Particulate Matter Emission Comparison of Spark Ignition Direct Injection (SIDI) and Port Fuel Injection (PFI) Operation of a Boosted Gasoline Engine

Abstract

Spark ignition direct injection (SIDI) gasoline engines, especially in downsized boosted engine platforms, are increasing their market share relative to port fuel injection (PFI) engines in U.S., European and Chinese vehicles due to better fuel economy by enabling higher compression ratios and higher specific power output. However, particulate matter (PM) emissions from engines are becoming a concern due to adverse human health and environment effects, and more stringent emission standards. To conduct a PM number and size comparison between SIDI and PFI systems, a 2.0L boosted gasoline engine has been equipped and tested with both systems at different loads, air fuel ratios, spark tim ings, fuel pressures and injection timings for SIDI operation and loads, air fuel ratios and spark timings for PFI operation. Regardless of load, air fuel ratio, spark timing, fuel pressure, and injection timing, particle size distribution from SIDI and PFI is shown to be bimodal, exhibiting nucleation and accumulation mode particles. SIDI produces parti cle numbers that are an order of magnitude greater than PFI. Particle number can be reduced by retarding spark timing and operating the engine lean, both for SIDI and PFI operation. Increasing fuel injection pressure and optimizing injection timing with SIDI also reduces PM emissions. This study provides insight into the differences in PM emis sions from boosted SIDI and PFI engines and an evaluation of PM reduction potential by varying engine operating parameters in boosted SIDI and PFI gasoline engines.

Physical, chemical, and toxicological characteristics of particulate emissions from current technology gasoline direct injection vehicles

“…The increase in particulate emissions for GDI engines is likely due to the increased liquid fuel impingement on the combustion chamber walls that can result in liquid fuel that is not totally vaporized and well mixed at the start of combustion. This is turn may cause fuel pool fires generating higher PM emissions (Su et al, 2014;Szybist et al, 2011).…”

Effects of split and single injection strategies on particle number emission and combustion of a GDI engine

“…Meanwhile, it is widely reported that the particle emission from GDI engines is mainly caused by two types of fuel-rich combustion: (1) locally fuel-rich mixture in the combustion chamber and (2) diffusion-controlled burning of thin films of liquid fuel on the piston or cylinder wall. 8 When the injection timing is advanced, as the distance between injector and piston top surface becomes smaller, it is easy for the fuel spray to touch the piston top surface and wall-wetting phenomenon is obvious. For the injection timing of 270 °CA BTDC, the distance between the injector and piston surface is about 4.8 cm at the beginning of fuel injection, while it is only about 1.5 cm at injection timing of 320 °CA BTDC.…”

“…According to a proposal issued by the European Commission, PM number over the New European Driving Cycle (NEDC) for spark ignition direct injection (SIDI) engine powered vehicles will be limited to 6.0E12 particles per kilometer in 2014 and 6.0E11 particles per kilometer in 2017. 8 Given that, how the GDI improves the particulate emission has become a hot area of research in the field of internal combustion engine. 6,9,10…”

“…According to a proposal issued by the European Commission, PM number over the New European Driving Cycle (NEDC) for spark ignition direct injection (SIDI) engine powered vehicles will be limited to 6.0E12 particles per kilometer in 2014 and 6.0E11 particles per kilometer in 2017. 8 Given that, how the GDI improves the particulate emission has become a hot area of research in the field of internal combustion engine. 6,9,10 In literature, 8,11 it is indicated that when the fuel injection is too early, the possibilities of wall impingement of fuel spray and wetted wall are increased, but when the injection timing is too late, the fuel-air mixing time is shortened.…”

Effects of external cooled EGR on particle number emissions under cold and warm spark-ignition direct-injection engine conditions

“…In the European automotive market, overall share of SIDI vehicles increased sharply beginning in 2008, and is estimated at around 35 % in 2014 [7]. However, It is well known that the PN and particle mass emissions from SIDI engine are higher than that from PFI engine, both at steady-state and driving cycle conditions [8,9]. The increase in particle emissions can be mainly attributed to three types of rich combustion: (1) locally fuel-rich mixture in the combustion chamber, (2) diffusion-controlled burning THERMAL SCIENCE: Year 2018, Vol.…”