Zusammensetzung der Kohlenwasserstoffe im Abgas unterschiedlicher Fahrzeugkonzepte

In this study the exhaust gas of cars equipped with different engine types, i.e. cars with diesel engines, cars with petrol engines and three-way-catalysts, and cars with petrol engines without catalysts was analysed. Five cars of each engine type were measured on a chassis dynamometer under conditions of the US-75 test procedure and the 'Autobahn' test. The emission factors of CO, NO_x, total HC, particles and CO_2 were determined. In addition, measurements of 45 different hydrocarbons, 9 different carbonyles, phenole and the sum of the cresoles were performed. The influence of the cold start phase and the mean velocity on the composition of the car exhaust was analysed with special emphasis on the individual VOC's (VOC-split). For this purpose, the different phases of the test cycles were regarded separately. The cars equipped with a three-way-catalyst showed the largest span of the emission factors in grams per kilometre over the different test phases. The highest emissions of hydrocarbons and carbonyles were observed during the cold start (first phase of the US-75 test) when the catalyst is not or not fully active. Compared to the cold start the emissions are reduced by a factor of 10 to 20 in the other phases of the US-75 test. On the other hand with higher mean velocities as driven in the 'Autobahn' test an increase of the emissions nearly up to the level of the cold start emissions was observed. This effect is due to the change of the air-fuel-ratio. When high loads are needed, more fuel is added and therefore the conversion efficiency of the catalyst is decreasing. The VOC split was analysed by grouping the individual VOC into five different substance classes: alkanes, alkenes, aromatics, carbonyles and phenoles. For cars with three-way-catalysts large changes in the VOC split were observed for the different test phases. In the cold-start phase the contribution of aromatic compounds was largest, followed by alkenes and alkanes. In the warm phases of the US-75 alkanes are the most prominent substance class. In the Autobahn test the contribution of the aromatics increases with increasing mean velocity. (orig.)Available from TIB Hannover: RA 831(3646) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman