Name: wind tunnel experiments to study chaparral crown fires
Uploaded: 2017-11-14T14:00:00
Description: Watch this Scientific Journal Video about Wind Tunnel Experiments to Study Chaparral Crown Fires at JoVE.com

作者要感谢本杰明 Sommerkorn, 加布里埃尔杜邦, 杰克 Eggan 和 Chirawat Sanpakit 谁协助在这里提出的实验。珍妮特 Cobian Iñiguez 承认支持由美国宇航局 MUREP 机构研究机会 (米洛) 授予号码 NNX15AP99A。这项工作也由美国农业部/USDI 国家防火计划通过美国农业部森林服务, PSW 研究站和加州大学河滨分校的协议资助。

警告: 由于以下协议中的几个步骤涉及有可能导致损伤的活动, 因此应确保按照已建立的安全协议 (包括防火) 使用适当的个人防护设备 (PPE)耐磨的衣服和防护眼镜. 
 1. 皇冠燃油床负载电池检测安装程序 <ol> <li> 通过将双弹簧门扣 (参见 材料表 ) 通过钳位和 #39 的销孔来修改 4 C 钳 (参见 图 2 )。使用扣来悬挂皇冠燃料床. </li>
	<li> 使用一组?...

<ol>
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在整个实验中, 测量高燃料质量的能力是这项技术的主要优点之一。以前的研究查帕拉尔火灾的重点是只在树冠火启动或只在表面传播, 但不是两者兼而有之。这些研究已经量化了在树冠层点火的可能性, 并离开了对未来工作的研究23。我们的方法允许测量的质量损失, 温度分布和火焰几何的两个层涉及灌木树冠火点火和蔓延。它提供了一种从质量损失率间接推断能量通量的方法。...

在 2016年, 加利福尼亚州总共经历了6986场荒地大火, 消耗了564835英亩的1, 造成数百万美元的损失, 并冒着数百人的健康风险。由于区域地中海气候, 主要燃料来源为这些火是查帕拉尔植被社区2。火灾蔓延在查帕拉尔可以被认为是一个皇冠火, 因为主要的燃料, 烧伤是提升3。共同存在与主要地居住的冠层数, 是死的表面燃料层数, 包括铸造的叶子、分支和草本植物生长在和在各自的灌木之间。火将更容易启动在死表面燃料层。一旦表面火点燃, 火可能转移到冠层, 在火释放的能量急剧增加。虽然查帕拉尔火灾通常被模拟为火灾蔓延在深表面燃料4, 有有限的研究查帕拉尔火灾的树冠火灾。

