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Journal of Sensors and Sensor Systems An open-access peer-reviewed journal
J. Sens. Sens. Syst., 7, 79-84, 2018
https://doi.org/10.5194/jsss-7-79-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Regular research article
16 Feb 2018
A pathway to eliminate the gas flow dependency of a hydrocarbon sensor for automotive exhaust applications
Gunter Hagen, Antonia Harsch, and Ralf Moos Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95440 Bayreuth, Germany
Abstract. Gas sensors will play an essential role in future combustion-based mobility to effectively reduce emissions and monitor the exhausts reliably. In particular, an application in automotive exhausts is challenging due to the high gas temperatures that come along with highly dynamic flow rates. Recently, a thermoelectric hydrocarbon sensor was developed by using materials which are well known in the exhausts and therefore provide the required stability. As a sensing mechanism, the temperature difference that is generated between a catalytically activated area during the exothermic oxidation of said hydrocarbons and an inert area of the sensor is measured by a special screen-printed thermopile structure. As a matter of principle, this thermovoltage significantly depends on the mass flow rate of the exhausts under certain conditions. The present contribution helps to understand this cross effect and proposes a possible setup for its avoidance. By installing the sensor in the correct position of a bypass solution, the gas flow around the sensor is almost free of turbulence. Now, the signal depends only on the hydrocarbon concentration and not on the gas flow. Such a setup may open up new possibilities of applying novel sensors in automotive exhausts for on-board-measurement (OBM) purposes.
Citation: Hagen, G., Harsch, A., and Moos, R.: A pathway to eliminate the gas flow dependency of a hydrocarbon sensor for automotive exhaust applications, J. Sens. Sens. Syst., 7, 79-84, https://doi.org/10.5194/jsss-7-79-2018, 2018.

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Monitoring hydrocarbon concentrations in automotive exhausts is affected by flow rate changes. The signal of thermoelectric gas sensors is a thermovoltage. Its origin is a temperature difference that depends on the flow rate. To avoid this noise effect, the sensor can be installed in a defined bypass position. As shown by simulation and experiments, the gas flow around the sensor is almost turbulence-free and the signal only depends on the hydrocarbon concentration and not on the flow rate.
Monitoring hydrocarbon concentrations in automotive exhausts is affected by flow rate changes....
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