Coupled Mixing and Auto-Ignition Dynamics of Turbulent Fuel Jets Issuing into Hot and Vitiated Oxidizing Environments

1605136 -Sutton广泛的工程系统，如运输和发电平台，依赖于将湍流燃料流注入高温氧化环境。 在一定的混合物和温度条件下，会发生自燃。 诸如柴油发动机和高速超音速燃烧冲压喷气发动机/冲压喷气发动机的系统依靠自动点火来实现点火和火焰稳定。 其他系统，包括燃气涡轮发动机和火花点火发动机，被设计成防止自动点火，以避免重大和/或灾难性的损坏。 对于这两种情况，都非常希望了解瞬态自燃过程的物理规律。 湍流是非常复杂的，并且当与控制自燃的化学反应耦合时，形成高度动态的系统，其中湍流混合对反应化学具有直接影响。 在这个项目中，时间分辨测量燃料/氧化剂的混合，温度和物种将使用先进的激光诊断，表征的流动和化学条件下实现自燃核心形成湍流燃料喷射。 这项研究的影响将是深远的，从对自燃动力学的新的物理理解到评估数值模拟和模型。 该项目还将帮助培训一名研究生和指导一名博士后研究员。 此外，这个项目的一个独特的方面是一个正式的直接研究生到本科生的指导计划，其中研究生是合作伙伴，并指导本科荣誉学生的实施。 PI还将与当地一所小学合作开展K-12外展活动，为年轻学生提供STEM相关主题的信息，灵感和倡议。 总体主题，如燃烧，发动机和激光，为年幼的孩子提供了令人兴奋的主题，可以帮助建立对科学和技术的终身兴趣的基础。 拟议的研究将是变革性的事实，湍流混合，低温化学和？热吗将首次详细研究点火核的形成。 高速（10至100 kHz采集速率）激光诊断将用于测量混合物分数，温度和CH 2 O/OH浓度后，通过自动点火湍流燃料喷射。 具体的研究贡献包括量化关键的时间依赖性过程，这些过程导致观察到的自燃拓扑结构，包括湍流混合修改自燃拓扑结构的机制和低温化学的作用（例如，CH 2 O）对点火核形成的影响。由于自燃过程的瞬态和空间间歇性，多维的，时间的记录是必要的，以表征流场标量在点火核心网站。 这些测量将被用来确定混合物分数，CH 2 O（低温化学）和OH（热点火内核）之间的时空相关性，以及开发新的统计的混合物分数，温度和标量耗散条件下的点火内核的位置参数化的最可能的条件导致自燃。 建议的测量将在广泛的试验条件下进行，检查不同雷诺数（Damköhler）数，燃料类型，氧化剂成分和温度的影响。

1605136 - SuttonA broad range of engineering systems such as transportation and power-generation platforms rely on the injection of a turbulent fuel stream into a high-temperature, oxidizing environment. Under certain mixture and temperature conditions, auto-ignition will occur. Systems such as diesel engines and high-speed scramjets/ramjets rely on auto-ignition for achieving ignition and flame stabilization. Other systems, including gas-turbine and spark-ignition engines are designed to prevent auto-ignition to avoid significant and/or catastrophic damage. For either of these scenarios it is highly desired to understand the physics governing the transient auto-ignition process. Turbulent flows are very complex and when coupled to the chemical reactions governing auto-ignition, a highly dynamic system is formed where turbulent mixing has a direct effect on the reaction chemistry. In this project, time-resolved measurements of fuel/oxidizer mixing, temperature, and species will be made using advanced laser diagnostics, characterizing the flow and chemical conditions necessary for achieving auto-ignition kernel formation under turbulent fuel injection. The impact of the research will be far-reaching, ranging from a new physical understanding of auto-ignition dynamics to assessing numerical simulations and models. This project also will aid in the training of a graduate student and mentoring of a post-doctoral researcher. In addition, a unique aspect of this project is the implementation of a formal direct graduate-to-undergraduate mentoring program, where a graduate student is partnered with and mentors an undergraduate honors student. The PI also will partner with a local elementary school for K-12 outreach, equipping young students with information, inspiration, and initiative in STEM-related topics. The overarching topics, such as combustion, engines, and lasers, provide exciting themes for younger children and can help build the foundation for a life-long interest in science and technology. The proposed research will be transformative in the fact that the dynamic coupling between turbulent mixing, low-temperature chemistry and ?hot? ignition kernel formation will be examined in detail for the first time. High-speed (10 to 100 kHz acquisition rate) laser diagnostics will be used to measure the mixture fraction, temperature, and CH2O/OH concentrations following turbulent fuel injection through auto-ignition. Specific research contributions include quantification of key time-dependent processes which lead to the observed auto-ignition topology including the mechanisms in with turbulent mixing modifies auto-ignition topology and the role of low-temperature chemistry (e.g., CH2O) on ignition kernel formation. Due to the transient and spatially-intermittent nature of the auto-ignition process, multi-dimensional, temporal records are necessary to characterize the flow field scalars at the ignition kernel sites. These measurements will be used to determine space-time correlations between mixture fraction, CH2O (low-temperature chemistry) and OH (hot ignition kernel) as well develop new statistics of the mixture fraction, temperature, and scalar dissipation conditioned on the ignition kernel location for parameterization of the most probable conditions leading to auto-ignition. The proposed measurements will be carried out across a broad range of test conditions, examining the effects of varying Reynolds (Damköhler) number, fuel type, and oxidizer composition and temperature.