查帕拉尔的树冠特征, 包括叶片颗粒形状, 与北方针叶林不同, 其中大部分研究都是在那里发生的。众多的实验室和野外规模研究已经调查了野火动力学的各个方面6,5,7,3,8,9,10 ,11,12。在实验室实验领域, 有几项研究分析了风和燃料性质等参数对查帕拉尔冠火行为的影响。Lozano7检测了在两个独立的树冠燃料层存在下的顶火起爆特性。在 Tachajapong et al.3, 在风洞内燃烧了离散表面和树冠层, 并进行了表面火灾的表征。只有冠火起爆被充分描述留下充分的分析传播为未来工作。Li et al.11报告了火焰的传播, 虽然单查帕拉尔灌木。在相关工作中, 克鲁兹et al.10,9开发了一个模型来预测在展开的表面火之上的针叶树叶的点火。对查帕拉尔燃料的燃烧特性进行了研究, 并对散装燃料和个体叶片的试验进行了探讨13,14,15,16。Dupuy et al.13通过在圆柱筐中燃烧燃料, 研究了松松树针和精益的燃烧特性。他们观察到, 在这些燃料中, 火焰高度通过2/5 幂定律与热释放率有关, 正如先前在文献1718中所报告的那样。Sun et al.14在类似的圆柱筐中燃烧查帕拉尔燃料, 以分析三查帕拉尔燃料的燃烧特性: chamise (Adenostoma 三)、ceanothus (ceanothus crassifolius) 和 manzanita (Arctostaphylos glandulosa)。
在上述实验室研究的结果的激励下, 我们的目的是提出一种方法来描述在表面和灌木树冠层的传播。此外, 我们的目的是澄清一些关键的特征, 决定了表面-冠层相互作用的程度。为此, 我们开发了实验实验室方法, 研究在荒地表面燃料燃烧的垂直转变为在高架灌木燃料中蔓延的火灾。在这些类型的火灾中, 将火翻译成树冠, 被称为加冠, 在适当的条件下可持续传播。一般而言, 查帕拉尔的火灾行为是由地形、天气和燃料19决定的。结果表明, 风影响能量释放率在燃料5,3,8,20。
多孔燃料中的火蔓延可以看作是一系列的过渡或阈值, 必须跨越才能成功21。精力充沛地, 燃料微粒点燃, 如果它接受的热量的数量结果在气体的混合物成功地反应与氧气。当燃烧粒子的热量点燃相邻的燃料粒子时, 产生的火焰就会扩散。如果火势能够跨越可燃燃料元件之间的空隙, 就会蔓延到地面。如果火焰的表面火能够垂直传播到树冠的灌木和树木, 火灾行为的重大变化, 包括增加的热释放率, 往往被观察到, 由于更大的可用性燃料。荒地火灾中的热能动力学包括几个尺度, 从非常大的规模, 如在大型火灾, 往往需要气候建模, 小规模需要化学尺度动力学建模。在这里, 我们处理实验风洞尺度行为建模;对于化学尺度的纤维素燃烧研究, 读者被称为工作, 如沙利文et al.22
自2001年以来, 我们进行了各种实验, 检查了一些实验室规模的能量阈值23,8,24,25,26, 27, 重点是与查帕拉尔相关的带电燃料。虽然室外测量的火可以提供更逼真的结果, 受控环境的风洞允许划定各种参数的影响。例如, 控制风对于查帕拉尔的树冠火灾尤其重要, 例如在南加州, foehn 类型的风, 称为圣安娜风, 是典型的火灾事件的驱动因素。由于本文所述方法的主要动力是研究风和其他受控参数对查帕拉尔火灾蔓延的影响, 本研究在实验室规模风洞中进行。读取器由 Silvani et al.定向到工作28用于现场测量查帕拉尔火灾中的温度, 类似于此处所示。有关风对火势蔓延影响的实地测量, 请参阅莫兰迪et al.29
通过量化概率, 对影响查帕拉尔燃料扩散的几个参数进行了实验分析火传播成功在高架燃料床8。目前的实验研究涉及的方法是开发的研究查帕拉尔树冠火灾蔓延的模拟表面燃料和皇冠燃料在测试段的低速风洞。表面燃料是建模与精益求精 (干碎木材)。表面燃料床被安置在风洞的地面水平在标准尺度 (参见图 1)。代表顶部燃料床, 一个燃料床与 chamise 被放置在表面燃料床通过悬挂燃料从一个平台上安装在风洞框架 (见图 1)。两个燃料床都被检测温度和质量损失测量;火焰几何学是从实验录像中获得的。测量的参数包括质量损失率、燃料含水量和空气相对湿度。控制的参数是风存在, 表面燃料床和树冠燃料床之间的距离, 以及表面燃料的存在。测量的质量损失率可以用来计算热释放率, 这是定义为: 
<img alt="Equation 1" src="/files/ftp_upload/56591/56591eq1.jpg"> 其中h是燃料燃烧的热量, m是燃料质量, t是时间。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56591/56591fig1.jpg"> 
图 1: 风洞实验装置.皇冠燃料床的位置, 地面燃料床, 和隧道风扇已被标记为方便。地面燃料床被安置在风洞的地面水平在标准标度。代表顶部燃料床, chamise 的燃料床被放置在地面燃料床上, 悬挂燃料从一个平台上安装在风洞框架。<a href="//ecsource.jove.com/files/ftp_upload/56591/56591fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
实验的重点是了解查帕拉尔冠火的行为, 特别是点火, 火焰传播和传播的机制, 火焰锋速度, 和燃料消耗率。为了研究表面火和冠火之间的相互作用, 六配置的表面和顶部燃料床与没有应用风流, 已被烧毁的风洞: 冠燃料只有和没有风 (2), 树冠和表面燃料床分离两个距离与和没有风 (4)。表 1总结了6实验类的实验配置。在表中, 表面燃料层参数表示在试验过程中是否存在表面燃料, 风参数指的是风的存在, 树冠的高度是指顶部燃料床底部与表面底部之间的距离燃料床每项试验都测量了燃料湿度, 但不受控制, 平均燃料含水量为 48%, 而最小和最大值分别为18% 至68%。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>类</td>
			<td>表面燃料床</td>
			<td>风</td>
			<td>皇冠高度</td>
		</tr>
		<tr>
			<td>一个</td>
			<td>缺席</td>
			<td>无风</td>
			<td>60或70厘米</td>
		</tr>
		<tr>
			<td>b</td>
			<td>缺席</td>
			<td>1毫秒-1</td>
			<td>60或70厘米</td>
		</tr>
		<tr>
			<td>c</td>
			<td>目前</td>
			<td>无风</td>
			<td>60厘米</td>
		</tr>
		<tr>
			<td>d</td>
			<td>目前</td>
			<td>无风</td>
			<td>70厘米</td>
		</tr>
		<tr>
			<td>e</td>
			<td>目前</td>
			<td>1毫秒-1</td>
			<td>60厘米</td>
		</tr>
		<tr>
			<td>f</td>
			<td>目前</td>
			<td>1毫秒-1</td>
			<td>70厘米</td>
		</tr>
	</tbody>
</table>
表 1: 实验配置在这里, 表面燃料床参数表示在试验过程中是否存在表面燃料, 风参数指的是风的存在, 树冠的高度是指顶部燃料床底部与表层燃料床底部之间的距离。
电子秤测量表面燃料质量, 我们开发了一个自定义质量损失系统的冠层。该系统由单独的负载单元连接到悬挂的燃料床的每个角落。消费级摄像机记录了视觉火焰;图像处理的视觉数据使用自定义脚本生成的火焰特性, 包括高度和角度。开发了一个程序, 将视频帧从 RGB (红/绿/蓝) 编码转换为黑白, 通过一个光强阈值的过程。火焰的边缘是从黑白视频帧中获得的。最大火焰高度被定义为火焰边缘的最高点, 同时也获得了火焰的瞬时高度。在图像中, 火焰的高度是从燃料床的底部测量到火焰的最大垂直点。所有的处理代码以及为该协议设计的仪表控制接口都是作者通过他们的软件访问站点提供的。在当地收割现场燃料, 并在24小时内进行实验性烧伤, 减少水分流失。热电偶阵列记录了在风流向方向的燃料床温度, 从而能够计算传播速率。图 1显示了燃料床设置的示意图以及热电偶的布置。实验协议的细节如下。

