LDV and HDV vehicle exhaust emission indexes in PEMS-based RDE tests

摘要

In the applied models of total exhaust emissions from transport, the emission rate is adopted based on maximum admissible values prescribed in an exhaust emission homologation standard. In such a scenario, the results obtained from the models are only estimates, whose applicability may be restricted. It is thus necessary to seek new possibilities to assess vehicle exhaust emissions such as real-driving measurements. The measurements are performed under vehicle actual operating conditions and they use the PEMS (Portable Emission Measurement System) equipment. The research carried out at Poznan University of Technology with the use of this method attempts to answer questions regarding the exhaust emissions, their variability and relation to the engine and vehicle operating parameters. The paper presents several vehicles investigated for exhaust emissions under actual traffic conditions - RDE (Real Driving Emissions). The investigations led to developing exhaust emissions correction coefficients defined as a multiple of the increase or decrease of the exhaust emissions in operation compared to the homologation test. From the performed analysis it results that passenger gasoline vehicles meet the emission requirements and diesel vehicles significantly exceed the admissible emission of nitrogen oxides. This is also a characteristic feature of heavy-duty and non-road diesel vehicles. The paper draws attention to the emission of particulate matter in not only gasoline and diesel but also in CNG-fueled engines in terms of mass, number and size. It has been proved in the paper that the main problem of high-mileage vehicles is the increase in the mass of particulate matter not its number along with a significant surge in the level of gaseous exhaust components. The performed tests and determined values of the indexes allowed an evaluation of the environmental performance of vehicles of different emission categories. An interesting proposal for research, as presented in the paper, is the combination of a vehicle simulator with a dynamic engine test cell. Reproducing the vehicle run including the vehicle's motion resistance and translating it into the engine load allowed an assessment of the exhaust emissions under varied traffic conditions (traffic congestion, terrain elevation). The performed simulation tests were validated on real test objects fitted with the same engines. The performed investigations focused on a variety of road situations and their impact on the vehicle exhaust emissions.