Abstract: Experiments were performed to investigate the flow structures of humid air combustion flame in a multihole nozzle swirl burner. The experiments show that with steam addition, the flame becomes dark, and the flame dimensions grow; the distances between vortexes of recirculation zone and nozzle reduce; the peaks of radial mean velocity, radial rms velocity and Reynolds shear stress decrease; the maximum mean turbulent kinetic energy decreases, and the biggest reversing velocity on nozzle centerline reduces; the width of recirculation zone and the distance between centerline biggest reversing velocity and nozzle is lower; the expansion angle of swirling jet reduces；the axial nonuniform coefficient of outlet increases.

Key words: swirling combustion, humid air combustion, PIV measurement