The Time-Variant Aerodynamic Response of a Stator Row Including the Effects of Airfoil Camber

Abstract

An experimental investigation was conducted to quantitatively determine the validity and applicability of state-of-the-art transverse gust cascade analyses. This was accomplished by obtaining fundamental time-variant forced response data at realistic values of key parameters in a large-scale, low-speed, single-stage research compressor. The forcing function, the velocity defect created by the rotor blade wakes, was measured with a crossed hot-wire probe. The resulting time-variant aerodynamic response was measured by means of flush mounted high response pressure transducers on both flat plate and cambered airfoil stator vane rows over a wide range of incidence angles. These dynamic data were then analyzed to determine the chordwise variation of the unsteady pressure difference in terms of a dimensionless dynamic pressure coefficient and an aerodynamic phase lag referenced to a transverse gust at the leading edge of the vanes. These dimensionless pressure difference data were all correlated with predictions obtained from a state-of-the-art compressible transverse gust, flat plate cascade analysis. Correlation of the classical flat plate unsteady data with the predictions permitted the range of validity of the analysis to be assessed in terms of incidence angle. Correlation of the cambered vane unsteady data with those for the flat plate and with the predictions allowed the effects of airfoil camber as well as the applicability of the flat plate prediction to realistic cambered airfoils to be quantitatively determined.

On the Prediction of Unsteady Forces on Gas-Turbine Blades: Part 1 — Typical Results and Potential-Flow-Interaction Effects

“…The unsteadiness due to the potential-flow disturbance acts over approximately 30 percent of the rotor axial chord. This explains the conclusions of Fleeter et al (1978, 1979), and Capece et al (1985, who for small values of R observed that the unsteady-pressure disturbances in multi-stage compressor cascades dominate in the front part of the cascades.…”

Rotor Blade Unsteady Aerodynamic Gust Response to Inlet Guide Vane Wakes

“…This linear chordwise distribution indicates the existence of a wave phenomenon, with a convective velocity equal to the mean axial velocity through the blade row (20.5 m/sec). This mean axial velocity wave phenomenon has been experimentally detected by other authors, Fleeter, et al (1980) and Hodson (1984) but is yet to be physically explained.…”

“…Unsteady aerodynamic gust experiments of direct interest to turbomachines have been performed in low speed research compressors. Fleeter, Jay and Bennett (1978) and Fleeter, Bennett and Jay (1980) investigated the effects of airfoil camber and rotor-stator axial spacing on the unsteady aerodynamics of a stator vane row of a single stage low speed research compressor. Capece, Manwaring and Fleeter (1986) and Capece and Fleeter (1987) performed measurements in a three stage low speed research compressor to investigate the effect of steady airfoil loading and detailed aerodynamic forcing function waveshape on the unsteady aerodynamic response of a stator vane row.…”