Author: Kaushik Saha (Indian Institute of Technology Delhi) - The Gasoline Direct Injection (GDI) system represents an advanced technology that enables engines to operate at higher compression ratios, thereby achieving greater volumetric efficiency compared to Port Fuel Injection (PFI) engines. A crucial factor affecting the performance of GDI engines is the atomization of the fuel spray, which is vital for efficient combustion. GDI systems generally operate at higher injection pressures than their PFI counterparts, resulting in improved spray atomization, finer droplets, faster vaporization, and enhanced air-fuel mixing. Notably, GDI systems demonstrate superior fuel spray atomization under flash boiling conditions— a non-equilibrium phenomenon that occurs in GDI engines during part-load and idle operations. This study explores a newly developed simplified flash boiling vaporization model, and a spray breakup methodology tailored for flashing conditions. These methodologies were implemented using User-Defined Functions (UDFs), allowing for adjustments to model constants and the overall modeling approach based on variations in the surrounding conditions of the spray. The research utilized the Spray G injector from the Engine Combustion Network (ECN). The impact of the developed models and proposed breakup methodology in a GDI engine were evaluated under two operating modes: homogeneous and stratified. The findings demonstrate that implementing the developed model significantly enhances spray breakup and vaporization under flashing conditions, which helps in achieving the better combustion performance and emissions.
