Charging-Based PN Sensing of Automotive Exhaust Particles

Abstract

Mobile measurement of particle number concentration (PN) in the exhaust of motor vehicles has recently become an integral part of emission legislation. Charge-based sensing techniques for the examination of PN, like Diffusion Charging (DC), represent a promising alternative to condensational particle counters (CPCs) as established PN sensors, because they enable to build robust, compact and energy efficient systems. However, due to the charging process, particle properties like size and morphology have a big impact on the sensor’s PN response. For particles of different size and shape we experimentally investigated those impacts using own-built charging-based sensors. The PN response of the DC sensor showed desired behavior for compact NaCl particles, but less satisfying behavior for combustion aerosol standard (CAST) particles, which is a widely used test aerosol for automotive applications. With a photoelectric charger, the PN response of CAST particles was significantly better.

Verifying the Efficiency of a Diesel Particulate Filter Using Particle Counters with Two Different Measurements in Periodic Technical Inspection of Vehicles

“…The relation of the size of the particles flowing through the filter is inversely proportional to the charging process, which allows the measurement of the number of particles with a size of 20-200 nm corresponding to the particles in the exhaust gas [13].…”

“…The effectiveness of the presented methods is still not sufficient during periodic technical inspections. The problem is either insufficient measurement accuracy, resulting, for example, from the diversity of solid particles structures and sizes [13], or the necessity of such an invasive intervention in the vehicle's exhaust system that it cannot be used for periodic technical inspection [12].…”

Analytical modeling and optimization of electrostatic particle sensors for particle number detection: incorporating particle size influence

“…The calculated charge from equation ( 10) is used for the calculation of the electrical mobility of the fragment. In the parallel and segmented case, x f can be calculated according to equation (6). For the arbitrary case, x f can be calculated by equation ( 9).…”

“…In addition to laboratory tests, PN emissions must also be measured under real driving conditions. Hence, the development of lightweight, robust, and cost-efficient onboard diagnostic sensors is crucial for conducting Real Driving Emission (RDE) measurements in compliance with the PMP [6,7]. On-board sensors can be utilized to detect particle filter failures and defeat devices, enhancing the overall effectiveness of emission control measures.…”