A study has been conducted to measure the particle number emissions from a current-generation 1.6-liter, Euro IV-compliant turbo-charged Gasoline Direct Injection (GDI) passenger car engine. A fast-response particle size spectrometer was used along with a PMP-compliant particulate measurement system to measure the effect of various engine parameters on the particulate emissions during the New European Drive Cycle (NEDC).
Overall particle number is shown along with further analysis of the transient particle emissions. The cold start clearly affects particle formation with approximately 50% of the cumulative particle number being emitted within 200 seconds of the start. Even beyond 200 seconds, the particle number emissions fall as the test progresses and are generally consistent with increases in engine coolant temperature indicating that cold engine fuel preparation issues are contributing to the particle number count.
The data from the fast-response particle size spectrometer sampling directly from the exhaust showed very rapid increases in particle emissions during engine transients. Correlation with lambda was shown with rich lambda transients resulting in significant increases in particle emissions. Changes in other engine parameters, notably engine fuelling and spark timing, were also seen to affect particle number.
Particle size information was also analyzed at high frequency. This showed wide ranges in accumulation mode particle size over short periods of time with larger accumulation mode particles seen during higher load conditions and smaller particles seen at low load and idle. At times the accumulation mode exhibited two distinct peaks of both larger and smaller particles simultaneously suggesting two distinct mechanisms of accumulation mode particle formation.