In-line, Real-time Particulate Matter Sensors for OBD and Exhaust After-treatment System Control Applications

The ability to quantify particle mass and number concentrations in the exhaust stream of combustion engines during in-use operation is of critical importance for continuously monitoring and diagnosing the particulate matter removal efficiency of modern exhaust gas after-treatment systems. Extensive literature survey suggested a sensor operating on the diffusion-charging principle being optimally suited for particle measurements due to their proportional response towards particle surface area. This study was designed to determine and assess the possibility of quantifying particle emissions during on-road measurements using a prototype diffusion-charging type sensor. Such a sensor would not only allow for continuous monitoring capabilities of the exhaust particulate filters integrity, but moreover provide for a simplified tool to assess real-world particle number emissions to verify in-use emissions compliance of engines.;Evaluation of the sensor followed a three tier process, starting with fundamental sensor response analysis using a particle generator in order to develop and parameterize the underlying physical phenomena of the measurement principle. Next, examine the sensor in engine dynamometer experiments under controlled environment, and sampling from test vehicles during chassis dynamometer testing aimed at real-world like test conditions. Finally, the sensor was installed on vehicles while operated on the road over diverse driving conditions. This allowed for comparison to laboratory-grade measurement systems and the standard regulatory gravimetric particulate matter measurement method. The diffusion-charging type sensor employed in this study was observed to exhibit a response proportional to particle size Dp 1.09 and a measurement variability below 2% over consecutive tests. The sensor\u27s sensitivity allowed for distinguishing between Diesel particulate filter efficiencies due to soot cake layer build-up on the substrate walls. In summary, the study concluded that the diffusion-charging type sensor provided a viable method to quantify in-use particle number emissions