Multi-parameter determination in practical combustion systems by broadband high-speed absorption spectroscopy

本项目旨在开发和应用一种新型灵敏的高速吸收测量系统，用于全面表征燃烧过程。计划中的系统首次允许在较宽的温度和压力范围内同时高速检测温度(通过H2O吸收管路)和重要的燃烧中间体(H_2O_2、C_2H_2)以及主要燃烧产物(H_2O、CO、CO)。主要部件是超连续谱光源和高速近红外线相机。该新型光源克服了以前基于吸收的概念的有限光谱带宽。线路探测器用作高分辨率、模块化光谱仪中的传感器，允许高达10 kHz的采集率。由于超连续谱光源的高光谱功率密度，该装置进一步方便了光学腔的实现，在不降低探测率的情况下扩展测量体积内的光束路径。这里，特别关注线探测器的线性度的控制以及分辨率的确定，即光谱仪的仪器功能。此外，腔内附加的部分反射表面相对于有效光束路径的影响将被量化。随后，将在标定测量的基础上开发一种评估算法，并将该测量系统应用于一维平焰燃烧器。最后，在内燃机条件下，在快速压气机(RCM)上完成了多参数的确定。在RCM中，研究了不同代用燃料在不同废气含量和压缩比下的两级燃烧特性。点火前和点火过程中的温度轨迹以及第一阶段燃烧的持续时间和最高温度峰值是进一步发展现代燃烧概念(如低温燃烧)的重要参数。新开发的测量系统将在项目第二阶段应用于可光学访问的研究发动机。然后，还将把重点放在构建适用于测量发动机循环分辨2D温度场的层析传感器上。

This project aims at the development and application of a novel sensitive high-speed absorption based measurement system for a comprehensive characterization of combustion processes. For the first time, the planned system allows for the simultaneous high-speed detection of temperature (via H2O-absorption lines) and important combustion intermediates (H2O2, C2H2) as well as main combustion products (H2O, CO2, CO) in a wide temperature and pressure range. Main parts are a supercontinuum light source and a high-speed near-infrared line-camera. The novel light source overcomes the limited spectral bandwidth of previous absorption based concepts. The line-detector is used as sensor in a highly resolving, modular spectrograph and allows for acquisition rates of up to 10 kHz. Because of the high spectral power density of the supercontinuum light source, the setup further facilitates the implementation of an optical cavity to extend the beam path within the measurement volume without a reduction of the detection rates.In the first phase of the project the measurement system will be built up and fundamentally characterized. Here, special focus is laid on the control of the linearity of the line detector as well as on the determination of the resolution, i.e. the instrumental function of the spectrograph. Further, the influence of additional partially reflective surfaces within the cavity with respect to the effective beam path will be quantified. Subsequently, an evaluation algorithm will be developed, based on calibration measurements, and the measurement system will be applied to a 1D-flat flame burner. Finally multi-parameter determination will be accomplished in a rapid compression machine (RCM) under IC engine conditions. In the RCM two-stage combustion characteristics of different surrogate fuels will be investigated under varied exhaust gas content and compression ratio. The temperature trace prior to and within the ignition process as well as the duration of the first phase combustion and the maximum temperature peak are important parameters for the further development of modern combustion concepts such as low temperature combustion (LTC).The newly developed measurement system will be applied to an optically accessible research engine in the second phase of the project. Additional focus will then be laid on the construction of a tomographic sensor applicable to measure cycle-resolved 2D-temperature fields in engines.