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Aerodynamic Loss Measurements in a Compressible Flow Vane Cascade Showing the Influence of Reynolds Number Lapse

[+] Author Affiliations
M. P. Mihelish

Solar Turbines, Inc., San Diego, CA

F. E. Ames

University of North Dakota, Grand Forks, ND

Paper No. GT2013-95052, pp. V06AT36A025; 10 pages
doi:10.1115/GT2013-95052
From:
  • ASME Turbo Expo 2013: Turbine Technical Conference and Exposition
  • Volume 6A: Turbomachinery
  • San Antonio, Texas, USA, June 3–7, 2013
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-5522-5
  • Copyright © 2013 by ASME

abstract

Turbofan engines are designed to operate over a range of conditions depending on the mission of the aircraft. Many unmanned aerial vehicles (UAVs) have been designed to use turbofans and these aircraft can operate at service ceilings up to 65,000 ft. At these altitudes the pressure drops to about 6% of ambient conditions and Reynolds numbers throughout the turbine drop precipitously. Understanding and designing for the influence of these large changes in engine Reynolds numbers over the aircraft’s operating range is key to the success of the aircraft and its mission. The present paper documents the influence of chord exit Reynolds number (90,000 to 720,000), inlet turbulence (0.8% and 9%), and exit Mach number (0.7, 0.8, and 0.9) on the exit losses of a first vane design consistent with turbofan engines designed to power high altitude UAVs.

These aerodynamic loss measurements were acquired in a new closed loop compressible flow facility. This closed loop wind tunnel was designed to test turbine cascades over a wide range of Reynolds numbers by controlling the pressure in the tunnel. The current measurements were acquired using a five-hole cone probe controlled with a sealed two-axis traversing system. This first stage vane test section was configured in a three full passage four-vane linear cascade arrangement with upper and lower bleed flows. The low turbulence condition was developed using a flow conditioning section consisting of two perforated plates and two fine-mesh screens and a 4.7 to 1 area ratio nozzle. The high turbulence condition was developed using a simulated combustor. The present results show a significant increase in exit losses with decreasing Reynolds number. This increase in losses is largely due to the thickening of the wake.

Copyright © 2013 by ASME

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