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A NOx Sensor for Feedback Control and Emissions Reduction
Technical Paper
2002-01-0479
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Current emission control systems utilize a catalytic converter employing a three-way catalyst (TWC), composed of a mixture of noble metals to minimize the three main pollutant classes of NOx, CO, and HC. The TWC is most efficient when the air-to-fuel ratio (A/F) is at stoichiometry (i.e. A/F ≈ 14.7). The stoichiometric set-point region is maintained by the use of oxygen sensors composed of the solid-electrolyte yttria stabilized zirconia (YSZ) in an electronic feedback loop. As combustion gets leaner a different exhaust sensor can be utilized to give a measure of the level of pollutants. A NOx sensor is an alternative for an oxygen sensor that can be used for feedback control of engine combustion or exhaust NOx traps. A solid electrolyte disk composed of YSZ having two Pt electrodes with one being covered by a microporous zeolite material was tested as a sensor for combustion produced gases such as NO and NO2 in the presence of O2. At 500°C it was found that the sensor responded to the NOx gases and was hardly affected by changing O2 levels in the range of 1-10%. A modified sensor design was used in a prototype assembly constructed to allow in-situ testing in an I-4 automobile engine when the engine cycle was perturbed. The sensor showed a response with changing gas concentrations and was correlated with an on-line FTIR gas analyzer. The sensor assembly design may show promise for catalytic converter monitoring or engine control diagnostics.
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Szabo, N., Dutta, P., and Soliman, A., "A NOx Sensor for Feedback Control and Emissions Reduction," SAE Technical Paper 2002-01-0479, 2002, https://doi.org/10.4271/2002-01-0479.Also In
Electronic Engine Controls 2002: Electronics and Information Gathering
Number: SP-1690; Published: 2002-03-04
Number: SP-1690; Published: 2002-03-04
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