Flows In Rotating Diffusers : Effects of Diffuser Angle

Abstract

The flow patterns and pressure recoveries in rotating, conical diffusers were investigated experimentally. The conical diffusers have straight walls and opening angles of 7°, 10°, 15°, respectively. Even in a diffuser having no separated zone in a stationary state such as in the case of diffusers with an opening angle equal to or less than 10°, separations occur on the lower pressure wall when the diffusers are rotated at a speed exceeding a certain limit. Velocity profiles and pressure distributions as well as the flow separation in diffuser sections are governed by a parameter defined by the ratio of a rotational Reynolds number to a flow Reynolds number. As the rotation rate increases, the point of separation approaches the inlet section of the diffuser and wakes formed by this separation grow in size, resulting in a poor pressure recovery in the diffuser. At the same rate of rotation, the pressure recovery in the diffuser with an opening angle 10° was the best of the diffusers tested.