Particle Emissions from Gasoline Direct Injection Engines During Engine Start-Up (Cranking) 2019-01-1182
Engine start-up (cranking) can be an important source of particle emissions from vehicles. This phenomenon is commonly encountered in parking lots, garages at homes, shopping centers and malls. This is also encountered in traffic with hybrid vehicles alternating between electric motor and internal combustion engine, and with vehicles utilizing a start/stop strategy for fuel economy saving. Earlier research has shown that start-up emissions from vehicles equipped with gasoline direct injection (GDI) engines can be more than diesel vehicles equipped with diesel particulate filter (DPF). 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 implication and importance of engine start up, in particular, cranking. 11 commercially available gasoline fuels were tested on a naturally aspirated GDI vehicle, 3 among these commercially available fuels were tested on another turbocharged GDI vehicle, and 18 blended gasoline fuels were tested on 12 other GDI vehicles (7 turbocharged and 5 naturally aspirated). The cranking event was defined as the first 25 seconds 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 49) 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 PM index. Analysis between the cranking event particle emissions and other fuel properties such as T60, T70, T80, T90, EP and total aromatics content also didn’t 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 indicate that start-up emissions could be independent of fuel properties. Future research activities on start-up particle emissions should include other engine technologies and explore the possibility of reducing such emissions.