Affiliations: Department of Mechanical Engineering, Saga University,
1 Honjo-machi, Saga 840-8502, Japan.
Abstract: An Unsteady flow field with rotating stall cells in a high
specific-speed diagonal flow fan has been investigated experimentally. Although
a general feature of stall cells has already indicated, i.e., the number of
stall cells is one and its propagating speed is approximately 80 percent of
rotor speed, little has been known about the flow field when a rotating stall
occurs because of its unsteadiness. In order to capture the behavior of the
rotating stall cell, measurements of the flow field at the rotor inlet were
carried out with a single slant hot-wire. Those data were processed by a
so-called "double phase-locked averaging" (DPLA) technique, which enabled to
capture the flow field of the cell in the reference co-ordinate system fixed to
the rotor. As a result, time-dependent ensemble averages of the
three-dimensional velocity components at the rotor inlet have been obtained and
the behavior of the rotating stall cell has been illustrated with each velocity
component.
Keywords: turbomachinery, rotating stall cell, unsteady flow, DPLA technique, fan