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

建议编号：CTS 9977481首席研究员：N·克莱门斯这项主要研究仪器(MRI)奖支持自发拉曼散射仪器的开发。自发振动拉曼散射已被证明是燃烧研究中最重要的诊断技术之一，因为它能够同时提供关于几种物质浓度的空间分辨信息。然而，传统的拉曼散射系统使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频率(通常为5到几百赫兹)的限制。低采样率的问题是测量仅限于基本随机的采样，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，能够以10 kHz或更高的速率在湍流火焰中基本上连续地单点测量所有主要物质(因此混合物的分数)和温度。这项工作的一个核心要素将是开发一种工作在可见光波长下的高重复频率激光系统。为了实现这一目标，Proposal将与工业界的合作伙伴合作开发一种满足拟议仪器的苛刻要求的激光器。被提议的激光器将是一个二极管泵浦的Nd：YAG激光器，它将被倍频到可见(绿色)波长。它的平均功率为150瓦，重复频率为10千赫或更高；这样的激光器将是商业开发的第一个此类激光器。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是很高(在10千赫时为15毫焦耳)，因此需要付出大量努力才能最大限度地提高所收集的光。这将通过利用多通道电池来实现，从而使探头体积中的激光能量增加一个数量级。该系统将采用单独的定制设计的快速收集光学元件和高效干涉滤光片。该系统将为大气压湍流甲烷火焰中的所有主要物种提供出色的单次信噪比。

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.