Assessment Of A Reference Aerosol Generated By A Propane Diffusion Flame (Cast) In The Sub-23 Nm Range
Creators: name: Daskalos Emmanouil
name: Melas Anastasios
name: Deloglou Daniil
name: Zygogianni Alexandra
name: Papaioannou Eleni
name: Konstandopoulos Athanasios
Publisher: name: Zenodo
Year: 2017
Subjects: sub-23nm particles
soot aggregates
volatile matter

description: Concerns on negative effects of vehicle emissions, drove many countries to introduce emission standards. Existing European legislation regulates solid particles number according to the guidelines of the Particle Measurement Programme (PMP), not taking into account the sub-23 nm fraction of the exhaust emissions due to size related inherent difficulties that lead to measurement uncertainties (Giechaskiel et al. 2008). However, as recommended by the JRC Science and Policy Report (Giechaskiel and Martini, 2014), there is an urgent need for an updated version of the regulations that would take into consideration sub-23 nm particles by further reducing the cut-off particle size limit. Towards this target, research efforts focus on robust sampling and measuring in the sub-23 nm particle size range.

In order to validate experimental measurement and sampling setups a reference aerosol is needed to generate particles in the size range of interest in a consistent and repeatable way. Specifically, in the automotive sector the use of a propane diffusion flame soot generator (Combustion Aerosol Standard, CAST) can be of value due to its ability to generate repeatable soot particle distributions. A characterization of solid soot particles from CAST has been presented in (Konstandopoulos et al. 2011). However, recent studies show that CAST-generated particles may contain volatile fraction under specific operation conditions. These findings question the applicability of CAST in several applications, e.g. as a solid particle generator (Mamakos et al., 2013).

Herein, we will study the volatile fraction and the structure of CAST-generated particles for particle sizes used in the current PMP but also in the sub-23 nm region. More specifically, the particle size distribution of CAST-generated particles is altered by controlling the flow of a mixing gas (N2) that dilutes the fuel (propane). Figure 1 shows particle size distributions of CAST-generated particles that have been obtained in the sub-23 nm region. Particles with mean mobility diameter in the range of 10-100 nm are generated and their size distribution is measured with Scanning Mobility Particle Sizer (SMPS) by using a long DMA (TSI 3081) for larger sizes and a nano-DMA (TSI, 3085) for sub-23 nm particles. The volatile fraction of CAST-generated particles is measured by thermo-gravimetric analysis of filtered samples under nitrogen. Microstructural analysis is performed by applying two different approaches; Transmission Electron Microscopy (TEM) image analysis and tandem mobility-aerodynamic diameter measurements (Baltzopoulou et al., 2012). The particle collection on TEM grids is done with an in-house developed thermophoretic sampler (Konstandopoulos et al. 2011). Finally, particle losses and possible volatile material evaporation are both numerically and experimentally studied by passing the CAST-generated particles through a PMP-compliant Volatile Particle Remover.
description: {"references": ["Giechaskiel, B., Dilara, P., and Andersson, J. (2008), Aerosol Sci. Technol. 42, 528\u2013543.", "Giechaskiel B., Martini G. (2014), JRC Science and Policy Report: \"Review on engine exhaust sub-23 nm particles\", Joint Research Centre.", "Konstandopoulos, A. G., Daskalos, E., and Vlachos, N. (2011), 15th ETH-Conference on Combustion Generated Nanoparticles, June 26\u201329, Zurich, Switzerland.", "Mamakos A., Khalek I., Giannelli R. and Spears M. (2013), Aerosol Sci. Technol. 47, 927-936.", "Baltzopoulou P., Kostoglou M., Papaioannou E. and Konstandopoulos A. (2012), European Aerosol Conference EAC 2012, EAC-2012-P074, September 2-7, Granada, Spain."]}