(c)
Fig. 16 FFT at rotor/outlet interface at span 10% (left), 50%
(middle) and 90% (right)
In this IGV-rotor configuration the main unsteadiness is attributed to
the core of rotor wakes, and the intensity of velocity deficit in wakes
is modulated by the unmixed vanes wakes convected out in the rotor
passages. The behavior of this deterministic unsteadiness is seen to be
more important at low flow rates operation. To examine the effects of
pseudo IGV clocking, the vane was displaced at four positions. Table 6
summarizes the obtained amplitudes of pressure fluctuations at IGV/
rotor interface. As noticed the amplitude of the principal mode and its
harmonics are sensitive; for reference position and that of 4.73 deg and
18.95 deg, the potential mode and harmonics are seen the dominant,
whereas for positions of 9.47 deg and 14.21 deg, there is an emergence
of a second mode with a frequency 2200 Hz which becomes very important.
These pseudo interactions depend on the clocking angle as highlighted by
amplitudes of predominance modes.
Table 6. Pressure amplitude of main frequencies at IGV/Rotor
interface with pseudo clocking positions