<table>
	<tbody>
		<tr>
			<td>Wind Tunnel Instrumentation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>cDAQ-9178 CompactDAQ Chassis</td>
			<td>National Instruments</td>
			<td>781156-01</td>
			<td></td>
		</tr>
		<tr>
			<td>NI-9213 C Series Temperature Input Module</td>
			<td>National Instruments</td>
			<td>785185-01</td>
			<td></td>
		</tr>
		<tr>
			<td>NI SignalExpress for Windows</td>
			<td>National Instruments</td>
			<td>779037-35&#160;</td>
			<td>Newest version, older version used for experiment</td>
		</tr>
		<tr>
			<td>High Temperature Nextel Insulated Thermocouple Elements</td>
			<td>Omega</td>
			<td>XC-24-K-18</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermocouple Extension Wire with Polyvinyl Coated Wire and Tinned Copper Overbraid</td>
			<td>Omega</td>
			<td>EXPP-K-24S-TCB-P</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra High Temperature Miniature Connectors</td>
			<td>Omega</td>
			<td>SHX-K-M</td>
			<td></td>
		</tr>
		<tr>
			<td>CompuTrac MAX 2000XL&#160;</td>
			<td>Arizona Instruments</td>
			<td>MAX-2000XL</td>
			<td>Discontinued, Newer Model Out</td>
		</tr>
		<tr>
			<td>Kestrel 3000 Pocket Weather Meter</td>
			<td>Nielsen-Kellerman</td>
			<td>0830</td>
			<td></td>
		</tr>
		<tr>
			<td>Satorius CPA 34001S&#160;</td>
			<td>Sartorius</td>
			<td>25850314</td>
			<td>Discontinued Model</td>
		</tr>
		<tr>
			<td>5 Kg Micro Load Cell (X4)</td>
			<td>Robotshop.com</td>
			<td>RB-Phi-118</td>
			<td>Strain Gauge Load Cell</td>
		</tr>
		<tr>
			<td>Phidget PhidgetBridge Wheatstone Bridge Sensor Interface</td>
			<td>Robotshop.com</td>
			<td>RB-Phi-107</td>
			<td>Interfaces with 4 load cells, performs signal amplification</td>
		</tr>
		<tr>
			<td>#2 Stainless S-Biner (X4)</td>
			<td>Home Depot</td>
			<td>SB2-03-11</td>
			<td>Dual spring gate carabiners used to mount load cells</td>
		</tr>
		<tr>
			<td>2 in. Malleable Iron C-Clamp</td>
			<td>Home Depot</td>
			<td># 4011</td>
			<td>Used to mount load cells</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Personal Protective Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Wildland Firefighter Nomex Shirt</td>
			<td>GSA Advantage</td>
			<td>SH35-5648</td>
			<td></td>
		</tr>
		<tr>
			<td>Fireline 6 oz Wildland Fire Pants</td>
			<td>GSA Advantage</td>
			<td>139702MR SEV16</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Fuels</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chamise</td>
			<td>Collected in situ</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Natural Shredded Wood Excelsior &#8211; Natural Coarse 50 lbs bail</td>
			<td>Paper Mart</td>
			<td>21-711-88</td>
			<td></td>
		</tr>
		<tr>
			<td>Bernzomatic UL100 Basic Propane Torch Kit</td>
			<td>Home Depot</td>
			<td>UL100KC</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol</td>
			<td>Convenience store</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Video and Photography</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nikon D3000 10.2-MP DSLR camera with DX-format sensor and 3x 18x55mm Zoon-NIKKOR VR Image Stabilization Lens</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sony Handycam Camcorder DCR-SX85</td>
			<td>Amazon.com</td>
			<td>DCR-SX85</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NI LabView</td>
			<td>National Instruments</td>
			<td>Student Version</td>
			<td>Used for instrument control and interfacing</td>
		</tr>
		<tr>
			<td>MATLAB Student Version (MATLAB_R2014a)</td>
			<td>Mathworks</td>
			<td>Student Version&#160;</td>
			<td>Used for data post-processing including image processing</td>
		</tr>
	</tbody>
</table>

