Simulation and Experiments with a Modular Electrical Particle Detector

Description

With the latest updates of emission legislations for motor vehicles (Real Driving Emissions (RDE), exhaust examination Germany1), mobile determination of Particle Number (PN) has become mandatory. Established sensor technology for PN measurement – based on condensational particle counters – is hardly applicable for mobile PN measurements. A promising alternative to that technology is diffusion charging (DC), which consists of charging and subsequent current measurement of aerosol particles. DC enables to build compact, robust and lightweight PN sensors. However, its sensor response suffers from a strong dependency on the particle’s size, which distorts the measurement.
In order to reduce the size dependency of the sensor signal, DC can be implemented in various configurations. The basic configuration consists of two stages, (i) modulated particle charging and (ii) current measurement using a Faraday cage electrometer (FCEM). This basic configuration can be extended by an electrostatic precipitation (ESP) stage (as suggested by Burtscher2) and another FCEM (Meier3). The mentioned sensor stages can be combined and operated in different ways, leading to different DC configurations and corresponding response characteristics. The aim of this study is to find the best configuration with respect to size dependency of the sensor response.
For that purpose, a 3D multiphysical finite element method model was developed. The model was applied to three different DC configurations. A modulated precipitation configuration showed the best results. Additionally, a modular electrical particle detector was designed, consisting of different charging stages, an ESP and two FCEMs. This device allows for the experimental investigation of the DC configurations used in the simulations. First experimental results nicely agree with the simulation results, however, further experimental work is ongoing to validate the findings.

1 Änderung der Richtlinie für die Durchführung der Untersuchung der Abgase von Kraftfahrzeugen nach Nummer 6.8.2 der Anlage VIIIa Straßenverkehrs-Zulassungs-Ordnung (StVZO) (AU- Richtlinie)
2 Burtscher H., Schmidt-Ott A. (2006), EP 1 655 595 A1
3 D.Meier, D.Egli, P.Steigmeier, H.Burtscher and M.Fierz; “Miniature electrical nanoparticle detector for simultaneous measurement of particle number, average size and lung-deposited surface area”, 22nd European Aerosol Conference, Tours, 2016

Period	17 Oct 2017
Degree of Recognition	International