Vane Swirler Performance

Swirler performance characteristics are investigated under low speed, low turbulence intensity conditions so as to aid in computer modeling of flowfields, and in the development and evaluation of turbulence models for swirling confined flow. The swirler studied is annular with a hub-to-swirler diameter ratio of 0.25 and ten adjustable vanes of pitch-to-chord ratio 0.68. Measurements of time-mean axial, radial, and swirl velocities are made at the swirler exit plane using a five-hole pitot probe technique with computer data reduction. A theoretical study is included of idealized exit-plane velocity profiles relating the swirl numbers S and S′ to the ratio of maximum swirl and axial velocities for each idealized case. The time-mean velocity components measured at the swirler exit plane show clearly the effects of centrifugal forces, recirculation zones, and blade wakes on the exit-plane velocity profiles. Assumptions of flat axial and swirl profiles are found to be progressively less realistic as the swirl vane angle increases, with axial and swirl velocities peaking strongly at the outer edges of the swirler exit and significant non-zero radial velocities present. Nonaxisymmetry is present in all swirl cases investigated.