Effects of Gasoline Direct Injection Engine Operating Parameters on Particle Number Emissions

Abstract

A single-cylinder, wall-guided, spark ignition direct injection engine was used to study the impact of engine operating parameters on engine-out particle number (PN) emissions. Experiments were conducted with certification gasoline and a splash blend of 20% fuel grade ethanol in gasoline (E20), at four steady-state engine operating conditions. Independent engine control parameter sweeps were conducted including start of injection, injection pressure, spark timing, exhaust cam phasing, intake cam phasing, and air−fuel ratio. The results show that fuel injection timing is the dominant factor impacting PN emissions from this wall-guided gasoline direct injection engine. The major factor causing high PN emissions is fuel liquid impingement on the piston bowl. By avoiding fuel impingement, more than an order of magnitude reduction in PN emission was observed. Increasing fuel injection pressure reduces PN emissions because of smaller fuel droplet size and faster fuel−air mixing. PN emissions are insensitive to cam phasing and spark timing, especially at high engine load. Cold engine conditions produce higher PN emissions than hot engine conditions due to slower fuel vaporization and thus less fuel−air homogeneity during the combustion process. E20 produces lower PN emissions at low and medium loads if fuel liquid impingement on piston bowl is avoided. At high load or if there is fuel liquid impingement on piston bowl and/or cylinder wall, E20 tends to produce higher PN emissions. This is probably a function of the higher heat of vaporization of ethanol, which slows the vaporization of other fuel components from surfaces and may create local fuel-rich combustion or even pool-fires.

Size distribution, chemical composition and oxidation reactivity of particulate matter from gasoline direct injection (GDI) engine fueled with ethanol-gasoline fuel

“…The experiments conducted by Zhang et al [17] were at low speed and high load condition (2000 rpm, 210 Nm), it was found that the E10 and E20 fuels reduced PN emissions from GDI engine. While others [18,19] have reached opposite conclusions. Wang et al [19] found ethanol addition increased the PN emissions, the experiments were at low speed and low load conditions (1500 rpm, 3.5e8.5 bar BMEP).…”

Comparative nanostructure analysis of gasoline turbocharged direct injection and diesel soot-in-oil with carbon black

“…Oxidation is pervasive throughout the soot formation process due to the highly oxidizing conditions within the cylinder, and acts to reduce the size and number of the soot nanoparticles produced. Both the formation and oxidation are highly dependent on the engine operating conditions, such as injection modes [8,9], cold start conditions [10,11] or engine speed and load [10,12,13].…”

Effective Density and Volatility of Particles Emitted from Gasoline Direct Injection Vehicles and Implications for Particle Mass Measurement

“…Gasoline direct injection (GDI) engines are widely used because of their higher specific power output and fuel economy compared to conventional port injection gasoline engines (He et al 2012). According to the European commission, 35% of vehicles will be gasoline direct injection vehicles by 2020 (Mamakos 2011).…”