Electronic Particulate Matter Sensor – Mechanisms and Application in a Modern Light-Duty Diesel Vehicle

An electronic particulate matter sensor (EPMS) developed at the University of Texas was used to characterize exhaust gases from a single-cylinder diesel engine and a light-duty diesel vehicle. Measurements were made during transient tip-in events with multiple sensor configurations in the single-cylinder engine. The sensor was operated in two modes: one with the electric field energized, and the other with no electric field present. In each mode, different characteristic signals were produced in response to a tip-in event, highlighting the two primary mechanisms of sensor operation. The sensor responded to both the natural charge of the particulate matter (PM) emitted from the engine, and was also found to create a signal by charging neutral particles. The characteristics of the two mechanisms of operation are discussed as well as their implications on the placement and operation of the sensor. By comparing the signals from sensors stationed at different distances downstream from the exhaust valve, the speed of travel of PM in various phases of the tip-in event was measured.

The vehicle used for testing had a 1.9 liter Fiat/Opel turbo-diesel engine and was without a DPF. The sensor was able to measure trends in both steady state and transient PM concentrations as the vehicle was driven on city streets. PM emissions were high for pedal positions greater than about 40% of full range, and high transient PM emissions were often associated with rapid lift-off of the pedal and during engine braking. The sensor showed good durability over several hours of driving.