Influence of Vortex Generator Jet-Induced Transition on Separating Low Pressure Turbine Boundary Layers

Reimann, Daniel; Bloxham, Matthew; Crapo, K.; Pluim, Jonathan; Bons, Jeffrey P.

doi:10.2514/6.2006-2852

Cited by 12 publications

(3 citation statements)

References 9 publications

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“…Pulsed VGJs were found to be considerably more effective than steady VGJs. The complementary roles of transition and streamwise vorticity in aiding the separation control phenomenon have also been explored in detail (Reimann et al, 2006. The wake loss coeffi cient could be reduced by more than 50% using pulsed VGJs (Bons et al, 2001a).…”

Section: A Overviewmentioning

confidence: 99%

“…To better understand the role of boundary-layer transition in the unsteady fl ow control process, Reimann et al (2006) acquired phase-averaged velocity and turbulence data in the LPT separated shear layer with and without pulsing. The data included a quantitative measure of intermittency to determine the state of the boundary layer (i.e., laminar, transitional, or fully turbulent).…”

Section: Fig 11 Integrated Wake Loss Coeffi Cient (G Int ) Normalizementioning

confidence: 99%

“…The wall pressure coeffi cient as computed from the temporal and spanwise average of the simulation data and the attached fl ow pressure distribution obtained from a design code (MISES) (Reimann et al, 2006) are shown in Fig. 45a.…”

Section: Open-loop Control (3-d)mentioning

confidence: 99%

See 2 more Smart Citations

Fundamentals and Applications of Modern Flow Control

Joslin¹,

Miller²,

Miller³

2009

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Section: A Overviewmentioning

confidence: 99%

Section: Fig 11 Integrated Wake Loss Coeffi Cient (G Int ) Normalizementioning

confidence: 99%

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Fundamentals and Applications of Modern Flow Control

Joslin¹,

Miller²,

Miller³

2009

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Synchronizing Separation Flow Control With Unsteady Wakes in a Low-Pressure Turbine Cascade

Bloxham

Reimann

Crapo

et al. 2009

Journal of Turbomachinery

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Particle image velocimetry (PIV) measurements were made on a highly loaded low-pressure turbine blade in a linear cascade. The Pack B blade has a design Zweifel coefficient of 1.15 and a peak Cp at 63% axial chord on the suction surface. Data were taken at Rec=20K with 3% inlet freestream turbulence and a wake-passing flow coefficient of 0.8. Without unsteady wakes, a nonreattaching separation bubble exists on the suction surface of the blade beginning at 68% axial chord. The time-averaged separation zone is reduced in size by approximately 35% in the presence of unsteady wakes. Phase-locked hot-wire and PIV measurements were used to document the dynamics of this separation zone when subjected to synchronized, unsteady forcing from a spanwise row of vortex generator jets (VGJs) in addition to the unsteady wakes. The phase difference between VGJ actuation and the wake passing was optimized. Both steady state Cp and phase-locked velocity measurements confirm that the optimal combination of wakes and jets yields the smallest separation.

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The Application of Flow Control to an Aft-Loaded Low Pressure Turbine Cascade With Unsteady Wakes

Bons

Pluim

Gompertz

et al. 2011

Journal of Turbomachinery

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The synchronous application of flow control in the presence of unsteady wakes was studied on a highly loaded low pressure turbine blade. At low Reynolds numbers, the blade exhibits a nonreattaching separation bubble under steady flow conditions without upstream wakes. Unsteady wakes from an upstream vane row are simulated with a moving row of bars. The separation zone is modified substantially by the presence of unsteady wakes, producing a smaller separation zone and reducing the area-averaged wake total pressure loss by more than 50%. The wake disturbance accelerates transition in the separated shear layer but stops short of reattaching the flow. Rather, a new time-averaged equilibrium location is established for the separated shear layer. The focus of this study was the application of pulsed flow control using two spanwise rows of discrete vortex generator jets. The jets were located at 59% Cx, approximately the peak cp location, and at 72% Cx. The most effective separation control was achieved at the upstream location. The wake total pressure loss decreased 60% from the wake-only level and the cp distribution fully recovered its high Reynolds number shape. The jet disturbance dominates the dynamics of the separated shear layer, with the wake disturbance assuming a secondary role only. When the pulsed jet actuation was initiated at the downstream location, synchronizing the jet to actuate between wake events was key to producing the most effective separation control. Evidence suggests that flow control using vortex generator jets (VGJs) will be effective in the highly unsteady low pressure turbine environment of an operating gas turbine, provided the VGJ location and amplitude are adapted for the specific blade profile.

show abstract

Influence of Vortex Generator Jet-Induced Transition on Separating Low Pressure Turbine Boundary Layers

Cited by 12 publications

References 9 publications

Fundamentals and Applications of Modern Flow Control

Fundamentals and Applications of Modern Flow Control

Synchronizing Separation Flow Control With Unsteady Wakes in a Low-Pressure Turbine Cascade

The Application of Flow Control to an Aft-Loaded Low Pressure Turbine Cascade With Unsteady Wakes

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