Sl. Puterbaugh et Ww. Copenhaver, FLOW-FIELD UNSTEADINESS IN THE TIP REGION OF A TRANSONIC COMPRESSOR ROTOR, Journal of fluids engineering, 119(1), 1997, pp. 122-128
An experimental investigation concerning tip flow field unsteadiness w
as performed for a high-performance, state-of-the-art transonic compre
ssor rotor. Casing-mounted high frequency response pressure transducer
s were used to indicate both the ensemble averaged and time varying fl
ow structure present in the tip region of the rotor at four different
operating points at design speed. The ensemble averaged information re
vealed the shock structure as it evolved from a dual shock system at o
pen throttle to an attached shock at peak efficiency to a detached ori
entation at near stall. Steady three-dimensional Navier Stokes analysi
s reveals the dominant flow structures in the tip region in support of
the ensemble averaged measurements. A tip leakage vortex is evident a
t all operating points as regions of low static pressure and appears i
n the same location as the vortex found in the numerical solution. An
unsteadiness parameter was calculated to quantify the unsteadiness in
the tip cascade plane. In general, regions of peak unsteadiness appear
near shocks and in the area interpreted as the shock-tip leakage vort
ex interaction. Local peaks of unsteadiness appear in mid-passage down
stream of the shock-vortex interaction. Flow field features not eviden
t in the ensemble averaged delta are examined via a Navier-Stokes solu
tion obtained at the near stall operating point.