Laser Doppler velocimetry investigation of swirler flowfields

Detailed measurements of mean and turbulent velocity components and turbulent shear stress components have been made for jet flows of 20-, 40-, and 60-deg swirlers for 750 and 1500 mm H2O supply air pressure conditions. When the mean velocity components are normalized based on the maximum axial velocity at the nozzle exit, there is a very close similarity between normalized profiles at different supply pressures for each swirler. The recirculation zone, which depends on the degree of swirl and the swirler geometry, is not well established near the nozzle exit for the case of high ratio of the inner to outer radius of the swirler and of low degree of swirl. This can create a serious deposition problem of fuel droplets onto the hub surface. Measurements of turbulent velocity components demonstrate that each jet can be considered to be close to local isotropic turbulence except at the nozzle exit, where the magnitudes and decay of the fluctuations depend strongly on flow direction. (C.D.)