Changing of emission levels leads to an increasing demand for a satisfying solution to measure mass emissions of motor vehicles on both, engine and chassis dynamometers. Partial flow systems may fit to the demands. These systems require an exact determination of exhaust volume flow and time aligned concentration measurement. This paper will address these issues and problems related with partial flow sampling. Several exhaust flow measurement systems have been studied and integrated mass results have been checked against the full flow CVS. As the investigations indicate, modal mass calculation from sampling direct exhaust at the end of tailpipe is feasible but not a satisfying solution in equivalency and repeatability in comparison to CVS-results. This is especially the case on emission levels near or below ULEV. Calibrating an engine to low emission levels has become one of the most difficult tasks in vehicle development. This creates a demand for the measurement of mass emissions already at engine test beds. That is the reason why there is a need for small, reliable, and accurate measuring equipment. A promising way is to measure time resolved tailpipe concentrations and combine them with the corresponding direct vehicle exhaust volume. Hence some important aspects of this method have been examined. Of the studied devices ultrasonic device No. 3 yielded the best results. At small volume flows none of the studied systems could completely satisfy the demands. Deviation to CVS bag results larger +/- 5 % for CO2 have to be expected. High sampling rates for volume and emission measurement systems are desirable. A proper calibration and verification tool for exhaust flow meters under transient conditions (temperature, gas composition including moisture) is necessary. The tested partial sampling systems with a proper application can be perfectly acceptable for engine development on engine test rigs. However, raw modal mass integration is not reliable enough to substitute CVS measurement technology. Especially for certification, confirmatory or compliance testing on chassis dynamometer enhanced CVS remains the system of choice.


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    Title :

    Problems of partial sample systems for modal raw exhaust mass emission measurement


    Additional title:

    Probleme bei partiellen Probeentnahmesystemen zur Messung der Abgasmenge bei ungeschulter Verfahrensweise


    Contributors:
    Thiel, W. (author) / Hornreich, C. (author) / Mörsch, O. (author) / Seifert, G.E. (author)


    Publication date :

    2003


    Size :

    13 Seiten, 18 Bilder, 2 Tabellen, 16 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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