A three-dimensional compressible flow model is presented to study the occurrence of weak rotating waves in vaneless diffusers of centrifugal compressors. The diffuser considered has two parallel walls, and the undisturbed flow is assumed to be circumferentially uniform, isentropic and to have no axial velocity. Linearised 3D compressible Euler eqns. were casted on a rotating coordinate system traveling at the same angular speed as the wave cells. A disturbance of radial velocity at the inlet and a uniform static pressure at the outlet of the diffuser were imposed. Complex functions of the solutions to the eqns. were obtained by a second order finite difference method and the Singular Value Decomposition technique. The influences of the inlet Mach number on the rotating waves were studied and preliminary results show that the critical flow angle and rotating wave speed are both affected by the Mach number. However, the angle only increases slightly with the Mach number while the wave speed increases rapidly with the Mach number.

This content is only available via PDF.
You do not currently have access to this content.