Handbook of Turbomachinery Second Edition Revised - Ventech!

Figure 12 Calculated instantaneous entropy contours for two-stage turbine at
partial admission.
admission is less than half of that for the 1650% admission. Therefore, we
see that the nonuniformity with a longer circumferential wavelength decays
at a much slower rate in the axial direction.
The second example concerns responses of a blade row to inlet
distortions. In this case, stationary stagnation pressure distortions are
specified at the inlet to a transonic fan rotor row. And the results obtained at
the same distortion amplitude of 15% are compared for two different
circumferential wavelengths [19]. The distortion pattern in the first case has
11 nodal diameters (wavelength ¼ 2 passages). In the second case, the
distortion has 1 nodal diameter (wavelength ¼ whole annulus, 22 passages).
The influence of the circumferential distortion wavelength can probably be
best illustrated by time-space static pressure contours on the suction surface
at 90% span, as shown in Fig. 14. Note that at this spanwise section, the
passage shock wave in a steady solution is situated on the suction surface
around 85–90% chord. The results demonstrate that the passage shock
oscillation is strongly dependent on the distortion wavelength. For the short
wavelength case [Fig. 14(a)] the shock oscillation is confined to 3–5% chord,
Copyright © 2003 Marcel Dekker, Inc.