Optimization of soot deposition by high-temperature prepolarization of a resistive particulate matter sensor

Jens Ebel,Holger Fritze,Carolin Schilling

doi:10.5194/jsss-9-263-2020

Abstract

Abstract. For the purposes of the onboard diagnosis (OBD) of diesel particulate filters (DPFs) in diesel exhaust treatment systems, a particulate matter (PM) sensor is applied downstream from the DPFs to detect small amounts of diesel soot that passed through the filter. The state-of-the-art technology is a sensor based on the resistive measurement principle, i.e., charged soot particles are attracted by electrophoretic forces, deposited on an interdigital electrode (IDE) structure and conductive soot bridges that reduce the overall resistance are formed. This paper reports how the response time of a resistively working particulate matter sensor can be shortened up to 30 % by the optimization of soot deposition that is initiated by a change in the sensor operation strategy. The measurement voltage is applied for prepolarization during the sensor regeneration phase rather than during the cooling phase before the measurement is commonly done. Experiments were performed at diesel engine test benches to examine this context and simulations of the electric field above and below the IDE structure. The data are used to deduct a model, including the solid state chemistry of the sensor's ceramic materials, the effect of impurities on the electric field properties and the interconnection with the soot deposition, which defines the sensor's response.

Highlights

Particulate matter (PM) emissions of internal combustion engines, especially diesel combustion, are said to cause serious health problems (Newell et al, 2017)
PM emitted by gasoline engines is smaller in size compared to diesel PM, so in the case of a future gasoline particulate matter filter (GPF) onboard diagnosis (OBD) for very low masses needs to be detected to ensure that the particle number (PN) limit holds (Harris and Maricq, 2001)
The application of the measurement voltage causes a slight displacement of sodium at the electrodes, leaving the negative charge behind to form a space charge region, while the electronic conductivity is too low for entire discharge

Summary

Introduction

Particulate matter (PM) emissions of internal combustion engines, especially diesel combustion, are said to cause serious health problems (Newell et al, 2017). The state-of-theart technology to reduce PM emissions in automotive exhaust aftertreatments includes ceramic wall flow diesel particulate matter filters (DPFs) which need to be regenerated when the PM load reaches a certain level. To ensure onboard diagnosis (OBD) of the DPFs, a PM sensor is applied downstream from the DPFs to detect soot particles passing through the filter in case of a malfunction (Bargende et al, 2016; Ochs et al, 2010). PM emitted by gasoline engines is smaller in size compared to diesel PM, so in the case of a future gasoline particulate matter filter (GPF) OBD for very low masses needs to be detected to ensure that the PN limit holds (Harris and Maricq, 2001). As a way to shorten the response time, Middelburg discussed the possibility of trans-

Results

Discussion

Conclusion