Split injection in a homogeneous stratified gasoline direct injection engine for high combustion efficiency and low pollutants emission

The definition of the control strategy leading to the greatest combustion efficiency and lowest pollutants emission is made in two steps through numerical optimization: the 3D CFD model is first run to build a low number of samples to be used within a Gaussian RSM (response surface method) to reconstruct, in the DOE (design of experiments) space, the integral of the in-cylinder pressure over volume in the closed valve period; in the second step, the coupling between the 3D engine model and the Simplex algorithm is performed in a restricted DOE subdomain defined according to the first step analysis. The assessed methodology highlights the synchronization of both spark ignition and split injection leading to the highest power output and the lowest pollutants release. The experimental verification of the numerical findings is finally carried out.