Characterization of Reactor-Assisted Burner Flames using Ultrafast Infrared Spectroscopy

许多实际的运输燃料在所谓的低温燃烧条件下经常经历两阶段点火过程。这一特征可以加速火焰传播，这可以用来开发用于汽车和飞机的更小、更高效和更清洁燃烧的发动机。然而，在这些系统中控制火焰传播的低温燃烧物理学知之甚少。因此，该项目的主要目标是提高我们对低温燃烧的理解。将开发新的激光诊断技术，以量化运输燃料低温燃烧过程中形成的特定分子，并确定这些分子如何在与现代发动机相关的条件下加速火焰传播。该项目将提供新的激光诊断，能够表征燃烧化学和基本数据，描述低温燃烧的程度如何改变火焰的传播。由此产生的知识可以帮助工程师设计用于推进和发电的清洁和高效的燃烧系统。目前还不清楚低温燃烧的程度如何改变重烃燃料的湍流燃烧速度和湍流火焰的结构（例如，Jet-A，柴油）。由于在实际燃料中发现的大量烃类物质以及低温点火将初始反应物流重整为具有随时间变化的组成的复杂混合物的事实，该问题变得复杂。此外，了解这些火焰的行为的物理化学过程受到缺乏非侵入性诊断的阻碍。该研究计划将通过以下方式填补这些空白：1）开发具有亚皮秒分辨率的新型超快中远红外激光诊断技术，2）将其应用于表征由正十二烷和Jet-A燃料的反应堆辅助燃烧器火焰。超快脉冲的使用将使大部分的中远红外光谱能够在亚皮秒时间尺度上被询问，同时还能够获得分子光谱的无碰撞测量。这些属性将被利用，以提供简化的多参数表征的反应物流和湍流火焰产生的一种新型的反应器辅助燃烧器。这种方法将提供新的基本数据和洞察力，关于如何温度和组成的反应物流改变湍流火焰传播的条件相关的现代推进engine.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

Many practical transportation fuels often undergo a two-stage ignition process under the so-called low-temperature combustion conditions. This feature can accelerate flame propagation which could be exploited to develop smaller, more efficient, and cleaner burning engines for automobiles and aircrafts. However, the low-temperature combustion physics governing flame propagation in these systems is poorly understood. Thus, a primary goal of this project is to improve our understanding of low-temperature combustion. New laser diagnostics will be developed to quantify the specific molecules that are formed during low-temperature combustion of transportation fuels and to determine how these molecules accelerate flame propagation at conditions relevant to modern engines. This project will provide new laser diagnostics, capable of characterizing combustion chemistry, and fundamental data, describing how the extent of low-temperature combustion alters the propagation of flames. The resulting knowledge can help engineers design clean and efficient combustion systems for propulsion and power generation.It is not well understood how the extent of low-temperature combustion alters the turbulent burning velocity and structure of turbulent flames fueled by heavy hydrocarbons (e.g., Jet-A, diesel). This issue is complicated by the large number of hydrocarbon species found in practical fuels and the fact that low-temperature ignition reforms the initial reactant stream into a complex mixture with a time-varying composition. Further, understanding the physicochemical processes governing the behavior of these flames is impeded by the lack of non-intrusive diagnostics. This research program will fill these gaps through: 1) the development of novel ultrafast mid- to far-infrared laser diagnostics with sub-picosecond resolution and 2) their application to characterizing reactor-assisted burner flames fueled by n-dodecane and Jet-A. The use of ultrafast pulses will enable large portions of the mid- to far-infrared spectrum to be interrogated on sub-picosecond timescales, while also enabling collision-free measurements of molecular spectra to be acquired. These attributes will be exploited to provide simplified multi-parameter characterization of the reactant stream and turbulent flames produced by a novel reactor-assisted burner. This approach will provide new fundamental data and insight regarding how the temperature and composition of the reactant stream alters turbulent flame propagation at conditions relevant to modern propulsion engines.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.