Uncertainty in real-world particulate matter emission measurements from a transportable heavy-duty vehicle emissions testing laboratory
by Mridul Gautam, Eric S. Miller, Donald H. Ferguson, Donald W. Lyons
International Journal of Heavy Vehicle Systems (IJHVS), Vol. 5, No. 3/4, 1998

Abstract: In recent years, significant improvements have been made in the measurement and characterisation of in-use emissions from heavy-duty vehicles. The recent efforts to measure in-use (real-world) emissions has been underscored by the need to improve the models used to generate mobile source emission inventories. The emissions data generated by the West Virginia University Transportable Heavy-Duty Vehicle Emission Testing Laboratories is filling the void in the database. The increasingly stringent standards on exhaust emissions necessitate a higher degree of accuracy and repeatability in the measurements. This paper will present an analysis of the uncertainty of the inaccuracy associated with in-use particulate matter measurements using the transportable laboratory. It was found that the error in the HC, CO, CO₂, and NO_x, measurements were dependent upon the bias and random errors inherent with each of the analysers. While the emission measurements of particulate matter were affected by the error in the analysers, a sensitivity analysis revealed that the largest contributor to the uncertainty in this measurement was the dilute exhaust mass flow rate, V_mix. The uncertainty in the particulate matter emission measurement was found to be less than 2%. It was found that the error in the particulate measurement was directly proportional to the error in the V_mix. When the error in the V_mix was 1% the error in the particulate measurement was approximately 1%. The errors associated with the pressure transducer, which measured the absolute pressure at the critical flow venturi inlet, and the critical flow venture constant, Κ, also contributed significantly to the uncertainty.

Online publication date: Tue, 18-Jun-2013

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