| Zugriffsnummer | 32166 |
| Dokumenttyp | Konferenzartikel |
| Sprache | Englisch |
| Titel | Dual fiber-coupled laser hygrometer for fast in-situ gas analysis with minimized absorption path length |
| Autor(in); Institution |
Klein, Alexander; 3.2, Gasanalytik und Zustandsverhalten, PTB-Braunschweig
Ebert, Volker; 3.2, Gasanalytik und Zustandsverhalten, PTB-Braunschweig
|
| Quelle/Jahr | 58th IWK, Ilmenau Scientific Colloquium: Proceedings:(2014), 11 S. |
| Availability | [USB-Stick] |
| Herausgeber(in) |
Scharff, Peter
|
| Verlag | Ilmenau: Technische Universität |
| Konferenzangaben | Shaping the Future by Engineering ; 58th Internationales Wissenschaftliches Kolloquium der Technischen Universität Ilmenau ; 58th IWK, Ilmenau, Ilmenau, 08-12, September, 2014, Germany |
| Zusammenfassung | Direct tunable diode laser absorption spectroscopy (dTDLAS) offers the possibility for highly selective, fast, calibration-free and sensitive in-situ measurements of individual gas components. Minimally invasive fiber-coupled sensors are especially interesting for numerous applications e.g. process or combustion analysis, where compact sensors for applications with limited optical access are required. Especially the sensor development for the gas analysis in internal combustion engines is challenging as harsh environmental conditions and very confined space have to be considered. A new, very compact, high-speed diode laser hygrometer in the short-wave infrared with a fully fiber-coupled, minimally invasive sensor head was developed for highly localized absorption measurements in space confined applications like in engine diagnostics. The sensor optics has the dimensions of a typical engine spark plug, i.e. a small outer diameter of only 12 mm. To allow localized species measurements at the location of the ignition spark only a few millimeters absorption path are allowed for fast in-situ measurements of water vapor. To achieve a high sensitivity one major step in the spectrometer design is an application-specific absorption line selection in order to determine a target line with minimal spectral interference by other gas species, especially at higher pressures, optimized temperature dependence, as well as sufficient strong line strength. We isolated a well separated H2O absorption line in the fundamental rovibrational band around the 2.6 μm region. A major problem of this spectral region is the lack of industrial tested optical components and materials, so that the component selection and design has a major influence on the spectrometer performance. The design and development of the fiber-coupled dTDLAS hygrometer is discussed using customized IR optical components to realize a compact, minimally invasive dTDLAS sensor for harsh environments with a time resolution down to 100 μs. Laser, detector and electronic components are placed in one transceiver unit to be separated from the measurement point to reduce disturbances caused by vibrations as well as distortions of the results by ambient water vapour. A sensor prototype was fabricated and a validation of the spectroscopic, optical and mechanical concept was successfully conducted. An optical resolution of 3·10-3 absorbance was achieved. The sensor enables calibration-free H2O measurements at 10 kHz with a detection limit of 0.06 Vol.-% with a theoretical dynamic range from 0.1 Vol.-% up to 100 Vol.-% at pressures from 0.1 – 0.5 MPa. Further, the uncertainties for water vapor measurements using the dTDLAS were significantly improved by measuring the required molecular parameter (e.g. absorption linestrength of the rovibrational transition) with high accuracy. |
Zitierung
Klein, A. & Ebert, V. (2014). Dual fiber-coupled laser hygrometer for fast in-situ gas analysis with minimized absorption path length. Shaping the Future by Engineering ; 58th Internationales Wissenschaftliches Kolloquium der Technischen Universität Ilmenau ; 58th IWK, Ilmenau, Ilmenau, 08-12, September, 2014, Germany.