Secondary Flow Mixing Losses in a Centrifugal Impeller
Detailed flow measurements made in a 1-m dia shrouded centrifugal impeller running at 500 rpm are presented. All three mutually perpendicular components of relative velocity and rotary stagnation pressures were measured on five cross-sectional planes between the inlet and the outlet, using probes which were traversed within the rotating impeller passage. The reduced static pressures were also calculated from these flow measurements. The measurements were made for an impeller flow rate corresponding to approximately zero incidence at the blade leading edges. Shroud boundary layer separation and secondary flow were observed to lead to the formation of a wake in the suction-side/shroud corner region. It is concluded that the turbulent mixing associated with the shroud boundary layer separation and the strength of the secondary flow strongly influence the size and location of the wake, respectively.