EAGER: Investigating Super-Heated Urea for NOx Reduction for Low Temperature Combustion Engine Application

氮氧化物(NOx)是柴油机排放的主要污染物之一，其对健康和环境的影响也是有据可查的。已经投入了认真的努力，通过清理废气和优化燃烧来减少排放。有趣的是，在效率和污染之间往往存在权衡。该项目将开发和展示一种大大改进的废气后处理方法，以减少NOx，特别是在低温燃烧状态下运行的发动机。具体的重点将是开发和测试一种新的系统，通过过热目前用于柴油发动机的柴油废气(DEF)来降低低成本的NOx。该项目不仅将开辟新的研究领域，还将直接影响发动机的燃烧和能源效率。NOx已经成为一个重要的问题，因为对燃油经济性的日益关注促使发动机消耗更少的燃料，从而在更低的温度条件下运行。这种低温操作导致了更冷的废气排放，开启和关闭发动机的混合动力系统只会加剧这个问题。此外，无法减少高水平的NOx，限制了柴油发动机的运行窗口。本项目将研究通过向发动机排气气流中喷射过热尿素来非平衡降低NOx。这一想法的核心是随着温度的升高，商用柴油废气(DEF)的NOx还原能力急剧上升，因为更高的化学反应速度。新系统在喷射前对尿素进行微波加热(至1200K)，使其更具反应性，实验证明，在商业锅炉中，在这种温度下，NOx的降低率高达96%。实验测试将被用来测量各种尿素注射情况下的废气成分，而计算机模拟将被用来提取与实验观察到的行为相对应的化学反应速率。该奖项反映了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。

Nitrogen oxide (NOx) is one of the major pollutants from diesel engines and has its own well-documented health and environmental impacts. Serious efforts have been devoted to reducing them through exhaust clean-up and combustion optimization. Interestingly, there are often trade-offs between efficiency and pollution. This project will develop and demonstrate a greatly improved exhaust after-treatment methodology for NOx reduction, particularly for engines operating at low-temperature combustion regimes. The specific focus will be on developing and testing a novel system for low-cost NOx reduction by super-heating the diesel exhaust fluid (DEF) currently used on diesel engines. The project will not only open up new areas of research, but also directly impact engine combustion and energy efficiency.NOx has become an important problem because the increased focus on fuel economy has driven engines to burn less fuel and consequently operate at a lower temperature condition. Such low-temperature operations have led to colder exhaust, with hybrid systems that turn the engine on and off only exacerbating this problem. Additionally, the inability to mitigate high levels of NOx has limited the operational window for diesel engines. This project will investigate non-equilibrium NOx reduction through injection of super-heated urea into an engine exhaust stream. Central to this idea is the steep rise of NOx reduction capacities of commercial diesel exhaust fluid (DEF), urea with water, with rising temperature because of higher chemical reaction rates. The new system uses microwave heating of the urea (to 1200 K) prior to injection to make it much more reactive, with experimentally proven NOx reduction of up to 96% for such temperatures in commercial boilers. Experimental testing will be used to measure the exhaust composition for various urea injection cases while computer modeling will be employed to extract the chemical reaction rates that correspond to experimentally observed behaviors.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.