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Decreased axial spacing between blade rows in an axial compressor
stage is thought to increase stage performance because of an unsteady
process that occurs in the downstream blade row and acts on the
upstream blade row wakes. This process results in the "recovery"
of part of the wake energy before all of this energy is irreversibly
lost due to viscous diffusion. To study the wake-blade interaction
mechanism, researchers at the NASA Lewis Research Center acquired
two-component Laser Fringe Anemometer measurements of the rotor
wake in the single-stage transonic compressor at two stage loading
levels. The detailed measurements were acquired for one stator
pitch in circumference at axial positions from the rotor trailing
edge to 20 percent of the stator axial chord, at the exit of the
stator passage, and downstream of the stator row including the
stator wake. These data show that the changes in wake energy that
occur inside the stator passage are not due to viscous dissipation
alone, and thus the data provide evidence that "wake recovery"
is occurring.
A time-accurate, three-dimensional Navier Stokes simulation of
the compressor stator was done at the corresponding stage loading
levels. The measurements and simulations are being used in combination
to show the effects of stator blade loading, quantify the effects
of viscosity, and quantify the stage efficiency gain due to the
wake recovery process. The accuracy of simple models of the wake
recovery process is being evaluated in an effort to include the
effects of wake recovery in the NASA-developed Average Passage
code for multistage turbomachinery simulations.
Previous articleLast updated April 29, 1997
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