Schlieren and mie scattering techniques for the ECN “spray G” characterization and 3D CFD model validation

The beneficial impact of direct injection strategy (DI) on spark ignition (SI) engine performances is largely recognized in terms of fuel economy and emissions reduction [1]. DISI engines operate at higher compression ratios with respect to port fuel injection (PFI) ones, resulting in higher thermal efficiencies and power outputs. Moreover, different injection strategies can be chosen, so the greater control over the air-to-fuel ratio allows operating under lean fuel conditions, in the stratified charge mode, approaching the efficiencies and emission indexes of compression ignition engines. On the other hand, today engines strongly differ from yesterday ones, due to their complexity and high number of sub-systems, so that traditional tools and techniques used for their design are often insufficient for the required challenges of high power output and low environmental impact. In this change of perspective, from a test-first culture to an analysis-led design process, numerical simulation tools, as CFD (computational fluid dynamics) models, are becoming increasingly important to accelerate the time to market of high-efficiency clean power units for transportation [2]. Present work aims at giving a contribution to the validation of 3D CFD models for the simulation of the in-cylinder thermo-fluidynamic processes underlying energy conversion, in particular by giving a detailed experimental insight into the dynamics and impact over walls of multi-hole sprays for DISI applications through combined schlieren and Mie scattering techniques.