Effects of primary swirl intensity on flow and fuel distribution downstream a dual-swirl cup

In order to improve the ignition performance of dual-swirl cup, the downstream flowfield and fuel distribution should be optimized. The flowfield and fuel distribution downstream a baseline dual-swirl cup were measured by Particle Dynamics Analyzer (PDA). Based on the results, an improved dual-swirl cup scheme was proposed with only 6.7% increase of swirl number and 44% decrease of tangential momentum moment for the primary swirl, and the flowfield and fuel distribution were measured and compared with the baseline one. The experimental results indicate that the reduced tangential momentum moment of the primary swirl will affect the flowfield downstream the dual-swirl cup, and then change the flowfield structure from converge-diverge type to diverge one and decrease the Sauter Mean Diameter (SMD) of the fuel spray. When the distance downstream the swirl cup reaches 2.5 times the venturi throat diameter, the effect of flowfield transportation and droplet evaporation could be enhanced to make fuel distribution more uniform and SMD smaller. Both the swirl number and tangential momentum moment of swirlers should be considered in dual-swirl cup design for aeroengine combustor.