The Use of Split-Injection Technique and Ethanol Lean Combustion on a SIDI Engine Operation for Reducing the Fuel Consumption and Pollutant Emissions

The current energy and climate world condition presents the need for development of increasingly efficient and sustainable internal combustion engines. In order to meet these requirements, environmental regulatory agencies establish long-term goals of fuel consumption and pollutant gases emissions reduction, which in turn lead the engines to a constant evolution. Thus, this work exploits some recent technologies that tend to minimize the environmental impact of the world’s extensive automotive fleet. Among them, direct injection systems, especially with the use of biofuels, such as ethanol, allow the engine to operate under lean stratified conditions through split-injection. This strategy consists to split several times the fuel injection phase, so that an injection portion can be performed at the intake stroke and the other injection portion at the compression stroke. In this case, the fuel does not mix thoroughly to the intake air, which generates a heterogeneous mixture whose lambda factor varies along the combustion chamber. The results demonstrate that the use of the split-injection technique allied to lean combustion strategy on a downsized ethanol SIDI engine present significant increase of 15.9% at lambda 1.4 in overall efficiency compared to the homogeneous stoichiometric mixture condition, maintaining acceptable levels of cyclic variability. The pollutant emissions show the reduction of NO_X formation due to the lower gas temperature into the combustion chamber. The HC emission levels grow with the use of split-injection due to in-cylinder impingement. The excess of air provides a reduction on the CO₂ emission levels due to the fuel consumption reduction. In this way, the split-injection technique allied to lean combustion strategy show up as an effective tool in reducing the engine specific fuel consumption and pollutant emissions.