The assessment of vehicle exhaust emissions referred to CO2 based on the investigations of city buses under actual conditions of operation

Abstract

The paper discusses the assessment of the exhaust emissions from heavy-duty vehicles following investigations under actual traffic conditions. The environmental characteristics presented thus far were mainly based on unit or road emissions. The paper presents an analysis of exhaust emissions referred to the harmful CO2, which was assumed as measure of correctness of the combustion process. The parameters determining this way are referred to as emission indexes. The research objects were 18-meter city buses fitted with three types of powertrains: conventional engine, hybrid (electric motor combined with a diesel engine) and a spark ignition engine fuelled with compressed natural gas (CNG). All buses were Euro V-EEV compliant. The measurements were performed according to the SORT 2 driving test procedure on the test route within the Poznan agglomeration. Investigations performed under actual traffic conditions allow a true assessment of environmental performance of a given research object because they cover a much greater engine operating parameter variability range compared to laboratory and homologation tests. The performed road tests and their analysis led to conclusions related to the applicability of the developed method of emission assessment based on emission indexes for vehicles fitted with different powertrains.