关键词: 闪急沸腾雾化，高压喷射，内燃机，光学诊断

Abstract: The increasingly stringent emission regulations and fuel consumption requirements have elevated the demands of internal combustion engines with higher fuel efficiency and lower emissions. It has been widely demonstrated that flash boiling spray can generate shorter and wider spray with improved atomization and evaporation to promote a better air-fuel mixing process. In this study, macroscopic (far-field) spray morphologies and primary breakup (near-field) characteristics of a two-hole gasoline direct injection injector are investigated under non-flash boiling and flash boiling conditions. High speed macroscopic and microscopic imaging was used to capture the overall spray structure and near-field characteristics, respectively. N-Hexane is used as the test fuel with the injection pressure ranging from 10 MPa up to 40 MPa. For sub-cooled liquid fuel sprays, increasing fuel pressure contributes to enhanced fuel atomization and evaporation. Evident collapses occurred under flare flash boiling conditions, and higher injection pressure weakened this phenomenon since the spray cone angle decreased due to a higher injection velocity.

Key words: flash boiling atomization, high-pressure injection, internal combustion engines, optical diagnostics