Modern fuels and catalytic technologies for low emissions in gasoline direct injection engines

The requirements for controlling Particulate Matter (PM) and gaseous emissions emitted from gasoline direct injection (GDI) engines, especially under cold start conditions, and the introduction of bio-alcohols fuels in the market demands the development of novel efficient aftertreatment technologies. Understanding the PM characteristics from the combustion of different fuels it is a key step in the design of next generation of catalysts and aftertreatment systems, including three-way catalyst (TWC) and catalyst coated or not gasoline particulate filters (GPFs). The research study presented in this thesis provides a detailed understanding of the synergies between bio-alcohols derived fuels combustion in GDI engines and novel aftertreatment technologies on the control of PM and gaseous emissions. The effect of the physico-chemical properties of bio-alcohol fuel blends on combustion and emissions at warm steady-state and cold start engine conditions has been investigated. Bio-butanol fuel blend has been further explored at different engine loads in combination with exhaust gas recirculation (EGR) technology. An extensive characterization of the PM emissions has been carried out using several methodologies and techniques such as high resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), scanning mobility particle sizer (SMPS) and Raman spectroscopy. The combustion of bio-alcohols resulted in a significant reduction of 60% - 80% of PM emissions with the modification in their structural characteristics, leading to agglomerates with smaller primary particles (≈1-3 nm) and fractal dimensions and, soot with higher tortuosity (≈3.1 %) as TEM revealed. Under cold start event, bioalcohols emitted more reactive and less mature soot (i.e. higher organic content and impurities) as found from TGA and Raman analysis compared to soot emitted from gasoline fuel combustion. The TWC activity was improved between 4.3% and 1.5% in the exhaust stream from the bio-alcohols combustion. The aftertreatment architectures, including either coated GPFs or not and arrangement in the exhaust (i.e. upstream or downstream of the TWC) has shown a significantly impact on the TWC activity, reducing light-off temperatures up to 20°C. Catalytic GPF showed high performance to efficiently filter PM and removed gaseous emissions from GDI combustion with acceptable pressure drop