Engine Exhaust Solid Sub-23 nm Particles: I. Literature Survey

In the current vehicle exhaust legislation particle number (PN) limits for solid particles >23 nm are prescribed. The legislation was extended to include gasoline direct injection (G-DI) vehicles since 2014 and will be applied to non-road mobile machinery. Target of this paper was to investigate whether existing PN measurement equipment are capable of measuring below 23 nm. More specifically, it was investigated 1) whether all volatile particles can be removed efficiently in the PN measurement systems 2) whether any artifacts happen in the PN systems (e.g. formation of non-volatile particles due to pyrolysis), and 3) whether by lowering the lower size the measurement uncertainty increases significantly. The main conclusions are: 1) The volatiles are not always removed efficiently in the PN measurement systems. The major issue is re-nucleation of sulfuric acid downstream of the evaporation tube. These particles typically do not grow at sizes above 23 nm. 2) There are indications of formation of 10 nm solid particles from hydrocarbons and sulfuric acid in the PN systems. 3) The measurement uncertainty due to differences between commercial systems will increase. It is estimated to be around 5% for measurements >10 nm, when no separate solid nucleation mode exists. Recommendations for proper measurements below 23 nm are given.

GIECHASKIEL Barouch;  MANFREDI Urbano;  MARTINI Giorgio; 

2014-11-17

SOCIETY OF AUTOMOTIVE ENGINEERS

JRC88730

1946-3952,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC88730,   

10.4271/2014-01-2834,