Abstract
This paper evaluates the accuracy of the method used for emission measurement of gaseous pollutants, such as carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and carbon dioxide (CO2) from light-duty vehicles with spark-ignition (SI) and compression-ignition (CI) engines.
The main objective of the research was an identification of all possible uncertainty sources during exhaust emission measurement in order to eliminate them, or minimizing their influence on results and elaboration the method of the uncertainty estimating for emission tests on the chassis dynamometer. An uncertainty model using standard uncertainty propagation techniques has been used. The model, based on the individual uncertainty of the different equipment used in the measurement process, as well as the statistical analysis evaluated the uncertainties resulting from the errors introduced by the vehicle, the driver and the chassis dynamometer were used to compute the total uncertainty of the emission measurement.
The analysis showed that for the vehicle with compression-ignition engine fulfilled the Euro 3 emission standards the total uncertainty of emissions measurement can be expected about 26% for HC, 19,5% for NOx and about 15% for CO. For vehicles with spark-ignition engine that fulfilled Euro 3 the total uncertainty of emissions measurement can be expected 22,5% for NOx, 13% for HC and 11% for CO but for Euro 4 vehicles with SI engine it can reach even 53% for NOx, 39% for CO and 31% for HC.
The tests subject to analyses presented above have been performed in Exhaust Emission Laboratory of the BOSMAL Automotive Research and Development Centre in Bielsko-Biala, Poland within the research program evaluating the accuracy of the method used for measurement of the emission of gaseous pollutants from vehicles with spark-ignition (SI) and compression-ignition (CI) engines.
Keywords:accuracy, engine, exhaust emission measurement, uncertainty, vehicle