Handbook of Turbomachinery Second Edition Revised - Ventech!

lades, the wavelength of the disturbance is the whole circumference. As will
be discussed later, disturbances with long circumferential length scales can
have marked effects on downstream blade rows.
So far, most of clocking studies have been carried out for stators, e.g.,
the experimental work for a low-speed compressor by Barankiewicz and
Hathaway [8]. Rotor–rotor interactions (clocking and aperiodicity) might,
however, behave differently in particular when a downstream rotor row is
transonic. A relevant mechanism to be taken into consideration is that
associated with the passage shock wave of rotor-2 interacting with the wake
shed from rotor-1. The mixing loss of a wake would be higher when the
wake is subject to an adverse pressure gradient [9]. Thus, in this transonic
‘‘mean’’ flow condition, the mixing loss of rotor-1 wake is certainly expected
to rise when passing through the rotor-2 passage shock wave, as shown by
the schematic in Fig. 5. Given that the strength of the rotor passage shock
varies pitchwise (typically stronger near the suction side), it would not be
surprising that the rotor–rotor interaction loss is dependent on the clocking
position.
In contrast to typical flow conditions for transonic rotors, the ‘‘mean’’
flow in which two stator rows interact is subsonic. Therefore, it seems
reasonable to expect more pronounced rotor–rotor interference (aperidoic
Figure 5 Rotor-1 wakes crossing rotor-2 passage shock at two different clocking
positions.
Copyright © 2003 Marcel Dekker, Inc.