Solid Nucleation Mode Engine Exhaust Particles Detection at High Temperatures with an Advanced Half Mini DMA 2019-24-0052

Diesel and gasoline direct injection engines emit nucleation mode particles either under special conditions or as part of their normally emitted size distribution, respectively. Currently, European legislation excludes nucleation mode particles as particle number vehicle emission measurements are limited down to 23 nm. The rationale behind such a cut-off size is based on the avoidance of significant uncertainties inherent in the sampling and measuring of sub-23 nm solid particles. However, the sub-23 nm particles have drawn increased attention since a large fraction of particles emitted by modern vehicles lies in this size range. In this study we investigate the possibility of accurate nucleation mode particles detection by using the Advanced Half Mini Differential Mobility Analyzer (HM-DMA). The Advanced HM-DMA system is able to classify aerosol particles in the mobility size range 5 - 30 nm with high resolution and fast spectrum acquisition that can accommodate a sample flow maintained at up to 200°C. The unique ability to classify particles at high temperatures permits engine exhaust measurements without the need for aerosol conditioning. Initially, the Advanced HM-DMA hot operation mode accuracy is tested with reference aerosols against State-of-the-Art instruments. Thereafter, the Advanced HM-DMA is employed for measuring nucleation mode particles generated by a diesel engine using a single hot dilution step. Advanced HM-DMA measurements are compared to measurements performed with PMP protocol-compliant volatile particle removal system. The excellent agreement between the two measurements confirms the reliability of the Advanced HM-DMA hot operation mode and indicates the possibility of using a simplified conditioning setup for solid nucleation-mode particles measurement.