Time-resolved exhaust gas analysis by infrared diode laser spectroscopy

We report on a fast exhaust gas analysis system, based on infrared spectroscopy of a singel 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 single strokes and dynamic engine operation changes. Results are shown to depend on the sampling position, which was varied from close to the outlet valve to behind the catalyst. A comparison with conventional techniques yields good overall agreement for stationary engine operation.