. The presented setup allows measurements of quantitative speciation data for reaction model validation of combustion, gasification and pyrolysis processes, while enabling a systematic general understanding of the reaction chemistry. Validation of kinetic reaction models is generally performed by investigating combustion processes of pure compounds. The flow reactor has been enhanced to be suitable for technical fuels (e.g. multi-component mixtures like Jet A-1) to allow for phenomenological analysis of occurring combustion intermediates like soot precursors or pollutants. The controlled and comparable boundary conditions provided by the experimental design allow for predictions of pollutant formation tendencies. Cold reactants are fed premixed into the reactor that are highly diluted (in around 99 vol% in Ar) in order to suppress self-sustaining combustion reactions. The laminar flowing reactant mixture passes through a known temperature field, while the gas composition is determined at the reactors exhaust as a function of the oven temperature. The flow reactor is operated at atmospheric pressures with temperatures up to 1,800 K. The measurements themselves are performed by decreasing the temperature monotonically at a rate of -200 K/h. With the sensitive MBMS technique, detailed speciation data is acquired and quantified for almost all chemical species in the reactive process, including radical species.

An investigation of the oxidative combustion chemistry of novel biofuels, fuel components, or jet fuels by comparison of quantitative speciation data is presented. The data can be used for kinetic model validation and enables fuel assessment strategies.This manuscript describes the atmospheric high-temperature flow reactor and demonstrates its capabilities.

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

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

化学

Wind Tunnel Experiments to Study Chaparral Crown Fires

The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low velocity fire wind tunnel where two distinct layers of fuel were constructed to represent surface and crown fuels in chaparral. Chamise, a common chaparral shrub, comprised the live crown layer. The dead fuel surface layer was constructed with excelsior (shredded wood). We developed a methodology to measure mass loss, temperature, and flame height for both fuel layers. Thermocouples placed in each layer estimated temperature. A video camera captured the visible flame. Post-processing of digital imagery yielded flame characteristics including height and flame tilt. A custom crown mass loss instrument developed in-house measured the evolution of the mass of the crown layer during the burn. Mass loss and temperature trends obtained using the technique matched theory and other empirical studies. In this study, we present detailed experimental procedures and information about the instrumentation used. The representative results for the fuel mass loss rate and temperature filed within the fuel bed are also included and discussed.

This protocol describes wind tunnel experiments designed to study the transition of a fire from the ground to the canopy of chaparral shrubs.

查帕拉尔树冠火灾风洞实验研究

The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low ...

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory setups is presented. The experiments are easily repeatable compared to operational scale experiments (pool diameter &#8805;2 m), while still featuring quite realistic in situ burning conditions of crude oil on water. Experimental conditions include a flowing water sub-layer that cools the oil slick and an external heat flux (up to 50 kW/m2) that simulates the higher heat feedback to the fuel surface in operational scale crude oil pool fires. These conditions enable a controlled laboratory study of the burning efficiency of crude oil pool fires that are equivalent to operational scale experiments. The method also provides quantitative data on the requirements for igniting crude oils in terms of the critical heat flux, ignition delay time as a function of the incident heat flux, the surface temperature upon ignition, and the thermal inertia. This type of data can be used to determine the required strength and duration of an ignition source to ignite a certain type of fresh or weathered crude oil. The main limitation of the method is that the cooling effect of the flowing water sub-layer on the burning crude oil as a function of the external heat flux has not been fully quantified. Experimental results clearly showed that the flowing water sub-layer does improve how representative this setup is of in situ burning conditions, but to what extent this representation is accurate is currently uncertain. The method nevertheless features the most realistic in situ burning laboratory conditions currently available for simultaneously studying the flammability and burning efficiency of crude oil on water.

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil

Here, we present a protocol to simultaneously study the flammability and burning efficiency of fresh and weathered crude oil under conditions that simulate in situ burning operations on the sea.

原位燃烧试验方法: 原油可燃性和燃烧效率

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory ...

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer coefficient as a function of the liquid flow rate in a transparent pipe. With certain amendments, the approach is extended to gas-liquid flows, with a particular emphasis on the effect of a single elongated (Taylor) air bubble on heat transfer enhancement. A non-invasive thermography technique is applied to measure the instantaneous temperature of a thin metal foil heated electrically. The foil is glued to cover a narrow slot cut in the pipe. The thermal inertia of the foil is small enough to detect the variation in the instantaneous foil temperature. The test section can be moved along the pipe and is long enough to cover a considerable part of the growing thermal boundary layer.
At the beginning of each experimental run, a steady state with a constant water flow rate and heat flux to the foil is attained and serves as the reference. The Taylor bubble is then injected into the pipe. The heat transfer coefficient variations due to the passage of a Taylor bubble propagating in a vertical pipe is measured as function of the distance of the measuring point from the bottom of the moving Taylor bubble. Thus, the results represent the local heat transfer coefficients. Multiple independent runs preformed under identical conditions allow accumulating sufficient data to calculate reliable ensemble-averaged results on the transient convective heat transfer. In order to perform this in a frame of reference moving with the bubble, the location of the bubble along the pipe has to be known at all times. Detailed description of measurements of the length and of the translational velocity of the Taylor bubbles by optical probes is presented.

