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The atomization process of swirling sprays in gas turbine engines has been investigated using a LES-VOF model. With fine grid resolution, the ligament and droplet formation processes are captured in detail. The spray structure of fully developed sprays and the flow field are observed firstly. A central recirculation zone is generated inside the hollow cone section due to the entrainment of air by the liquid sheet and strong turbulent structures promote the breakup of ligaments. At the exit of injector nozzle, surface instability occurs due to disturbance factors. Axial and transverse mode instabilities produce a net-like structure ligament zone. Finally, the generation mechanism of the droplet is analyzed. It is found that the breakup mechanism of ligaments is located at the Raleigh capillary region. Axial symmetry oscillation occurs due to the surface tension force and the capillary waves pinch off from the neck of the ligaments. Secondary breakup and coalescence occur at the “droplet zone,” resulting in a wider distribution curve at the downstream area. [ABSTRACT FROM AUTHOR]

The phenomenon of shock waves can be commonly seen in fuel spray under ultra-high injection pressure conditions, where the spray jet penetrates at speeds greater than Mach 1. This paper focuses on the induction of shock waves and their propagation characteristics generated by a supersonic fuel jet at 400 MPa, and simultaneously considers the impact of jet atomization. A specially designed atomizer, utilizing diaphragm rupture, was adopted to replace the traditional electronic valves fuel system to meet the ultra-high injection pressure. Visualization of the spray field by using a high-speed camera was conducted, and a Schlieren apparatus was equipped for shock capturing based on a variable environmental density distribution. The experimental results indicated that the leading edge shock wave shows two forms in the early stage, and each penetrates in a unique way. Along with the spray development, multiple expansion waves were sequentially generated, followed by the leading shock wave. The evolution of wave velocity over time was calculated from the penetration results, and the results showed that the velocity first increased rapidly and then slowly decreased as a result of the effect of air resistance, with a gradual tendency of decreasing for the four peak velocities of the intensity weakened waves. In addition, the spray convex flow path had an inhibitive effect on the deceleration of the first expansion wave. These results give an insight into diesel spray and propagation process of induced shock waves at an under ultra-high injection pressure of 400 MPa. [ABSTRACT FROM AUTHOR]