Peripheral fuel injection (PeFI) to improve efficiency and emissions in diesel engines

In diesel engines, injectors with multiple orifices are located typically at the center of the combustion chamber, spraying fuel radially toward the cylinder wall. Although this arrangement is universally used in conventional diesel combustion (CDC), it has inherent drawbacks with regards to emissions and efficiency. Jet impingement at the cylinder wall leads to flame extinction as well as increased heat loss to the coolant. These events promote higher levels of soot, unburned hydrocarbons, and carbon monoxide emissions. Engine efficiency also suffers because of the higher cooling requirement. In this study, we explore a peripheral fuel injection (PeFI) concept, developed by our group, through experimental testing for the first time in a single cylinder research engine (Caterpillar 3401) modified with a custom-designed cylinder head. PeFI consists of multiple single-hole injectors located in the engine head along the periphery of the cylinder. Based on prior studies in a non-reacting chamber and three-dimensional computational fluid dynamics simulations, PeFI injectors were oriented to spray fuel at an angle of 30° relative to the chamber radius. Experiments at a constant engine speed were performed for sweeps of rail pressure and start-of-injection (SOI) timing, with the goal to directly compare the performance of CDC and PeFI at various operating conditions. At points of highest efficiency operation, data revealed negligible soot and up to 73% reduction in CO levels for PeFI cases compared to those for CDC cases. Switching from CDC to PeFI also decreased heat loss to the coolant and increased the engine efficiency by up to 1.6% points. Test results substantiate PeFI’s ability to improve fuel-air mixing, avoid fuel/flame impingement on piston/wall, and reduce coolant heat loss. These inherent features show promising potential of PeFI to simultaneously reduce emissions and increase efficiency in modern diesel engines.