Effects of structured prefilmer lip on spray characteristics in planar prefilming airblast atomization

Effective liquid fuel atomization is an ultimate aim for the prefilming airblast atomizer in aero-engines, and the liquid fuel breakup behavior is the key indicator of atomization quality. Whereas, the prefilmer lip structure is unnoticed but of great influence on this breakup process. In this paper, the rectangular block structured prefilmer lip and the triangular prism structured prefilmer lip are delicately designed and adopted in planar prefilming airblast atomization. Accordingly, the spray characteristics, including the liquid film morphology, droplet distributions, and atomization quality are comprehensively investigated under structured prefilmer lips, using a coupled LB-LES model. The numerical results reveal that when the rectangular block structured prefilmer lip is adopted, the multihole morphology appears on the liquid film under the cutting effect of the rectangular sawtooth, thus contributing to the liquid breakup process. The droplet equivalent diameter in the atomization process distributes exponentially, and 70%-80% of the droplet sizes are less than 100 μm. The droplet velocity shows a normal distribution with its average value located from 1 m/s to 2 m/s in the streamwise direction when the air velocity is 20 m/s. Ultimately, according to droplet size, droplet velocity, and atomization angle, along with the atomization efficiency coefficient, the atomization quality under the rectangular block structured prefilmer lip is better than that with triangular prism structured prefilmer lip and unstructured prefilmer lip, and the highest atomization quality is obtained with rectangular block width of 0.3 mm.