Results from a numerical simulation of the unsteady flow
through one quarter of the circumference of a transonic
high-pressure turbine stage, transition duct, and low-pressure
turbine first vane are presented and compared with
experimental data. Analysis of the unsteady pressure field resulting
from the simulation shows the effects of not only the
rotor/stator interaction of the high-pressure turbine stage
but also new details of the interaction between the blade and
the downstream transition duct and low-pressure turbine
vane. Blade trailing edge shocks propagate downstream,
strike, and reflect off of the transition duct hub and/or downstream
vane leading to high unsteady pressure on these
downstreamcomponents. The reflection of these shocks from the downstream components back into the blade itself has
also been found to increase the level of unsteady pressure
fluctuations on the uncovered portion of the blade suction
surface. In addition, the blade tip vortex has been found to
have a moderately strong interaction with the downstream
vane even with the considerable axial spacing between the
two blade-rows. Fourier decomposition of the unsteady surface
pressure of the blade and downstream low-pressure turbine
vane shows the magnitude of the various frequencies
contributing to the unsteady loads. Detailed comparisons
between the computed unsteady surface pressure spectrum
and the experimental data are shown along with a discussion
of the various interaction mechanisms between the blade,
transition duct, and downstream vane. These comparisons
show-overall good agreement between the simulation and experimental
data and identify areas where further improvements
in modeling are needed.