This manuscript describes methods aimed at measuring the local instantaneous convective heat transfer coefficients in a single or two-phase pipe flow. A simple optical method to determine the length and the propagation velocity of an elongated (Taylor) air bubble moving at a constant velocity is also presented.

管道单、两相流局部瞬时对流换热的测量

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer ...

Thermal Diffusivity and the Laser Flash Method

Source: Elise S.D. Buki, Danielle N. Beatty, and <a href="https://www-jove-com.bdigitaluss.remotexs.co/author/Taylor+D._Sparks">Taylor D. Sparks</a>, Department of Materials Science and Engineering, The University of Utah, Salt Lake City, UT
The laser flash method (LFA) is a technique used to measure thermal diffusivity, a material specific property. Thermal diffusivity (&#945;) is the ratio of how much heat is conducted relative to how much heat is stored in a material. It is related to thermal conductivity (<img alt="Equation 1" src="/files/ftp_upload/10488/10488eq1v2.jpg" />), how much heat is transferred through a material due to a temperature gradient, by the following relationship:
<img alt="Equation 2" src="/files/ftp_upload/10488/10488eq2v2.jpg" /> (Equation 1)
where &#9076; is the density of the material and Cp is the specific heat capacity of the material at the given temperature of interest. Both thermal diffusivity and thermal conductivity are important material properties used to assess how materials transfer heat (thermal energy) and react to changes in temperature. Thermal diffusivity measurements are obtained most commonly by the thermal or laser flash method. In this technique a sample is heated by pulsing it with a laser or xenon flash on one side but not the other, thus inducing a temperature gradient. This temperature gradient results in heat propagating through the sample towards the opposite side, heating the sample as it goes. On the opposite side an infrared detector reads and reports the temperature change with respect to time in the form of a thermogram. An estimate of the thermal diffusivity is obtained after these results are compared and fit to theoretical predictions using a least squares model.
The laser flash method is the only method that is supported by multiple standards (ASTM, BS, JIS R) and is the most widely used method for determining thermal diffusivity.

Laser Flash Method for Measuring Thermal Diffusivity

热衍率与激光闪光方法

Source: Elise S.D. Buki, Danielle N. Beatty, and Taylor D. Sparks, Department of Materials Science and Engineering, The University of Utah, Salt Lake ...

教育

JoVE Science Education

材料工程

Constant Temperature Anemometry: A Tool to Study Turbulent Boundary Layer Flow

Source: Xiaofeng Liu, Jose Roberto Moreto, and Jaime Dorado, Department of Aerospace Engineering, San Diego State University, San Diego, California
A boundary layer is a thin flow region immediately adjacent to the surface of a solid body immersed in flow field. In this region, viscous effects, such as the viscous shear stress, dominate, and the flow is retarded due to the influence of friction between the fluid and the solid surface. Outside of the boundary layer, the flow is inviscid, i.e., there is no dissipative effects due to friction, thermal conduction or mass diffusion.
The boundary layer concept was introduced by Ludwig Prandtl in 1904, which enables significant simplification to the Navier-Stokes (NS) equation for the treatment of flow over a solid body. Inside the boundary layer, the NS equation is reduced to the boundary layer equation, while outside of the boundary layer, the flow can be described by the Euler equation, which is a simplified version of the NS equation.
<img src="/files/ftp_upload/10455/10455fig1a.jpg" />
Figure 1. Boundary layer development over a flat plate.
The simplest case for boundary layer development occurs on a flat plate at zero angle of incidence. When considering boundary layer development on a flat plate, the velocity outside of the boundary layer is constant so that the pressure gradient along the wall is considered to be zero.
The boundary layer, which naturally develops on a solid body surface, typically undergoes the following stages: first, the laminar boundary layer state; second, the transition state, and third, the turbulent boundary layer state. Each state has its own law(s) describing the flow structure of the boundary layer.
The research into the development and structure of boundary layer is of great importance for both theoretical study and practical applications. For example, boundary layer theory is the basis for calculating the skin friction drag on ships, aircraft and the blades of turbomachines. Skin friction drag is created on the body surface within the boundary layer and is due to the viscous shear stress exerted on the surface through fluid particles in direct contact with it. The skin friction is proportional to the fluid viscosity and the local velocity gradient on the surface in the surface normal direction. Skin friction drag is present on the entire surface, thus it becomes significant over large areas, such as an airplane wing. Additionally, turbulent fluid flow creates more skin friction drag. The macro-turbulent fluid motion enhances the momentum transfer within the boundary layer by bringing fluid particles with high momentum down to the surface.
This demonstration focuses on the turbulent boundary layer over a flat plate, in which the flow is irregular, such as in mixing or eddying, and the fluctuations are superimposed on the mean flow. Thus, the velocity at any point in a turbulent boundary layer is a function of time. In this demonstration, constant temperature hot-wire anemometry, or CTA, will be used to conduct a boundary layer survey. Then, the Clauser chart method will be used to calculate the skin friction coefficient in a turbulent boundary layer.

Constant Temperature Anemometry: Turbulent Boundary Layer Flow Study

恒温测量:研究湍流边界层流的工具

Source: Xiaofeng Liu, Jose Roberto Moreto, and Jaime Dorado, Department of Aerospace Engineering, San Diego State University, San Diego, California
A ...