Characteristics of Particle Number and Particle Mass Emissions of a Diesel Engine during Cold-, Warm-, and Hot-Start Operation

Diesel engine cold start is emerging as a critical topic of investigation. Of key importance is the impact the warm-up period has on particulate emissions. Presented in this work is a fundamental and comprehensive study on the impact of cold, warm, and hot start on particulate emissions over a custom quasi-steady-state drive cycle discretized by frequent engine stop/start. The experiments were conducted on a six-cylinder, turbocharged, diesel engine. Compared with cold start, the count median diameter (CMD) increased by 16% and 5% in the Aitken mode at 1500 rpm and 2000 rpm, respectively, when the engine was fully warmed up. The geometric standard deviation (GSD) decreased as the engine warmed up. Particle number (PN) concentration decreased by 50% as the engine coolant temperature reached 70°C, compared to cold start (23°C), and a strong positive linear correlation was found between the particle mass (PM) and PN emissions at all loads. This work explores the topic of engine warm-up with respect to particulate emissions with a rigor not previously done.