Quantifying the Combustion Characteristics of Hydrofluorocarbons

卤代烃广泛用作制冷剂和灭火剂。目前工业上使用的化合物具有很大的全球变暖潜力和/或臭氧消耗潜力。已确定的对环境更友好的替代品是氢氟碳化合物，氢氟碳化合物易燃，有火灾风险。这些氢氟碳化物中的一些已经被用作制冷剂，尽管它们的燃烧行为还没有得到很好的表征。经过测试的候选灭火剂被发现促进燃烧而不是抑制燃烧。本项目旨在通过新的实验来量化氢氟碳化合物的反应性。此外，还将进行计算，以调查在意外泄漏和随后着火的情况下与这些化合物有关的火灾风险。这些研究的结果有望在氢氟碳化合物在工业中的选择和采用以及安全协议的制定方面发挥重要作用。该项目不仅将推进对这些奇异化合物的燃烧行为的理解，还将推进对其他基本燃烧方面的理解，例如重力引起的火焰加速。拟议的项目还将为本科生创造机会，让他们有动手的实验研究经验，并将导致教育模块的开发，这将用于加强课程以及激励K-12学生。与碳氢化合物相比，氢氟碳化合物是轻度易燃的，这使得量化它们的反应性具有挑战性。火焰速度将通过克服与浮力引起的流动和辐射热损失相关的挑战来测量，分别使用实验室规模的落塔实验和详细的计算模型。明智地进行参数研究，将能够阐明和量化的反应，主要是氟基自由基的反应，并创建档案数据的化学动力学模型的发展有价值的。由于其温和的反应性，重力驱动的不稳定性增长预计将显着影响氢氟碳化合物/空气火焰的动态。直接数值模拟将用于研究不稳定性增长对火焰动力学的影响，重力驱动和热膨胀和非等扩散导致的固有火焰前缘不稳定性之间的耦合，以及由此产生的火焰加速。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Halogenated hydrocarbons are extensively used as refrigerants and fire suppressants. Compounds that are currently used by the industry have large global warming potential and/or ozone depletion potential. Environmentally friendlier alternatives that have been identified are hydrofluorocarbons, which are flammable and pose fire risks. Some of these hydrofluorocarbons are already in use as refrigerants even though their combustion behavior is not well-characterized. Candidate fire suppressants that were tested were found to promote combustion instead of inhibiting it. This project aims to quantify the reactivity of hydrofluorocarbons through novel experiments. Furthermore, computations will be performed to investigate the fire risk associated with these compounds in the case of accidental leakage and subsequent ignition. The results from these studies are expected to play an important role in the selection and adoption of hydrofluorocarbons in the industry and the development of safety protocol. The project will not only advance the understanding of the combustion behavior of these exotic compounds but also of other fundamental combustion aspects such as gravity-induced acceleration of flames. The proposed project will also create opportunities for undergraduate students to have hands-on, experimental research experience and will result in the development of education modules, which will be used to strengthen courses as well as inspire K-12 students.Hydrofluorocarbons are mildly flammable compared to hydrocarbons, which makes quantifying their reactivity challenging. Flame speeds will be measured by overcoming challenges associated with buoyancy-induced flow and radiation heat loss, using a lab-scale drop tower experiment and detailed computational models, respectively. Judiciously performed parametric studies will enable the elucidation and quantification of their reactivity, dominated by reactions of fluorine-based radicals, and create archival data valuable for the development of chemical kinetic models. Due to their mild reactivity, gravity-driven instability growth is expected to significantly influence the dynamics of hydrofluorocarbon/air flames. Direct Numerical Simulations will be performed to investigate the effect of instability growth on flame dynamics, the coupling between the gravity-driven and intrinsic flame front instabilities resulting from thermal expansion and non-equidiffusion, and the resulting flame acceleration.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.