Study on the atomization and mixing process of elliptical nozzle under the spatial constraint of combustion chamber

In this paper, numerical simulations are conducted to investigate the atomization and mixing processes of elliptical nozzles under the spatial confinement of a diesel engine combustion chamber. This study aims to address the critical requirements for improving fuel atomization performance and air-fuel mixing quality, which are essential for achieving high engine efficiency, energy savings, and ultra-low emissions. The results show that, compared with the circular nozzle, the elliptical nozzle has lower cavitation degree, smaller initial fuel velocity, larger spray volume, shorter penetration under the action of airflow resistance, delayed wall impingement time, higher mixing uniformity, faster fuel evaporation, and better spray atomization effect. When the rotation angle of the elliptical nozzle is 90° (E90° scheme), the initial velocity of the spray is the lowest, the penetration is the smallest, and the atomization and mixing effect of the spray is the best. The spray Sauter Mean Diameter (SMD) of E90° is 50.7% lower than that of the circular nozzle. An increased injection angle elevates the wall impingement position, advances impingement timing, and increases wall fuel film thickness, thereby deteriorating atomization performance. Conversely, a reduced injection angle delays wall impingement through enhanced flow field resistance, which promotes fuel breakup and mixing while accelerating evaporation. For instance, the E90° configuration achieves a 49% reduction in Sauter Mean Diameter (SMD) at a 73° injection angle.