• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Wavelength-modulation spectroscopy for measurements of gas temperature and concentration in harsh environments.
【24h】

Wavelength-modulation spectroscopy for measurements of gas temperature and concentration in harsh environments.

机译：波长调制光谱仪用于在恶劣环境下测量气体温度和浓度。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

In this work, a practical implementation of calibration-free wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f) for measurements of gas temperature and concentration in harsh environments is presented. The method is applicable to measurements using lasers with synchronous wavelength and intensity modulation (such as injection-current-tuned diode lasers). The key factors that enable measurements without the on-site calibration normally associated with WMS are: (1) normalization of the 2f signal by the first-harmonic (1f) signal to account for laser intensity, and (2) the inclusion of laser-specific tuning characteristics in the spectral absorption model that is used to compare with measured 1f-normalized, WMS-2 f signals to infer gas properties. The uncertainties associated with the calibration-free WMS method are discussed, with particular emphasis on the influence of pressure and optical depth on the WMS signals. Many of these uncertainties are also applicable to calibrated WMS measurements.;The calibration-free WMS technique is applied to two harsh environments---internal combustion (IC) engines via a modified spark plug for measurements of temperature and H2O concentration, and a ground-test scramjet combustor during operation at Mach 5-equivalent flight speed for measurements of temperature, H2O, and CO2.;To develop the sensor for IC engine operation, careful laboratory measurements of direct-absorption and 2f spectra of H2O and CO2 at high pressure were performed to validate the spectral absorption models used to infer gas properties. The direct-absorption spectra confirm that the Lorentzian line shape model traditionally used for pressure-broadened absorption transitions is not sufficiently accurate to model spectra at high density (greater than a few amagat) due to the breakdown of the instantaneous collision assumption inherent to the Lorentzian model. Empirical corrections to the line shape model suggested by past researchers were found to reduce error in the spectral models; however, a well-validated model for non-Lorentzian effects on high-pressure CO2 and H2O absorption still does not exist that delivers the low uncertainty levels necessary for accurate gas property sensing. Alternatively, the 2f spectra are shown to be at least a factor of four less-influenced by these non-Lorentzian effects, eliminating the need in most cases for corrections to the 2f spectral absorption simulations.;The resulting WMS sensor for IC engines is capable of accurate, crank angle-resolved measurements of temperature and H2O concentration during the compression stroke of IC engines at a rate of 15 kHz. The temperature is determined from the ratio of absorption for two transitions of water vapor in the intake-gas mixture, and the H2O concentration is determined from this inferred temperature and the absorption for one of the transitions. The measurements sample a short-path region (6 mm) of the in-cylinder gases near the spark plug. The accuracy of the