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.
Highlights
Examination of particle number concentration (PN) emissions for type approval of passenger cars is done on test beds according to the particle measurement program (PMP) [1], where a condensational particle counters (CPCs) [2] is typically used as PN sensor.new regulations require PN measurements apart from laboratory environment, such as on-board determination [3], or PN monitoring during the vehicle’s lifecycle in the course of periodical technical inspections (PTI) [4]
Examination of PN emissions for type approval of passenger cars is done on test beds according to the particle measurement program (PMP) [1], where a CPC [2] is typically used as PN sensor
Diffusion chargers can be used for that purpose, due to the charging process their PN sensor response significantly depends on the particle size [5]
Summary
Examination of PN emissions for type approval of passenger cars is done on test beds according to the particle measurement program (PMP) [1], where a CPC [2] is typically used as PN sensor. New regulations require PN measurements apart from laboratory environment, such as on-board determination (known as real driving emissions RDE) [3], or PN monitoring during the vehicle’s lifecycle in the course of periodical technical inspections (PTI) [4]. For both methods, simpler exhaust conditioning and more robust, compact and light-weight sensors are needed. Diffusion chargers can be used for that purpose, due to the charging process their PN sensor response significantly depends on the particle size [5]. To diffusion charging, particles can be charged via the direct photoelectric effect using a light source with sufficient energy to overcome the particle’s material work function [7]
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