Abstract:

The current research on the dual-stage swirl airblast atomizer is primarily experimental and cannot explain the atomization mechanism and evolution process. To master the fuel mixing and distribution characteristics of the dual-stage swirl airblast atomizer， and clarify the atomization mechanism of fuel jets under different combustion chamber inflow conditions， RANS turbulence model coupled with VOF and VOF-to-DPM model were adopted in this paper. Combined with adaptive grid technology， the numerical simulation of primary atomization in the whole fluid domain， including fuel fluid domain and air fluid domain， was carried out. The process of liquid film formation on the pressure swirl atomizer and the wall of the Venturi tube and the process of breaking into filaments and droplets were successfully captured in the results. Compared with the experimental results， the maximum error of spray angle is only 1.34%， and the breakup length of liquid film at the outlet is consistently 0.8 mm， which verifies the correctness of the simulation results. The atomization characteristics of the pressure swirl atomizer with and without swirling air were compared and analyzed. It was found that the primary swirling air will cause periodic oscillation of liquid film at the outlet of the pressure swirl atomizer which can increase the spray angle and shorten the breakup length. However， it also increases the liquid film thickness， thereby reducing the velocity of liquid film at the outlet of the pressure swirl atomizer. The effects of air pressure drop， inlet pressure and temperature， and fuel flow rate on spray angle and Sauter Mean Diameter （SMD） of the dual-stage swirl airblast atomizer were analyzed. The results show that as the air pressure drop across the swirler increases， the spray angle increases， and SMD decreases. As the inlet pressure and temperature increase， the spray angle increases and then tends to balance， and SMD decreases first， then increases and finally decreases. Additionally， as the fuel flow rate increases， the spray angle increases first and then decreases， and SMD shows a decreasing trend. In this paper， the numerical simulation of the dual-stage swirl airblast atomizer in the whole fluid domain is developed， providing theoretical support for a better understanding of the evolution process and atomization mechanism of this type of atomizer.

Key words: dual-stage swirl airblast atomizer, fuel evolution, primary atomization, whole fluid domain, atomization characteristics