The Effects of Vortex Generator Jet Frequency, Duty Cycle, and Phase on Separation Bubble Dynamics The Effects of Vortex Generator Jet Frequency, Duty Cycle, and Phase on Separation Bubble Dynamics
The unsteady environment characterisitic of the low-pressure turbine section in a gas turbine engine effectively reduces the time-averaged separation zone by as much as 35%. Upstream blade rows create unsteady flow disturbances (wakes) that transition the flow. This transitioned flow propagates downstream, re-attaching the separation bubbles on the subsequent blade row. Phase-locked PIV and hot-film measurements were used to document the characteristics of this separation zone when subjected to synchronized unsteady wakes and VGJs. The phase difference between VGJ actuation and the wake passing, blowing ratio, and VGJ duration were optimized to achieve the greatest time-averaged control of the separation zone. The experimental data were used to identify the important characteristics of the wake/jet interaction. Phase-locked PIV measurements were taken to isolate the wake event (wake only), the VGJ event (jets only), and the synchronized combination of unsteady wakes and jets. The synchronized conditions achieved maximum separation bubble control. The presence of wake and jet induced calmed zones are also noted.
School:Brigham Young University
School Location:USA - Utah
Source Type:Master's Thesis
Keywords:vortex generator jets vgj piv pack b turbine blade hot film particle image velocimetry separation wakes
Date of Publication:03/08/2007