Turbine Secondary Flow Response to Upstream Periodic Unsteadiness

Document Type

Article

Publication Date

2020

Find this in a Library

Catalog Record

Abstract

Front-loaded turbine blades produce a strengthened secondary flow consisting of three-dimensional vortical structures contributing to increased pressure loss in the endwall region. Most studies providing a description of the secondary flow including those that sought to mitigate endwall losses using flow control have been performed in a steady environment. However, the turbomachinery flow environment is inherently unsteady mostly due to wake passing resulting from the relative motion of stators and rotors. These unsteady disturbances can affect boundary layer transition, loss generation, and the secondary flow. A novel approach to generate periodic unsteadiness using stationary pneumatic devices was implemented in a turbine blade linear cascade wind tunnel. Pulsed jets from the device generated periodic disturbances characterized by velocity deficit, increased turbulence, and spanwise vorticity. An upstream array of devices produced disturbances at varying frequencies which impinged on the lead-edge horseshoe vortex system from which the passage vortex originates. High-speed SPIV was performed in-passage to study the passage vortex dynamics. The vortex rotational strength decreased and movement increased with increased perturbation frequency. Fourier analyses found the passage vortex to be responsive at the actuation frequency and its harmonics. Phase-locked ensemble averaged results revealed that the vortex periodically varied in strength and position. The degree of which depended on the perturbation frequency. At the frequencies considered, the vortex dynamics did not lock-on and were defined by an erratic time-varying character similar to without disturbances.

DOI

10.2514/6.2020-0834

Link to Full Text

Catalog Record

Share

COinS