Novel Characterization of GDI Engine Exhaust for Gasoline and Mid-Level Gasoline-Alcohol Blends

Abstract

Gasoline direct injection (GDI) engines can offer improved fuel economy and higher performance over their port fuelinjected (PFI) counterparts, and are now appearing in increasingly more U.S. and European vehicles. Small displacement, turbocharged GDI engines are replacing large displacement engines, particularly in light-duty trucks and sport utility vehicles, in order for manufacturers to meet more stringent fuel economy standards. GDI engines typically emit the most particulate matter (PM) during periods of rich operation such as start-up and acceleration, and emissions of air toxics are also more likely during this condition. A 2.0 L GDI engine was operated at lambda of 0.91 at typical loads for acceleration (2600 rpm, 8 bar BMEP) on three different fuels; an 87 anti-knock index (AKI) gasoline (E0), 30% ethanol blended with the 87 AKI fuel (E30), and 48% isobutanol blended with the 87 AKI fuel. E30 was chosen to maximize octane enhancement while minimizing ethanol-blend level and iBu48 was chosen to match the same fuel oxygen level as E30. Particle size and number, organic carbon and elemental carbon (OC/EC), soot HC speciation, and aldehydes and ketones were all analyzed during the experiment. A new method for soot HC speciation is introduced using a direct, thermal desorption/pyrolysis inlet for the gas chromatograph (GC). Results showed high levels of aromatic compounds were present in the PM, including downstream of the catalyst, and the aldehydes were dominated by the alcohol blending.

The impact of ethanol and iso-butanol blends on gaseous and particulate emissions from two passenger cars equipped with spray-guided and wall-guided direct injection SI (spark ignition) engines

“…For the WG-SIDI vehicle, the application of higher alcohol blends led to marked reductions in particle number emissions, which is consistent with previous studies showing a reduced sooting tendency of alcohol fuels due to the presence of oxygen in the fuel [20,21,30,48,51]. The reduction in aromatics content in the fuels may also play some role in decreasing particle number emissions with increasing alcohol content.…”

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

“…The engines used in this study are a combination of different fuel injection strategies so a comparison between different injection methods can be made. It is known that fuel aromatic content and volatility affect particle emission rates (Khalek et al 2010;Kim et al 2013;Storey et al 2014). The test fuel was randomly selected commercially available gasoline fuel, in order to assess the variability in the emissions of the in-use fleet.…”

Impacts of Air-Fuel Stratification in ACI Combustion on Particulate Matter and Gaseous Emissions

“…This phenomenon has been observed by Maricq et al in PM measurements of gasoline vehicles that have very low solid PM [22]. In previous research on more conventional spark-ignited combustion [23,24], the correction has been applied with better agreement between TC and gravimetric PM. The discrepancy also points to potential problems with PM measurements during ACI operation.…”