MRI: Development of a High Repetition Rate Raman Scattering Instrument for Combustion Research

MRI：开发用于燃烧研究的高重复率拉曼散射仪器

• 批准号: 9977481
• 负责人: Noel Clemens
• 金额: $ 43.79万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9977481&HistoricalAwards=false
• 关键词: MRI; Development; Repetition; Rate; Raman

Proposal Number: CTS 9977481Principal Investigator: N. ClemensThis Major Research Instrumentation (MRI) award supports the development of a spontaneous Raman scattering instrument. Spontaneous vibrational Raman scattering has proven to be one of the most important diagnostic techniques in combustion research owing to its ability to provide spatially resolved information on the concentration of several species simultaneously. However, conventional Raman scattering systems employ high-power pulsed lasers where the rate at which they can acquire data is limited by the pulse repetition rate (typically 5 to few hundred Hz). The problem with low sampling rates is that they restrict measurements to essentially random sampling, so that statistical information can be extracted, but important time-correlation information cannot be captured.It is proposed to develop a spontaneous Raman scattering instrument that will enable essentially continuous single-point measurements of all major species (hence mixture fraction) and temperature simultaneously in a turbulent flame, at a rate of 10 kHz or more. A core element of this effort will be the development of a high-repetition rate laser system that operates at visible wavelengths. In order to accomplish this, the proposes will work with a partner in industry to develop a laser that meets the demanding requirements for the proposed instrument. The proposed laser will be a diode-pumped Nd:YAG laser that will be frequency doubled to a visible (green) wavelength. It will operate at an average power of 150 W in the green with a repetition rate of 10 kHz and above; such a laser would be the first of its kind developed commercially. Once the laser is delivered, substantial work will be required to develop an instrument that can be used to make meaningful measurements in actual large-scale laboratory flames. Despite the fact that the average power of the laser is quite high, the energy per pulse is not (15 mJ at 10 kHz), and thus substantial effort will be required to maximize the light collected. This will be accomplished by utilizing a multi-pass cell so that the laser energy in the probe volume is increased by an order-of-magnitude. The system will employ separate custom-designed fast collection optics and high efficiency interference filters. This system will yield excellent signal-to-noise ratios on a single-shot basis, for all major species in an atmospheric pressure turbulent methane flame.

该主要研究仪器（MRI）奖支持自发拉曼散射仪器的开发。自发振动拉曼散射由于能够同时提供几种物质浓度的空间分辨信息，已被证明是燃烧研究中最重要的诊断技术之一。然而，传统的拉曼散射系统采用高功率脉冲激光器，其获取数据的速率受到脉冲重复率的限制（通常为5到几百赫兹）。低采样率的问题在于，它们将测量限制为基本上是随机采样，因此可以提取统计信息，但无法捕获重要的时间相关信息。建议开发一种自发拉曼散射仪器，该仪器将能够在湍流火焰中同时以10 kHz或更高的速率连续测量所有主要物质（因此混合物分数）和温度。这项工作的核心要素将是开发一种在可见波长下工作的高重复频率激光系统。为了实现这一目标，提议将与工业界的合作伙伴合作，开发一种满足提议仪器要求的激光器。提出的激光器将是二极管泵浦Nd:YAG激光器，其频率将加倍到可见（绿色）波长。绿色区域的平均功率为150w，重复频率为10khz及以上；这种激光器将是第一个商业化开发的激光器。一旦激光被发射，将需要大量的工作来开发一种仪器，可以用于在实际的大规模实验室火焰中进行有意义的测量。尽管激光的平均功率相当高，但每脉冲的能量不是（10千赫时15兆焦耳），因此需要大量的努力来最大限度地收集光。这将通过利用多通道单元来实现，从而使探头体积中的激光能量增加一个数量级。该系统将采用单独定制设计的快速采集光学器件和高效干涉滤光片。该系统将在单次射击的基础上产生优异的信噪比，适用于大气压湍流甲烷火焰中的所有主要物种。