Measurement and simulation of instantaneous emissions of a heavy truck diesel engine during transients

During the last decades, pollutant emissions from internal combustion engines used for transportation have become a major concern. Today, not only steady state emissions but also emissions during transients are regulated and have to be studied in order to be reduced In this paper we describe a new methodology developed to measure the instantaneous level of gaseous emissions from a internal combustion engine during transients, using an analyzer initially designed for steady state operation. Moreover a new phenomenological thermodynamical combustion model is proposed in order to compute emissions during transients. The results of these two methods are compared on various transients. The measurement method seems to give good results (except for hydrocarbon (HC) measurements), as long as the speed and load variations are not too fast. Otherwise, the frequency of the analyzer which was used becomes the limiting factor. The new combustion heat release developed to simulate transients, coupled with an existing two-zone model for emission calculations, leads to satisfactory results for CO2 and O-2 concentrations and NO, emissions. The agreement with measurements is good for smooth transients and seems promising for faster dynamics. The initial goal was reached, although some improvements are still necessary concerning HC measurements and the fastest transients. These results could be helpful when trying to reduce the amount of pollutant emissions at the exhaust during transients, directly or with after treatment devices.