Quantifying the Combustion Characteristics of Hydrofluorocarbons

卤代烃被广泛用作制冷剂和灭火剂。目前该行业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。已确定的环境友好的替代品是氢氟烃，这种物质易燃，有火灾危险。其中一些氢氟碳化物已经被用作制冷剂，尽管它们的燃烧行为还没有得到很好的描述。被测试的候选灭火剂被发现促进燃烧，而不是抑制燃烧。该项目旨在通过新的实验来量化氢氟烃的反应性。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对工业中氢氟碳化合物的选择和采用以及安全规程的制定起到重要作用。该项目不仅将促进对这些外来化合物燃烧行为的了解，还将促进对其他基本燃烧方面的了解，如重力引起的火焰加速。拟议的项目还将为本科生创造实践和实验研究经验的机会，并将导致开发教育模块，这些模块将用于加强课程并激励K-12学生。与碳氢化合物相比，氢氟烃的易燃性较轻，这使得量化其反应性具有挑战性。火焰速度将通过克服与浮力诱导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它们的反应性，主要是基于氟的自由基的反应，并创建对开发化学动力学模型有价值的档案数据。由于其温和的反应性，重力驱动的不稳定性增长预计将显著影响氢氟碳/空气火焰的动力学。直接的数值模拟将被用来调查不稳定性增长对火焰动力学的影响，由热膨胀和非均匀扩散引起的重力驱动和内在火焰前沿不稳定性之间的耦合，以及由此产生的火焰加速。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.