Werblinski Thomas, Kleindienst Stefan, Engelbrecht Rainer, Zigan Lars, Will Stefan
Appl Opt. 2016 Jun 10;55(17):4564-74. doi: 10.1364/AO.55.004564.
A broadband supercontinuum (SC) based absorption spectrometer capable of cycle-resolved multiparameter measurements at internal combustion (IC) engine conditions is presented. Three parameters, temperature, pressure and water mole fraction, were extracted from broadband near-infrared HO absorption spectra, spanning the wavelength-range from 1340 to 1405.5 nm, which exhibits a large number of specific HO transitions. The spectrometer is based on spatial domain detection and features a near-infrared line scan camera as a detector. Measurements were performed during a compression cycle of a rapid compression machine comprising a pressure and temperature range from 2.5 to 65 bar and 300 to 900 K, respectively. With the new spectrometer, we are for the first time, based on the authors' knowledge, able to perform measurements based on SC radiation over a complete compression and expansion stroke at measurement rates up to 50 kHz. A detailed overview is provided about the best match algorithm between theory and experiments, including parameters from two different spectral databases, namely the Barber-Tennyson database (BT2) and HITRAN2012. The results indicate that spectral broadening effects are not properly described by theory, especially at pressure levels exceeding 20 bar, which culminates in a clear underestimation of the derived pressure data by SC absorption spectroscopy. Nevertheless, temperature can be determined accurately by performing a three-parameter fit based on water mole fraction, temperature, and pressure. In contrast, making use of pressure transducer data as look-up values and varying only temperature and HO mole fraction to find the best match leads to a clear overestimation of temperature at elevated pressures.
本文介绍了一种基于宽带超连续谱（SC）的吸收光谱仪，它能够在内燃机工况下进行循环分辨多参数测量。从波长范围为1340至1405.5 nm的宽带近红外HO吸收光谱中提取了温度、压力和水摩尔分数这三个参数，该光谱展现出大量特定的HO跃迁。该光谱仪基于空间域检测，以近红外线扫描相机作为探测器。测量是在一台快速压缩机的压缩循环过程中进行的，压力范围为2.5至65 bar，温度范围为300至900 K。据作者所知，借助这台新型光谱仪，我们首次能够基于SC辐射在整个压缩和膨胀冲程以高达50 kHz的测量速率进行测量。文中详细概述了理论与实验之间的最佳匹配算法，包括来自两个不同光谱数据库的参数，即巴伯 - 坦尼森数据库（BT2）和HITRAN2012。结果表明，理论并未恰当描述光谱展宽效应，尤其是在压力超过20 bar时，这最终导致通过SC吸收光谱法得出的压力数据明显被低估。然而，通过基于水摩尔分数、温度和压力进行三参数拟合，可以准确测定温度。相比之下，将压力传感器数据用作查找值，仅改变温度和HO摩尔分数来寻找最佳匹配，会导致在高压下温度明显被高估。
