Particulate emissions of diesel fuelled vehicles are of rising concern in most countries. To be able to compare emission lab results to real life data the on-board tailpipe emission monitoring system 'VOEM' - VITO's On-road Emission and energy Measurement system - is enhanced with a module for dynamic mass PM emission measurements. The new part consists of a R&P TEOM 1105 measuring device coupled with a Horiba MDT-905 sampling system. The TEOM is mounted in vehicles in such a way that the influence of on-road conditions such as shocks, vibrations and accelerations is minimal i.e. below 2mg/cu m. The MDT is a portable version of Horiba's Micro Dilution Tunnel. The system is computer controlled over a mil spec laptop PC. Validation experiments on diesel cars along different driving cycles have been performed by simultaneous CVS-VOEM measurements on a chassis dynamometer. The integrated PM emission in g/km showed to be accurate to +/-20%. First measurements are performed on a EURO-2 diesel city bus. On a circuit a city cycle is driven in both power and economy gear box mode. The CO-, THC-, NOx- and PM emissions in power mode are respectively 5, 1.3, 20 and 0.5 g/km. In economy mode the figures are respectively 6, 1.0, 19 and 0.9 g/km. Although the bus is more energy efficient by 10% in this last mode the emissions overall tend to increase. The PM emission increases most by far. Detailed analysis of the on line data shows this to be due to the engine operating in low lambda conditions for longer periods. (A)
Abstract