Femtosecond Coherent Anti-Stokes Raman Scattering for Time-Resolved Measurements of Temperature and Species Concentrations in Flames

项目摘要：飞秒相干反斯托克斯拉曼散射用于火焰温度和组分浓度的时间分辨测量。拉斐特，IN 47907- 2088拟议工作的主要目标是开发和应用基于超快激光的相干反斯托克斯拉曼散射（汽车）技术，以1 kHz或更高的数据速率进行温度和物质浓度的单次测量。 从湍流介质中获取完全时间分辨的数据将提供更严格和有意义的湍流火焰模型测试，最终导致燃烧室更有效，污染物排放水平更低。 在实际燃烧室的试验过程中，特别是当试验持续时间受到设备考虑的限制时，1 kHz的测量数据率将是一个很大的优势。 这项工作代表了为能源和环境应用提供飞秒汽车传感器的第一步。 该研究将为机械工程专业的研究生提供良好的培训。 飞秒（fsec）汽车项目将为机械工程研究生提供多学科活动的机会，因为fsec激光系统的操作需要相当多的光学物理和电子专业知识。 fsec雷射系统与fsec雷射物理学之课程将并入高级雷射诊断学之研究生课程。 来自代表性不足群体的学生将积极招募这项研究，在本科和研究生水平。 为了协助本科生和研究生的招聘，将创建一个fsec汽车项目网站。 飞秒汽车测量将使用普渡大学现有的激光设备进行;标称脉冲长度为80 fsec的780 nm激光脉冲可以在1 kHz的重复率下产生超过1 mJ的脉冲能量。 泵浦和探测脉冲将使用光学参量放大器产生。 为了以1 kHz或更高的数据速率测量温度和/或物质浓度，将使用脉冲长度为2-3皮秒的啁啾脉冲探测光束将拉曼相干性的时间行为映射到汽车信号的频谱上。 汽车信号将使用光谱仪进行分散，并使用背照式电子倍增CCD（EMCCD）进行检测。 这EMCCD相机已被开发为帧传输相机和汽车光谱可以在1 kHz或更高的数据速率提取。 独特的数值方法计算的fsec汽车信号产生过程将被用来探索的fsec汽车过程的物理，包括泵浦和斯托克斯光束的相互作用的细节，以创建的拉曼相干性，并开发计算机代码，用于确定温度和物种浓度从实验数据。

PROJECT ABSTRACT: Femtosecond Coherent Anti-Stokes Raman Scattering for Time-Resolved Measurements of Temperature and Species Concentration in FlamesRobert P. Lucht and Xianfan Xu School of Mechanical Engineering, Purdue University, W. Lafayette, IN 47907-2088The primary objective of the proposed work is the development and application of ultrafast-laser-based coherent anti-Stokes Raman scattering (CARS) techniques for single-shot measurements of temperature and species concentrations at data rates of 1 kHz or greater. The acquisition of fully time-resolved data from turbulent media will provide more rigorous and meaningful tests of turbulent flame models, leading eventually to combustors that are more efficient and have lower levels of pollutant emission. The 1-kHz data rate of the measurements will be a great advantage during testing of practical combustors, especially when the test duration is limited by facility considerations. The work represents a first step toward enabling femtosecond CARS based sensors for energy and environment applications. The proposed research will provide excellent training for graduate students in mechanical engineering. The femtosecond (fsec) CARS project will provide numerous opportunities for multidisciplinary activities for mechanical engineering graduate students, because operation of the fsec laser systems requires considerable expertise in optical physics and electronics. The subjects of fsec laser systems and fsec laser physics will be incorporated in a graduate class on advanced laser diagnostics. Students from underrepresented groups will be actively recruited for this research, at both the undergraduate and graduate levels. To assist in undergraduate and graduate recruitment, a fsec CARS project web site will be created. The femtosecond CARS measurements will be performed using an existing laser facility at Purdue University; laser pulses at 780 nm with a nominal pulse length of 80 fsec can be generated with pulse energies in excess of 1 mJ at a repetition rate of 1 kHz. Pump and probe pulses will be produced using an optical parametric amplifier. To measure temperature and/or species concentrations at data rates of 1 kHz or greater, a chirped-pulse probe beam with a pulse length of 2-3 psec will be used to map the temporal behavior of the Raman coherence onto the frequency spectrum of the CARS signal. The CARS signal will be dispersed using a spectrometer and detected using a back-illuminated electron multiplying CCD (EMCCD). This EMCCD camera has been developed as a frame transfer camera and CARS spectra can be extracted at data rates of 1 kHz or greater. Unique numerical methods for calculation of the fsec CARS signal generation process will be used to both explore the physics of the fsec CARS process, including the details of the interaction of the pump and Stokes beams to create the Raman coherence, and to develop computer codes for determination of temperatures and species concentrations from experimental data.