Measurement of Sub-23 nm particles emitted by gasoline direct injection engine with new advanced instrumentation

Abstract

The research on health effects of soot particles has demonstrated their toxic impact on humans, especially for the smallest ones that can pass through the lungs into the bloodstream and be transferred to other parts of the body. Since the Euro 5b regulation, the total particle number (PN) at the exhaust is limited, but the associated protocol developed by the Particle Measurement Program (PMP) group defined a counting efficiency at the 23 nm cut-off particle diameter to avoid measurement artefacts [1][2]. Recent studies have demonstrated that the last generation Euro 6 engines can emit as many particles in the range 10-23 nm as beyond 23 nm [3]. The SUREAL-23 project (Understanding, Measuring and Regulating Sub-23 nm Particle Emissions from Direct Injection Engines Including Real Driving Conditions), funded by Horizon 2020 EU-program, aims to develop sampling, conditioning and measuring instruments and associated methodologies to extend the existing protocol down to at least 10 nm. This measurement setup was evaluated on various light duty direct injection platforms. This communication focuses on a gasoline-DI vehicle with a Euro 6b engine. Tests were conducted on multiple operating conditions (moderate and aggressive driving cycles, hot and cold starts, and several fuel and lubricant formulations). Sampling and conditioning were done with a two-stage dilution system, with a built-in catalytic stripper. The prototype instruments have been compared to commercial reference soot particle analyzers (TSI CPC, Horiba MEXA-2000 SPCS and Cambustion DMS500). A good consistency between all the measurements was demonstrated, with a satisfactory repeatability and robustness of the proposed measurement setup and of the associated methodology. An on-board version of the proposed setup is currently being developed to allow PN measurement in Real Driving Emissions (RDE) conditions.