Modal pollutant emissions model of diesel and gasoline engines

Road traffic accounts for an important part of air pollution. For roughly 30 years, emission limits have been enforced by legislation in Europe and elsewhere. The success of the stringent regulations has been monitored by the environmental agencies. Althoughin the early days the interest was in the fulfillmcnt of the legislation limits, real-world emissions represent today's main focus. Emissions modcls are used to derive international, national and regional emis¬ sion inventories using measurementsperformedin emissions laboratories and to predict the impact of differenttraffic relatedmeasures. These emission mod¬ eis connect driving behaviour and fleet data to the emission measurementsfrom the test bench investigations. The availability of vehicle emission modeis has improved significantlyin the recent years. There are basically two types of emissions and fuel consumption modeis: one based on bag measurementsand the other based on instantaneous measurements. Emission modeis based on bag values give results for the traf¬ fic situations similar to the one used to fill the bag. If the driving behaviour changes, new measurementswith comparabledriving patterns have to be per¬ formed. To account for the additional effects as load, slope or gearshiftstrate¬ gies, bag based modeis include correction functions. However, these correction functions are based on a small numberof measurementswith few vehicles which may not be representative for the emissions behaviour. Moreover, the combination of these correction factors (i.e. when a vehicle drives uphill with a füll load) can be extremely misleading. Instantaneousemissions modelling maps the emissions at a given time to their generating "engine state", like vehicle speed, enginc speed, torque, etc. This makes it possible to integratenew, unmeasured driving patterns over the model and calculatetheir emission factorswithout furthermeasurements. Thus, emis¬ sion factors for a large numberof driving situationscan be determined from a small numberof measurements.