New Directions in Ultrashort Pulse Laser Diagnostics: Towards Collision-Independent Multi-Species Detection and Imaging in Harsh Chemical Environments

最新的非侵入式光学和激光诊断方法为科学家和工程师设计下一代发动机、发电厂、推进系统、化学和等离子体处理设施等提供了巨大的机会。该研究项目的总体目标是开发新的物种测量技术，以表征恶劣环境下的基本物理和化学过程，例如现代燃气轮机燃烧室和IC发动机。这里开发的新技术有可能通过使用超短脉冲激光技术的最新发展，揭示反应流系统中定量、空间和时间分辨的关键中间物质测量。除了主要的研究成果外，研究生和本科生，包括少数民族和代表性不足的群体，还接受了独特的下一代激光基础和应用方面的培训。学生在多学科研究环境中工作，经常与外部研究团队互动，为他们在光学和能源相关技术领域的未来成功职业做好准备。研究成果将纳入正在进行的课程和课程开发工作，以及我们为K-12 STEM小组开展的外展活动，进一步增强这项工作的广泛影响。该项目的技术目标是开发一种基于超快激光的光学诊断技术，该技术能够在恶劣的环境中测量化学物质，最初的重点是高度反应的原子物质，而不考虑限制此类测量精度和准确性的复杂淬火过程。在这样的湍流流场中，猝灭伙伴的时空变化浓度几乎是不可能量化的。此外，校正所需的温度和压力相关的物种特异性淬火截面数据相当有限，在许多实际情况下几乎不可能获得。近年来，基于飞秒激光的诊断工具在火焰和等离子体中的原子和分子物种的高重复率成像方面取得了重大进展。然而，分子猝灭效应在这些诊断中仍然盛行。在目前的工作中，研究了创新的非线性光学技术，通过测量重要的原子和分子物种而不需要淬火校正，将这种诊断提升到一个新的水平。新的诊断方法将在高压条件下以及复杂的反应湍流条件下进行评估。随后，它们将用于生成关键数据集，用于在一组选定的湍流火焰中验证化学动力学模型，并表征为化学动力学研究设计的新型“无壁”反应器。

1604633 - KulatilakaState-of-the-art, nonintrusive optical and laser-based diagnostic methods can unveil tremendous opportunities for scientists and engineers designing next generation engines, power plants, propulsion systems, chemical and plasma processing facilities, among many others. The overarching goal of this research project is to develop novel species measurement technique to characterize fundamental physical and chemical processes in harsh environments such as those present in modern gas turbine combustor and IC engines. The new techniques developed here have the potential to uncover quantitative, spatially and temporally resolved key intermediate species measurements in reacting flow systems by using the latest developments in the ultrashort pulse laser technology. In addition to primary research outcomes, graduate and undergraduate students including minorities and underrepresented groups are trained in unique, next-generation laser fundamentals and applications. Students work in multidisciplinary research environments and often interact with outside research teams, preparing them for successful future careers in optics and energy related technologies. Research findings will be incorporated into ongoing curriculum and course development work as well as our outreach activities for K-12 STEM groups, further enhancing the broader impacts of this effort. The technical objective of this project is to develop an ultrafast-laser-based optical diagnostic technique capable of measuring chemical species-with initial focus on highly reactive atomic species-in harsh environments without taking in to account complex quenching processes that limit the precision and accuracy of such measurements. Space and time varying concentrations of quenching partners are virtually impossible to quantify in such turbulent flow fields. Furthermore, temperature- and pressure-dependent species-specific quenching cross section data needed for corrections are rather limited and virtually impossible to obtain in many practical situations. In recent years, significant advances have been made in femtosecond-laser-based diagnostic tools for high-repetition-rate imaging of atomic and molecular species in flames and plasmas. However, molecular quenching effects have still prevailed in these diagnostics. In the present work, innovative new nonlinear optical techniques are investigated to elevate such diagnostics to the next level by measuring important atomic and molecular species without the need of quenching corrections. The new diagnostics will be evaluated in high-pressure conditions as well and complex reacting turbulent flow conditions. Subsequently, they will be used to generate critical data sets for chemical kinetics model validation in a selected set of turbulent flames and to characterize a new type of 'wall-less' reactor designed for chemical kinetics studies.