sensor was validated in a static cell, giving RMS errors of less than 3% in temperature and less than 3.6% in H2O concentration over a wide range of conditions. Measurements performed in unfired and fired engine cylinders illustrate the potential of this sensor for investigating a range of difficult-to-model trends in current and proposed IC engine combustion schemes.;The WMS sensor is extended for measurements of temperature, H2O, and CO2 in the harsh, supersonic flow of a scramjet combustor. A comparison of direct-absorption and WMS measurements shows a factor of 4 increase in signal-to-noise ratio with WMS for measurements of weakly-absorbing CO2 in the supersonic flow. Two-dimensional computational fluid-dynamics (CFD) calculations are compared with measurements of temperature and H 2O using a simple method that accounts for the influence of line-of-sight (LOS) non-uniformity on the absorption measurements. The comparisons show the ability of the LOS technique to gain useful information about multi-dimensional CFD models. In addition, fluctuations in temperature non-uniformity along the laser LOS are found to precede backpressure-induced unstart, a harmful condition which produces catastrophic failure to scramjets in flight. Though the precise cause of the fluctuations remains unknown, the detection method shows promise for use in control schemes to avoid back pressure-induced unstart in scramjets.;Overall, these demonstrations show that accurate, non-intrusive, high-bandwidth measurements can be made in harsh environments using the calibration-free WMS technique, and open the door to practical implementation of WMS in a variety of new environments that were previously too difficult for TDL absorption sensing. (Abstract shortened by UMI.)
机译：在这项工作中，提出了带有二次谐波检测（WMS-2f）的免校准波长调制光谱的实际实施方案，用于在恶劣环境中测量气体温度和浓度。该方法适用于使用具有同步波长和强度调制的激光器（例如注入电流调谐二极管激光器）进行的测量。无需进行通常与WMS关联的现场校准即可进行测量的关键因素是：（1）通过第一谐波（1f）信号对2f信号进行归一化以解决激光强度，以及（2）包含激光-光谱吸收模型中的特定调谐特性，用于与测得的1f归一化WMS-2 f信号进行比较，以推断气体性质。讨论了与免校准WMS方法相关的不确定性，尤其着重于压力和光学深度对WMS信号的影响。这些不确定性中的许多不确定性也适用于WMS校准测量;免校准WMS技术适用于两种恶劣环境-通过改进的火花塞用于测量温度和H2O浓度的内燃机（IC）发动机以及地面在5马赫当量飞行速度下对超燃冲压燃烧器进行测试，以测量温度，H2O和CO2 .;要开发用于IC发动机运行的传感器，请在高压下仔细实验室测量H2O和CO2的直接吸收光谱和2f光谱进行了验证以用于推断气体性质的光谱吸收模型。直接吸收光谱证实，由于洛伦兹固有的瞬时碰撞假设的分解，传统上用于压力扩展吸收跃迁的洛伦兹线形模型不足以准确地建模高密度（大于数个阿加马特）的光谱。模型。过去的研究人员建议对线形模型进行经验校正，以减少光谱模型中的误差。但是，仍然没有一个有效的模型来证明非洛伦兹效应对高压CO2和H2O的吸收，该模型提供了精确的气体特性检测所需的低不确定性水平。或者，显示2f光谱受这些非洛伦兹效应的影响至少减少了四分之一，从而在大多数情况下不需要校正2f光谱吸收模拟。;所得的用于IC引擎的WMS传感器能够在IC发动机压缩冲程期间以15 kHz的频率精确解析的曲柄角测量的温度和H2O浓度。根据进气混合物中水蒸气的两个跃迁的吸收比确定温度，并根据该推断的温度和其中一个跃迁的吸收率确定H2O浓度。这些测量对火花塞附近的缸内气体的短程区域（6毫米）进行采样。传感器的精度在静态电池中得到验证，在宽范围的条件下，RMS误差在温度范围内小于3％，在H2O浓度范围内小于3.6％。在未点火和点火发动机汽缸中进行的测量表明，该传感器具有潜力，可用于研究当前和拟议的IC发动机燃烧方案中一系列难以建模的趋势。WMS传感器已扩展为可测量发动机中的温度，H2O和CO2超燃冲压燃烧器的苛刻，超音速流动。对直接吸收和WMS测量的比较表明，对于超音速流中弱吸收CO2的测量，与WMS相比，信噪比提高了4倍。使用一种简单的方法将二维计算流体动力学（CFD）计算与温度和H 2O的测量进行比较，该方法考虑了视线（LOS）的不均匀性对吸收测量的影响。比较结果表明，LOS技术能够获得有关多维CFD模型的有用信息。另外，发现沿着激光视距的温度不均匀性波动先于反压引起的不启动，这是一种有害条件，会对飞行中的超燃冲压发动机造成灾难性故障。尽管尚不清楚波动的确切原因，但该检测方法显示出有望在控制方案中使用，从而避免超燃冲压发动机中反压引起的不启动。总的来说，这些演示表明可以进行准确，无干扰的高带宽测量使用免校准的WMS技术在恶劣的环境中工作，并为在以前对于TDL吸收传感来说太困难的各种新环境中实际实施WMS开辟了大门。 （摘要由UMI缩短。）

著录项

  • 作者

    Rieker, Gregory Brian.;

  • 作者单位

    Stanford University.;

  • 授予单位 Stanford University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 141 p.
  • 总页数 141
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号