wind tunnel experiments to study chaparral crown fires

本协议提出了一种实验室技术, 旨在研究查帕拉尔冠火点火和蔓延。在一个低速风洞中进行了实验, 其中两个不同的燃料层被建造来代表查帕拉尔中的表面和树冠燃料。Chamise, 一种常见的查帕拉尔灌木, 包括活冠层。用精益 (碎木) 建造的死燃料表面层。我们开发了一种方法来测量两个燃料层的质量损失、温度和火焰高度。热电偶放置在每层估计温度。摄像机捕捉到了可见的火焰。数字图像后处理产生火焰特性, 包括高度和火焰倾斜。自定义冠质量损失仪器开发了 in-house 测量了冠层质量的演变在烧伤期间。利用技术匹配理论和其他实证研究得出的质量损失和温度趋势。在本研究中, 我们提供了详细的实验程序和有关仪器使用的信息。并对燃料层中燃料质量损失率和温度的代表性结果进行了讨论。

从视频数据中获得了树冠和表面火焰高度数据。实验的典型火焰高度趋势在图 6中介绍。火焰高度行为跟随在太阳中发现et al.14
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/56591/56591fig6.jpg"> 
图 6: 估计的顶部火焰高度.这里U = 1 米/秒, 表面-冠分离d = 70 厘...

Watch this Scientific Journal Video about Wind Tunnel Experiments to Study Chaparral Crown Fires at JoVE.com

Wind Tunnel Experiments to Study Chaparral Crown Fires

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