Abstract
Keywords: Emissions, On-Board Measurement, Data Acquisition.
Abstract
Measurement of regulated pollutant emissions of light vehicles is carried out, on a grams per kilometre basis, on roller bench tests with a CVS sampling system. However, environmental impact studies require real traffic emission data. Also, for the validation of engine emission control technologies, it is convenient to carry out real driving measurements. Both aims lead to the need of real emissions measurements during the random conditions of urban traffic using on-board emission measuring equipments.
In the development of an on board measuring system, it is necessary to account for the capacity to withstand vibrations, shortage of electric energy and very little room. A common objective of this kind of studies is to determine real time tail-pipe emissions and to relate the emission mass flow to the instantaneous operating conditions of the engine and the vehicle. With this objective in mind, the Heat Engines Lab of the Universidad Politecnica de Madrid has undertaken the task of fitting two vehicles with equipments of two different technologies.
In one case, a small gasoline engine passenger car has been equipped with sensors to capture the operating conditions of the vehicle and a compact gas analyser capable of measuring CO2,
CO and HC with a NDIR system and O2 and NOx with electrochemical cells using dry sample techniques. The generated data are registered in a laptop computer via a RS232 line and a data acquisition card. In the other case, the vehicle is a big all-terrain with a diesel engine. The gas analysers measure HC with a FID and NOx with a chemiluminiscence sensor, both absorbing a wet and heated sample, and CO with a dry NDIR system. The opacity is measured via a partial flow opacimeter. The operating parameters of the vehicle are obtained directly from the ECU. The electric supply is provided by an on-board electric generator.
The objective of this study is to present both technologies, comparing their installation cost, the main problems encountered and the solutions proposed. Data from both equipments are supplied.