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The effects of air flow forcing on fuel spray characteristics in a premixing swirler were assessed using ambient-pressure experiments and CFD (LES) analyses. Experimental measurements were performed using phase-locked Phase-Doppler Interferometry on two different swirler/mixer designs. The CFD analyses employed an advanced spray modeling technique to track the surface of the liquid fuel. The swirler designs chosen were representative of advanced low-emissions combustor concepts that emphasize thorough fuel/air mixing for Jet-A fuel. Significant post-processing of the results was performed in order to extract the response of the fuel spray mass flow rate fluctuations and fuel/air ratio to acoustic forcing. The results demonstrated that i) acoustic air forcing did not significantly change the atomization process, but did influence the unsteady transport of fuel droplets within the swirler flow field, ii) the level of fuel mass flow fluctuation was higher for one swirler and the level of fuel/air ratio fluctuations was higher for the other swirler and iii) the different behaviors between the two swirlers are primarily caused by the discrepant alignment of fuel and air distribution and the dissimilar droplet Stokes number which governs the unsteady transport. CFD results were interrogated to help understand the root causes of the observed phenomena. These showed that, for the swirler in which fuel mass flow fluctuations were observed, the swirl number was modulated by the acoustic forcing.

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