Sr. Manwaring et al., INLET DISTORTION GENERATED FORCED RESPONSE OF A LOW-ASPECT-RATIO TRANSONIC FAN, Journal of turbomachinery, 119(4), 1997, pp. 665-676
This paper describes a portion of an experimental and computational pr
ogram (ADLARF), which incorporates, for the first time, measurements o
f all aspects of the forced response of an airfoil row, i.e., the flow
defect, the unsteady pressure loadings, and the vibratory response. T
he purpose of this portion was to extend the knowledge of the unsteady
aerodynamics associated with a law-aspect-ratio transonic fan where t
he pow defects were generated by inlet distortions. Measurements of sc
reen distortion patterns were obtained with total pressure rakes and c
asing static pressures. The unsteady pressure loadings on the blade we
re determined from high response pressure transducers. The resulting b
lade vibrations were measured with strain gages. The steady flow was a
nalyzed using a three-dimensional Navier-Stokes solver while the unste
ady flow was determined with a quasi-three-dimensional linearized Eule
r solver. Experimental results showed that the distortions had strong
vortical, moderate entropic, and weak acoustic parts. The three-dimens
ional Navier-Stokes analyses showed that the steady flow is predominan
tly two-dimensional, with radially outward flow existing only in the b
lade surface boundary layers downstream of shocks and in the aft part
of the suction surface. At near resonance conditions, the strain gage
data showed blade-to-blade motion variations and thus, linearized unst
eady Euler solutions showed poorer agreement with the unsteady loading
data than comparisons at off-resonance speeds. Data analysis showed t
hat entropic waves generated unsteady loadings comparable to vortical
waves in the blade regions where shacks existed.