Experimental investigation on liquid breakup regimes and spray characteristics in slinger atomizers with various injection orifices

Slinger atomizers, known as one type of rotary atomizers, have been widely applied in various small gas turbine engines. The fuel can be well atomized by taking advantage of the high rotational speed of the turbine shaft. The geometric characteristics of the injection orifice play an important role in determining the atomization performance of the slingers. The breakup regimes and the droplet size of the slinger atomizers with slot-shaped orifices have rarely reported in the past. Herein, three types of slinger atomizers with different orifice shapes and orifice diameters are tested at rotational speeds of 8000-20 000 rpm and liquid feed rates of 4 up to 20 g/s. High-speed shadowgraph imaging, high-speed digital imaging, and planar Mie technologies are applied to provide the spray breakup process, liquid film injection features, and droplet distribution, respectively. Spray visualizations show that the orifice diameters strongly affect the breakup modes, whereas the orifice shapes have a slight effect. The variation regarding droplet sizing under different heights from the slinger plane is analyzed. The uniformity of the droplet distribution in slot-shaped slinger atomizers is better than that in round-shaped slinger atomizers. Moreover, the smaller orifice diameter results in a small Sauter mean diameter (SMD) for the slinger atomizers with slot-shaped orifices. Finally, a mathematical expression is obtained to predict non-dimensional droplet size (SMD/d) for different slinger atomizers. The present results appear to be the first systematic investigation of the spray characteristics in slinger atomizers with slot-shaped orifices.