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

提案编号：CTS 9977481主要研究者：N.克莱门斯这个主要的研究仪器（MRI）奖支持自发拉曼散射仪器的发展。由于自发振动拉曼散射能够同时提供几种物质浓度的空间分辨信息，因此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，其中它们可以获取数据的速率受到脉冲重复率（通常为5到几百Hz）的限制。低采样率的问题是，它们将测量限制为基本上随机的采样，因此可以提取统计信息，但是不能捕获重要的时间相关信息。建议开发一种自发的拉曼散射仪器，其将能够基本上连续地对所有主要物种进行单点测量（因此混合物分数）和温度同时在湍流火焰中，在10 kHz或更高的速率。这项工作的核心内容将是开发一种在可见光波长下工作的高重复频率激光系统。为了实现这一目标，建议将与工业合作伙伴合作，开发一种激光器，以满足拟议仪器的苛刻要求。拟议的激光器将是一个二极管泵浦的Nd：YAG激光器，将倍频到可见光（绿色）波长。它将以150瓦的平均功率在绿色中工作，重复频率为10千赫以上;这种激光器将是商业上开发的第一种此类激光器。一旦激光被交付，将需要大量的工作来开发一种仪器，可以用来在实际的大规模实验室火焰中进行有意义的测量。尽管激光器的平均功率相当高，但每个脉冲的能量不高（在10 kHz时为15 mJ），因此需要大量的努力来最大化收集的光。这将通过利用多程单元来实现，使得探针体积中的激光能量增加一个数量级。该系统将采用单独的定制设计的快速收集光学器件和高效干涉滤光片。该系统将产生良好的信号-噪声比在一个单一的拍摄的基础上，为所有主要物种在大气压湍流甲烷火焰。

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.