Investigation of flow characteristics and breakup mechanism in a multi-orifice slinger atomizer under open-condition operation

To investigate the flow characteristics and atomization properties of a multi-orifice (N = 24) slinger atomizer, this paper utilizes a combined numerical–experimental approach to examine the internal fuel flow and injection processes under operational conditions spanning rotational speeds of 0–20 000 rpm and fuel flow rates of 10–50 g/s. This work provides the first detailed analysis of the Coriolis-driven “crescent” film formation inside the orifice, establishing a quantitative link between the internal film dynamics and the external primary breakup modes, which governs the resultant droplet size distribution. Both the jet injection and breakup processes are studied via a high-speed camera and image processing methods, accompanied by numerical simulation of fuel flow within the slinger for auxiliary analysis. The results indicate that there is a liquid film at the top of the collection chamber. Inside the orifice, influenced by Coriolis force, the liquid film deflects and accumulates in a “crescent” shape on one side of the orifice. In addition, the radial velocity Ub and resultant velocity U of the liquid film are determined. It is observed that both of them exhibit a linear correlation with the rotational speed, increasing as the rotational speed increases. Moreover, the study finds that the Rossby number and the liquid Weber number determine the jet injection pattern at the orifice (liquid column, liquid sheet, and mist). Based on different injection patterns, five jet breakup modes are observed from the flow visualization, including Rayleigh, Sheet, Bag, stretched ligament, and shear breakup modes. For further assessment of the atomization quality, a DP-02 laser particle size analyzer is employed to measure the droplet sizes. The results indicate that there is a strong correlation between Sauter mean diameter (SMD) and the aerodynamic Weber number (Wed), as well as the liquid-to-gas momentum ratio q. Furthermore, the SMD for this slinger at 20 000 rpm are consistently below 25 μm, which is more compatible for the ignition condition of the slinger-type gas turbine combustor.