Dynamische Abgasmessung mit Diodenlasern.

Abstract

We report on a fast exhaust gas analysis system, based on infrared spectroscopy of a single absorption line by pulse-operated diode lasers and a newly designed gas sampling system. Otto and Diesel engines in dynamic test beds were investigated. A rise time smaller than 3 ms and detection limits of 100 ppm for NO and 20 ppm for CO were obtained with resolution of dynamic engine operation changes. For time resolution of a single stroke the exhaust gas sample point should be close to the exhaust valve. Unexpected fast variations in NO and CO content were observed even behind the catalyst with regular engines under stationary conditions. Concentration changes occuring faster than 100 ms were detected and are attributed to oscillations of the engine control system. First applications of the system have shown it to be important for the analysis and optimization of modern engines