Conductometric Sensor for Soot Mass Flow Detection in Exhausts of Internal Combustion Engines

Abstract

Soot sensors are required for on-board diagnostics (OBD) of automotive diesel particulate filters (DPF) to detect filter failures. Widely used for this purpose are conductometric sensors, measuring an electrical current or resistance between two electrodes. Soot particles deposit on the electrodes, which leads to an increase in current or decrease in resistance. If installed upstream of a DPF, the “engine-out” soot emissions can also be determined directly by soot sensors. Sensors were characterized in diesel engine real exhausts under varying operation conditions and with two different kinds of diesel fuel. The sensor signal was correlated to the actual soot mass and particle number, measured with an SMPS. Sensor data and soot analytics (SMPS) agreed very well, an impressing linear correlation in a double logarithmic representation was found. This behavior was even independent of the used engine settings or of the biodiesel content.

Capacitive soot sensor for diesel exhausts

“…Regarding the sensor signal of the conductometric device (type 1), one can observe the well-known behavior, as often reported in literature [11][12][13][15][16][17][18][19][25][26][27]. As described above, after a certain blind time, the current increases monotonously with soot loading.…”

“…After switching off the heater, a new cycle started (for more details on the results of the conductometric devices see Ref. [18]). Capacitive devices were measured by an LCR-Meter (HP 4284A) at a constant frequency of 10 kHz in the R||C mode, i.e., the measured complex impedance is interpreted as a parallel circuit of R and C. The sensor signal, C, was recorded every second.…”

“…applying a conductometric soot sensor upstream of a DPF could basically enable also soot mass detection of the raw exhaust [18].…”

Comparative Study of Different Methods for Soot Sensing and Filter Monitoring in Diesel Exhausts

“…The sensor is briefly described below in Section 2.3 and in more detail in [16]. As a reference system, a commercial Pegasor soot sensing device was used.…”

Sensing of Soot Oxidation by Using Combustion-Type Sensor with Ag-Supported Catalyst

“…(3,7,8) For this reason, several soot detection technologies have been proposed by researchers in the last few decades. Potentiometric and amperometric soot sensors based on an oxide ion conductor (zirconia) and electrical insulator were proposed by Vogel and colleagues (8,9) and Moss and colleagues, (10)(11)(12) and these can be used for in situ measurements of soot concentration. Sensors based on the electromagnetic wave method, which includes radio-frequency (RF) (13,14) and optical waves in terms of changing the light transmission, scattering or extinction, have also been used to monitor PM concentration.…”