Aerodynamics of a low-pressure turbine airfoil at low Reynolds numbers-Part I: Steady flow measurements

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Journal titleJournal of Turbomachinery
Article number11015
SubjectChord lengths; Experimental investigations; Freestream turbulence; Freestream turbulence intensity; Hot-film measurement; Inflow conditions; Laminar separations; Length scale; Linear cascade; Low Reynolds number; Low-pressure turbines; ON dynamics; Reynolds; Separated flows; Separation bubble; Statistical properties; Suction side; Suction surfaces; Transition phenomenon; Transition process; Turbulence intensity; Aerodynamics; Airfoils; Boundary layer flow; Turbines; Reynolds number
AbstractThis two-part paper presents a detailed experimental investigation of the laminar separation and transition phenomena on the suction surface of a high-lift low-pressure turbine airfoil, PakB. The first part describes the influence of Reynolds number, freestream turbulence intensity and turbulence length scale on the PakB airfoil under steady inflow conditions. The present measurements are distinctive in that a closely-spaced array of hot-film sensors has allowed a very detailed examination of the suction surface boundary layer behavior. In addition, this paper presents a technique for interpreting the transition process in steady, and periodically unsteady, separated flows based on dynamic and statistical properties of the hot-film measurements. Measurements were made in a low-speed linear cascade facility at Reynolds numbers between 25,000 and 150,000 at three freestream turbulence intensity levels of 0.4%, 2%, and 4%. Two separate grids were used to generate turbulence intensity of 4% with integral length scales of about 10% and 40% of the airfoil axial chord length. While the higher levels of turbulence intensity promoted earlier transition and a shorter separation bubble, turbulence length scale did not have a noticeable effect on the transition process. The size of the suction side separation bubble increased with decreasing Reynolds number, and under low freestream turbulence levels the bubble failed to reattach at low Reynolds numbers. As expected, the losses increased with the length of the separation bubble, and increased significantly when the bubble failed to reattach. © 2013 American Society of Mechanical Engineers.
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AffiliationNational Research Council Canada (NRC-CNRC); Aerospace (AERO-AERO)
Peer reviewedYes
NPARC number21269232
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Record identifierf2acc973-5c96-4c62-8216-7d3e21eebcfe
Record created2013-12-12
Record modified2016-05-09
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