The effects of circumferential distortions in inlet total pressure on
the flow field in a low-aspect-ratio, high-speed, high-pressure-ratio,
transonic compressor rotor are investigated in this paper. The flow f
ield was studied experimentally and numerically with and without inlet
total pressure distortion. Total pressure distortion was created by s
creens mounted upstream from the rotor inlet. Circumferential distorti
ons of eight periods per revolution were investigated at two different
rotor speeds. The unsteady blade surface pressures were measured with
miniature pressure transducers mounted in the blade. The flow fields
with and without inlet total pressure distortion were analyzed numeric
ally by solving steady and unsteady forms of the Reynolds-averaged Nav
ier-Stokes equations. Steady three-dimensional viscous flow calculatio
ns were performed for the flow without inlet distortion while unsteady
three-dimensional viscous flow calculations were used for the flow wi
th inlet distortion. For the time-accurate calculation, circumferentia
l and radial variations of the inlet total pressure were used as a tim
e-dependent inflow boundary condition. A second-order implicit scheme
was used for the time integration. The experimental measurements and t
he numerical analysis are highly complementary for this study because
of the extreme complexity of the flow field. The current investigation
shows that inlet flow distortions travel through the rotor blade pass
age and are convected into the following stator. At a high rotor speed
where the flow is transonic, the passage shock was found to oscillate
by as much as 20 percent of the blade chord, and very strong interact
ions between the unsteady passage shock and the blade boundary layer w
ere observed. This interaction increases the effective blockage of the
passage, resulting in an increased aerodynamic loss and a reduced sta
ll margin. The strong interaction between the passage shock and the bl
ade boundary layer increases the peak aerodynamic loss by about one pe
rcent.