Impact of driving dynamics in RDE test on NOx emissions dispersion

Abstract

[EN] EU6D emission regulation intends to bridge the gap between laboratory tests and the real driving conditions by introducing real drive emission testing. It requires the measurement of real drive emission to be an additional type approval test in order to take into account the influence of road profile, ambient conditions and traffic situations. An important amendment has been included in Commission regulation (European Union) 2016/646, limiting the driving dynamics and hence avoiding the biased testing of the vehicle. In this work, a drive cycle generator has been developed to synthesise cycles meeting all the regulatory requirements of the real drive emission testing. The generator is based on the transition probability matrix obtained from each phase of the World harmonised Light vehicle Test Procedure cycle. Driving dynamics have been varied based on real drive emission regulations, and several trips have been generated with dynamics ranging from soft to aggressive. A direct injection compression ignition 1.5 L engine with a state-of-the-art aftertreatment system has been utilised to run the generated synthetic cycles. The analysis of the results obtained in the tests (all of them complying with real drive emission restrictions in terms of driving dynamics) points out a noticeable 60% relative dispersion in the NO(x)emissions downstream of the catalyst. The contribution of the proposed method lies not only in the fact that it synthesises driving cycles as stochastic process and is capable of tuning the driving dynamics based on real drive emission regulations, but it also presents the range of dispersion possible in NO (x)emissions solely due to the driving dynamics. The methodology followed in the present work could be an essential step in future engine developments, where testing engine prototypes on the entire range of driving dynamics in the engine test bench facility could provide interesting insights about the expected NO(x)emissions in real drive emission testing.