CAREER: Controlling Mechanisms of Dust Layer Ignition and Flame Propagation in Dust Clouds

0846764 Rangwala该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该职业奖的研究重点是发展对粉尘火灾和爆炸的基本科学理解。 可燃粉尘层可被温度足够高的表面点燃，由此产生的火灾可造成生命和财产的巨大损失。在某些情况下，这些过程是逐步升级的事件链的第一步，可能导致气体和粉尘爆炸。 粉尘爆燃的发生和传播是一个非常复杂的现象，这是由于固体颗粒和气体火焰阵面之间的相互作用。与预混气体爆燃相比，粉尘-氧化剂爆燃取决于挥发分的演化速率、挥发分与氧化剂的混合、颗粒与气相氧化的耦合以及火焰与周围环境的辐射能量交换。正在开发详细的实验以测量具有不同燃料/氧化剂比率、颗粒尺寸和粉尘类型的粉尘-氧化剂火焰的点火和传播速率。在工作的一部分，修改后的ASTM E2021热表面装置将被用来分析参数控制粉尘层的点火。这些参数将被用来预测点燃的灰尘存款在一个现实的几何形状，如二维楔和三维角落。分析了粉尘粒径和氧气浓度对粉尘层着火的影响。 与此同时，将探讨预混粉尘氧化剂火焰的结构，以分析火焰在颗粒流中的传播。一个预混马赫Hebra燃烧器与适当的修改，以允许燃烧的均匀混合物的灰尘和氧化剂将被用来研究一个稳定的灰尘氧化剂火焰的结构。通过激光多普勒风速仪测量的层流燃烧速度将用于表征石松（30 µm）、聚甲基丙烯酸甲酯（300 nm、10µm、30µm和60µm）、煤（15-38µm、38-44 µm和44- 55µm）和铝（10µm）粉末的质量燃烧速率。这项实验研究的结果将进一步用于验证粉尘云中火焰传播的数值计算流体力学模型。这项研究也意味着在火灾科学和工程领域的基础研究的新机会的催化剂。 该教育计划将通过两种方式提高全世界学校和大学对消防科学和工程学科的认识：（a）建立以大学生为重点的国家和国际项目中心，在与火灾有关的基础研究领域举办为期三个月的独立学习小组;（B）与当地高中和中学教师互动，一周的暑期课程，让学生产生对基础科学的兴趣。学生将在WPI消防实验室获得实践经验，并从当地消防员那里了解消防安全。这项建议的教育工作预计将提高人们对火灾科学领域的认识，而研究计划将有助于从目前基于工程的经验模型转向基于基本理论的分析和实验。

0846764RangwalaThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This research in this CAREER award focuses on developing fundamental scientific understanding of dust fires and explosions. Combustible dust layers can be ignited by a surface whose temperature is sufficiently high and the resulting fires can cause large losses in lives and property. In some cases these processes are the first step towards an escalating chain of events that can lead to both gas and dust explosions. Initiation and propagation of dust deflagrations are extremely complex phenomena due to the interaction between solid particles and the gaseous flame front. In comparison with premixed gas deflagration, a dust-oxidizer deflagration depends on the rate of evolution of volatiles, the mixing of these volatiles with the oxidizer surrounding the particles, coupling of the particles and gas-phase oxidation, and radiative energy exchange between the flame and its surroundings.To identify mechanisms and controlling parameters for dust-layer ignition and deflagration, detailed experiments are being developed to measure ignition and the rate of propagation of a dust-oxidizer flame with different fuel/oxidizer ratios, particle sizes, and dust types. In one part of the work, a modified ASTM E2021 hot-surface apparatus will be used to analyze parameters controlling the ignition of dust layers. These parameters will then be used to predict ignition of a dust deposit in a realistic geometry such as a two-dimensional wedge and a three-dimensional corner. Influence on particle size and oxygen concentration on dust layer ignition will also be analyzed. In parallel, the structure of a premixed dust-oxidizer flame will be explored to analyze flame propagation in particle-laden flows. A premixed Mache Hebra burner with suitable modifications to allow burning of a homogenous mixture of dust and oxidizer will be used to study the structure of a stabilized dust-oxidizer flame. Laminar burning velocity measured by Laser Doppler Anemometry will be used to characterize the mass burning rate of Lycopodium (30 µm), polymethyl methacrylate (300nm, 10µm, 30µm, and 60µm), coal (15-38µm, 38-44 µm and 44- 55µm), and aluminum (10µm) powders. The results of this experimental study will be further used to validate numerical CFD models for flame propagation in dust clouds.The research is also meant to act as a catalyst for new opportunities of fundamental research in the field of fire science and engineering. The education plan will increase the awareness in schools and universities world-wide toward the discipline of fire science and engineering in two ways: (a) Establishing national and international project centers focused towards undergraduate students for three-month independent study groups in areas of fundamental fire-related research and (b) Interacting with local high-school and middle-school teachers to develop a three-week summer course for their students to generate an interest in basic science. Students will get hands-on experience at the WPI fire laboratory and learn about fire safety from local firefighters. The educational efforts of this proposal are expected to increase awareness of the field of fire science, while the research program will help in bringing a shift from the present engineering-based empirical models to fundamental theory-based analysis and experimentation.