Suitability Assessment of NOx Emissions Measurements with PTI Equipment

Suitability Assessment of NOx Emissions Measurements with PTI Equipment

Last 21 September has been published a study regarding the suitability of electrochemical gas analyzer equipment for NOx measurement at PTI.

The measurement of NOx emissions in vehicles has so far been exclusively carried out during the type-approval process. For this purpose, high-precision gas measurement laboratory equipment and Portable Emission Measurement Systems (PEMS) are used. Both types of equipment are costly in terms of price, maintenance, complexity, and time of use (calibration and maintenance requirements).

Currently, NOx emissions measurements in PTIs are being considered, but PEMS or laboratory equipment is unsuitable for this function, and PTI-grade equipment has to be used. Although CO and O2 are currently being reliably measured with this equipment, there is not enough information about its accuracy for NOx measurements.

Accordingly, in this paper, simultaneous measures have been performed over the same engine in a test cell, with a laboratory and a PTI gas analyzer to assess the accuracy of the latter. When performing the test with the most similar conditions found in PTI, the results show that the PTI gas analyzer shows an average deviation of 2.6 ppm and 9% rel. with respect to high-precision laboratory equipment for concentrations below 700 ppm NOx, which can be considered acceptable for periodic technical inspections.

Authors of the paper are Eugenio Fern├índez – University of Zaragoza, Abel Ortego and Alicia Valero – Research Centre for Energy Resources and Consumption (CIRCE), Universidad de Zaragoza, and Juan J. Alba – New Technologies in Vehicles and Road Safety (VEHIVIAL), Universidad de Zaragoza.

This paper was presented in the last CITA TA-D meeting on 8 September 2022.

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