Effect of Ultra-High Fuel Injection Pressure on Combustion Characteristics, Engine Performance and Pollutant Emissions of a Multi-Cylinder Engine

The concern about CO2 emissions from commercial vehicles powered with internal combustion engines has been motivating research and development projects to reduce the transportation sector carbon footprint. One of the promising alternatives is the use of biofuels associated with high-efficient internal combustion engines, taking advantage of the current infrastructure of car manufacturers and automotive suppliers, as well as of the potential growth in biofuel production. With the stringent emissions regulations, the use of downsized SI engines for passenger cars has driven the adoption of direct injection technology, enabling the use of different fuel injection strategies such as stratified mixtures and multiple injection events, as well as the increase of the compression ratio as a way to improve engine thermal efficiency. This path also led to a gradual increase in injection pressure, aiming to improve spray formation and reduce the formation of particulate matter. In this sense, the implementation of such technology on the Brazilian flex-fuel engine represents an important path to the transport sector decarbonization. However, the use of hydrous ethanol and gasoline-anhydrous ethanol blends on direct injection systems still demands fundamental research to fully understand the potential benefits and drawbacks of higher fuel injection pressures. Within this framework, this work aims to further understand the effect of using ultra-high fuel injection pressures (up to 1000 bar) on engine performance and pollutant emissions of a multi-cylinder prototype engine. Experimental tests with three different injection pressures confirmed the HC and soot emission reduction, as well as improvement on the engine brake thermal efficiency both when fueled with hydrous ethanol and Brazilian gasohol (blend of 27% anhydrous ethanol in gasoline). Due to the lack of dedicated hardware to pressurize and inject ethanol at ultra-high pressures, the durability of the injection components was a major concern during the experimental campaign.