TDLAS-based NH mole fraction measurement for exhaust diagnostics during selective catalytic reduction using a fiber-coupled 2.2-µm DFB diode laser.
- Resource Type
- Article
- Authors
- Stritzke, Felix; Diemel, Oliver; Wagner, Steven
- Source
- Applied Physics B: Lasers & Optics. Apr2015, Vol. 119 Issue 1, p143-152. 10p. 1 Diagram, 2 Charts, 6 Graphs.
- Subject
- *SEMICONDUCTOR lasers
*SPECTROMETERS
*AMMONIA analysis
*WASTE gases
*ATMOSPHERIC carbon monoxide
- Language
- ISSN
- 0946-2171
A new developed tunable diode laser spectrometer for the measurement of ammonia (NH) mole fractions in exhaust gas matrices with strong CO and HO background at temperatures up to 800 K is presented. In situ diagnostics in harsh exhaust environments during SCR after treatment are enabled by the use of ammonia transitions in the ν + ν near-infrared band around 2300 nm. Therefore, three lines have been selected, coinciding near 2200.5 nm (4544.5 cm) with rather weak temperature dependency and minimal interference with CO and HO. A fiber-coupled 2.2-μm distributed feedback laser diode was used and attached to the hot gas flow utilizing adjustable gas tight high-temperature fiber ports. The spectrometer spans four coplanar optical channels across the measurement plane and simultaneously detects the direct absorption signal via a fiber-coupled detector unit. An exhaust simulation test rig was used to characterize the spectrometer's performance in ammonia-doped hot gas environments. We achieved a temporal resolution of 13 Hz and temperature-dependent precisions of NH mole fraction ranging from 50 to 70 ppm. There the spectrometer achieved normalized ammonia detection limits of 7-10 $${\text{ppm}}_{\text{V}}\cdot{\text{m}}$$ and 2-3 $${\text{ppm}}_{\text{V}}\cdot{\text{m}}/\sqrt{\text{Hz}}$$ . [ABSTRACT FROM AUTHOR]