Resolving the Shortcomings in Modern NH3 Kinetics Models using Detailed Species Time Histories and Direct Rate Measurements

由于其零碳含量和既定的生产方法，氨（NH3）作为发电和推进的燃料引起了人们的极大兴趣。在过去的几年里，世界各地进行了许多研究，试图了解和预测其燃烧化学。然而，目前用于预测氨燃烧行为的模型之间存在很大差异，没有一个模型可以匹配整个现有数据集，因此进展是渐进的，有时不一致。该项目将解决目前的许多差异，并提高氨化学模型的可靠性和预测能力。PI和他的团队将利用最先进的激光诊断和实验室设施来测量目前缺失的模型参数。对氨等氢基燃料来源的研究最终将有助于减少全球温室气体的产生。这个多学科的研究项目将允许来自机械工程和物理化学背景的研究生每天进行互动。PI实验室和涡轮机械实验室的本科生研究计划正在进行的互补项目将扩大参与者的数量，同时让本科生接触到使用激光进行燃烧化学研究。虽然近年来在氨化学动力学方面已经产生了许多结果，但大多数数据都是用于表征全球反应性，即点火延迟时间和层流火焰速度。然而，提高洞察力的NH3的化学动力学，可以通过专注于测量详细的物种在激波管的时间历程。这样的测量可以定制的氧化机制的验证和速率系数的直接测量。该项目将测量物种的时间历程，用于机理诊断和直接测量NH3氧化机理中关键反应的速率常数。通过使用激波管来产生高温条件（1000 - 2500 K），将执行NH 2、NH3、H2O和N2 O的激光吸收测量，并且将以高精度测量至少2个重要反应的反应速率。该项目的成功完成将推进对氨氧化的基本认识和预测。通过关注重要物种的浓度时间历史可以提供的详细信息，可以解决目前存在于NH3化学动力学模型之间的许多差异。在燃烧温度下直接测量单个临界反应的速率系数将进一步提高氨燃烧详细动力学机制的准确性。该奖项反映了NSF的法定使命，并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，被认为值得支持。

Because of its zero-carbon content and established production methods, ammonia (NH3) has drawn much interest as a fuel for power generation and propulsion. Many research studies worldwide have been conducted over the past few years in an attempt to understand and predict its combustion chemistry. However, there are wide discrepancies among current models that are used to predict the combustion behavior of ammonia, and none can match the entire existing data set, so progress has been incremental and sometimes inconsistent. This project will resolve much of the current discrepancies and increase the reliability and predictive capability of ammonia chemistry models. The PI and his team will utilize state-of-the-art laser diagnostics and lab facilities to measure the model parameters that are currently missing. Research into hydrogen-based fuel sources such as ammonia will ultimately help to reduce the production of greenhouse gases globally. This multidisciplinary research project will allow graduate students from both mechanical engineering and physical chemistry backgrounds to interact on a daily basis. Ongoing, complementary projects in the PI’s lab and the Turbomachinery Laboratory’s undergraduate research program will broaden the number of participants while giving undergraduate students exposure to research using lasers for combustion chemistry.Although many results have been generated in recent years on ammonia chemical kinetics, most of the data have been for characterization of global reactivity, namely ignition delay times and laminar flame speeds. However, improved insight into the chemical kinetics of NH3 can be made by focusing on the measurement of detailed species time histories in a shock tube. Such measurements can be tailored for the validation of oxidation mechanisms and the direct measurement of rate coefficients. This project will measure species time histories for mechanism diagnosis and for making direct measurements of the rate constants of key reactions in the NH3 oxidation mechanism. By using a shock tube to produce the high-temperature conditions (1000 – 2500 K), laser absorption measurements of NH2, NH3, H2O, and N2O will be performed, and the reaction rates of at least 2 important reactions will be measured with high accuracy. The successful completion of the project will advance the fundamental understanding and prediction of ammonia oxidation. By focusing on the detailed information that concentration time histories of important species can provide, many of the discrepancies that currently exist among NH3 chemical kinetics models can be resolved. Direct measurements of the rate coefficients of individual, critical reactions at combustion temperatures will further improve the accuracy of detailed kinetics mechanisms for ammonia combustion.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.