Development of a Spark Discharge PM Sensor for Measurement of Engine-Out Soot Emissions

There is interest in measuring the engine-out particulate emissions from diesel engines in real time in order to optimize the engine control strategies such as exhaust gas recirculation (EGR) and monitor the loading of the particulate filter. This paper presents experimental results obtained using a measurement technique that produced a signal proportional to the peak voltage of a spark discharge that was exposed to the exhaust gas. The sensor was tested on a turbocharged diesel engine with exhaust soot levels from $<0.1FSN$ to $>3.5FSN$⁠, and compared with reference measurements of filter smoke number (FSN) from an AVL 415S smokemeter. The sensor signal showed a high correlation with the reference FSN measurements. Conversion of the FSN values to mass concentration values (using published techniques for the reference instrument) indicated that the output of the spark discharge soot sensor was nearly linear with mass concentration over a substantial portion of the measuring range. The sensor showed a response time of less than 2 s to step changes in FSN levels.