Particle Emissions from Gasoline Direct Injection Engines during Engine Start-Up (Cranking)

摘要

Engine start-up (cranking) can be an important source of particle emissions from vehicles. With the penetration of GDI vehicles in the global vehicle fleet, it is important to analyze and understand the contribution of start-up particle emissions from GDI vehicles, and the potential effects of fuel properties on that process. In this work, chassis dynamometer based investigation on the effect of several gasoline fuels (commercial and blended) on both, naturally aspirated and turbocharged GDI vehicles were conducted to understand the importance of engine start up, in particular, cranking. 10 commercially available gasoline fuels were tested on a naturally aspirated 2010 model year GDI vehicle, 3 among these commercially available fuels were tested on another 2009 model year turbocharged GDI vehicle, and 8 blended gasoline fuels were tested on 12 other GDI vehicles (7 turbocharged and 5 naturally aspirated) ranging in model years 2011-2015. The cranking event was defined as the first 25 seconds (inclusive of transport time to sample point) of the cold-start phase (Phase 1) and hot-start phase (Phase 3) of the FTP-75 and/or LA-92 drive cycles. Real-time solid particle number measurement was performed using SwRI’s Solid Particle Number System in accordance with European Union Particle Measurement Programme (Regulation Number 83) methods, and real-time soot mass measurement was performed using AVL Micro-soot Sensor (MSS). Typically, it was observed that the cold-start cranking event solid particle number emissions contributed 2% to 30% of the overall cycle and 4% to 35% of the cold-start phase (Phase 1) emissions. Interestingly, while the cold-start phase (Phase 1) particle emissions correlated very well with the PM index (R2 > ～0.9), no strong relationship was observed between the cranking event particle emissions and the fuel PM index. Analysis between the cranking event particle emissions and other fuel properties such as T50, T60 and total aromatics content also did not indicate any relationship. This work highlights that the cranking event is a unique important contributor to particle emissions under cold-start conditions. Further, results observed in this study suggests that start-up emissions could be independent of fuel properties.