Abstract:

The negative impact of deteriorating air quality is receiving growing attention. As a result the contributing emission sources are increasingly regulated. Thus, the emissions of road transport, being one of the largest contributors, are under constant pressure. As such, the evolving legislation on emissions of new cars is forcing to low emission vehicles. To assist in the development and evaluation of those vehicles an on-board measuring system capable of determining emissions of carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC) and nitrogen oxides (NOx) is realised. This system ‘VOEMLow’ -VITO’s On-the-road Emission and energy Measurement system for Low emitting vehicles- combines the latest in laboratory grade analysers with a high speed condensing type sampling system in a state-of-the-art shock proof design. The regulated emission components can be detected to at least one ppm. The data-acquisition allows for the simultaneous retrieval of engine and vehicle parameters in order to calculate on-line mass based time resolved emissions that can be quickly linked to relevant parameters of the emission control system. The on-board system is validated by over 130 comparative simultaneous measurements on a Constant Volume Sampling (CVS) chassis dynamometer using modern light duty vehicles.

Particulate Matter (PM) emissions of diesel fuelled vehicles are of raising concern in most countries. To be able to compare emission laboratory results to real life data the on-board tailpipe emission monitoring system is enhanced with a module for dynamic mass PM emission measurements. The system is mounted in vehicles in such a way that the influence of on-road conditions such as shocks, vibrations and accelerations is minimal and allows the measurement of particulate filter equipped vehicles too. Validation experiments on a diesel car along different driving cycles have been performed by simultaneous CVS measurements on a chassis dynamometer. The integrated PM emission in g/km showed to be accurate to +/- 20%.

Real traffic measurements with VOEMLow have been performed on cars, vans, buses and garbage trucks, with various fuels (diesel, gasoline, biodiesel, CNG). The system has proved it can assess the newest vehicle technology in real world traffic and results confirm the progress that has been made in the development of clean vehicles.

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