Andrea Geupel

Determination of the NOx Loading of an Automotive Lean NOx Trap by Directly Monitoring the Electrical Properties of the Catalyst Material Itself

Recently, it has been shown that the degree of loading of several types of automotive exhaust aftertreatment devices can be directly monitored in situ and in a contactless way by a microwave-based method. The goal of this study was to clarify whether this method can also be applied to NOx storage and reduction catalysts (lean NOx traps) in order to obtain further knowledge about the reactions occurring in the catalyst and to compare the results with those obtained by wirebound NOx loading sensors. It is shown that both methods are able to detect the different catalyst loading states. However, the sensitivity of the microwave-based method turned out to be small compared to that previously observed for other exhaust aftertreatment devices. This may limit the practical applicability of the microwave-based NOx loading detection in lean NOx traps.

Platform for a hydrocarbon exhaust gas sensor utilizing a pumping cell and a conductometric sensor

Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well.

Cumulative Measurement Principle For The Detection Of Small Amounts Of Gaseous Species

To control or monitor processes and the compliance with air quality regulation, highly selective and long‐term stable gas sensors with a high accuracy in the low ppm detection range are needed. Gas sensor techniques detecting the actual concentration of analyte species often suffer from inaccuracy at low concentrations and signal instability. In contrast, gas sensors detecting the cumulative analyte amount during the measurement period are beneficial for monitoring very small amounts. The idea of the cumulative detection principle is the accumulation of the gas molecules in the sensitive layer and therefore measuring the timely integrated concentration of the gas species (“the amount”). Hence, the sensitive layer of the cumulative sensor consists of a gas storage material, which is able to store selectively the analyte molecules via a chemical bonding and thereby changes its electrical properties. In this work, the principle and the benefits of the cumulative detection is described. As an example, measure...