Characteristics of the recirculation zone downstream a dual-swirl cup at varied inlet Reynolds numbers

To analyze the role of the flow structure downstream the swirl cup on the performance of aero gas turbine combustors, PIV (particle image velocimetry) was used to measure the non-reacting flow field downstream a dual-swirl cup under ambient pressure and temperature, and the effect of the inlet Reynolds number on the recirculation zone downstream a dual-swirl cup was studied. The experimental results indicate that the flow structure downstream is a converge-diverge type when the inlet Reynolds number is low. As the inlet Reynolds number increases to 25 000, the flow structure turns to a diverge type. Then the flow structure of recirculation zone remains unchanged with increasing inlet Reynolds number, but the normalized velocities in the recirculation zone would increase accordingly.