Abstract: In this paper, the effect of ambient pressure on the morphological characteristics of a multi-hole gasoline direct injection (GDI) spray is simulated in CONVERGE. Firstly, a constant volume vessel spray model is established based on the injector parameters. According to the test results of high-speed imaging and phase doppler particle analyzer (PDPA), the Sauter Mean Diameter (SMD), spray morphology and penetration distance of the model is verified. Based on this, a detailed study on the spray morphological characteristics under 0.1,0.5 and 1MPa ambient pressure conditions is conducted. The results show that, the spray is compressed and contracted to the central axis of the injector and the penetration distance decreases under elevated ambient pressure. Due to the impact of the spray on the airflow in the vessel, a strong air entrainment effect is generated on the outer edge of the spray, resulting in rolling upward of the droplet at the end of the spray with the gas flow, and the higher the back pressure, the more indistinct the boundary of the spray end. After analysis of the spray pressure field and velocity field, it is found that pressure of the inner zone of the spray is lower than the outer zone, which causes the external airflow to impact the spray, thus reducing the spray width and enhancing the interaction, resulting in spray collapse

Key words: GDI spray, ambient pressure, spray collapse, 3D simulation