LDV Measurements of Unsteady Flow in a Turbine Rotor

Abstract

V2 time-averaged and mass-averaged relative velocity at rotor exit plane (plane 44, axial distance ZRT / Cax,RT = 1.459) The unsteady flow field in an axial-flow turbine rotor under low Reynolds number condition (Reout,RT = 3.60×10) was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-dependent unsteady distributions of velocity, flow angle, turbulence intensity and Reynolds stress were carried out at design operating condition. The obtained data was analyzed in terms of both absolute (stationary) frame of reference and relative (rotating) frame of reference. The effect of stator wake and secondary vortices on the flow field inside the rotor passage was clearly determined. X pitch-wise distance ZRT axial distance from rotor leading edge ZST axial distance from stator leading edge θ flow angle measured from axial direction vx’vz’ velocity correlation (Reynolds stress) Subscripts Abs absolute flow or absolute frame of reference in stator or rotor inlet value out stator or rotor outlet value Rel relative flow or relative frame of reference RT rotor value ST stator value Nomenclature Introduction Cax axial chord length With the new generation of small-sized gas turbine engines, low Reynolds number flows have become increasingly important. Blade Reynolds numbers for the turbine stage of small-sized gas turbines can drop below 10. At these low Reynolds number conditions, the boundary layer is dominated by laminar flow and is susceptible to flow separation, which is associated with increased loss and reduced performance. Recently, a lot of studies focused on the characteristics of turbine Re Reynolds number t time TRT rotor passing period in absolute frame TST stator passing period in relative frame Tu turbulence intensity V velocity V1 time-averaged and mass-averaged absolute velocity at stator exit plane (plane 1, axial distance ZST / Cax,ST = 1.075) 1 American Institute of Aeronaut 32nd AIAA Fluid Dynamics Conference and Exhibit 24-26 June 2002, St. Louis, Missouri AIAA 2002-2742 Copyright © 2002 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Test Section