Active Boundary Layer Control on a highly loaded Turbine Exit Case profile

Kurz, Julia; Hoeger, Martin; Niehuis, Reinhard

doi:10.29008/etc2017-191

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…This feature allows to change the Reynolds number independently from the Mach number, both at typical levels for turbomachines. Detailed descriptions of the facility can be found in Sturm and Fottner (1985) or Kurz et al (2017).…”

Section: Windtunnel Of the University Of The German Federal Armed Formentioning

confidence: 99%

“…The TEC may be understood as a diffusor, which in upstream direction transforms ambient pressure into lower turbine back-pressure, and by that sets the exit boundary conditions to the LPT. An encouraging approach to shift TEC loading limits towards lower solidity is given by Kurz et al (2017) using pulsed blowing. Highest efficiencies are achieved with optimum boundary conditions and it is clear that the precise understanding of strutted duct flow is important.…”

Section: Introductionmentioning

confidence: 99%

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Impact of vane clocking on the TEC loss in Rig

Hoeger

Baier

Marn

et al. 2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

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The 30% span profile section of the H-TEC highly loaded Turbine Exit Casing was transformed into a plain cascade configuration with identical pressure distribution and loading level. At increasing levels of complexity the incompressible flow in cascade is studied first at different inlet turbulence levels at the Technische Universität Braunschweig. Unsteady inlet conditions were then generated using rotating bars at the cascade wind tunnel of the Armed Forces University Munich at compressible flow speeds and varying Reynolds numbers. Finally the TEC configuration is investigated in the TU Graz STTF 1.5 stage turbine rig using a conventional 5-hole-probe, a miniature Pitot-probe and a hot wire anemometer. A special test-and evaluation concept allows for highly accurate data. The results show a strong vane-TEC clocking, which for the TEC total pressure inlet profile may be approximated by a sine-function. Downstream the TEC, between the wakes, still a sinus shaped total pressure variation is found. Two loss coefficients are evaluated (i) by a classical control volume approach between TEC inlet and exit plane and (ii) by a so-called viscous wake approach. This method compares the viscous flow in the wake region with a hypothetical potential flow deduced from the flow in the same exit plane between the TEC wakes. The viscous wake method compared at 30% span quite nicely to the cascade data. However, the control volume approach yields more than twice the cascade loss, which indicates further loss sources to exist, e.g. unsteady losses to rise from a vane wake-rotor-TEC interaction or turbulence to impact the probe reading. KEYWORDS LPT exit guide vane, TEC, vane clocking, unsteady losses NOMENCLATURE Indices and Abbreviations AR aspect ratio AR=H/c, H passage height Ma 1 inlet Mach number av mass averaged quantity PHI/g normalized circumferential coordinate c, cax chord, axial chord Pit Pitot probe cp 1c pressure coefficient, see eq. (1) Pot quasi potential flow cv control volume loss evaluation Pt, p total pressure, static pressure EIZ+40 wake generator (moving bars) q dynamic head q = Pt-p EIZ_st steady case (without bars) Re 1 Reynolds number g pitch sin all sinus approx. quasi pot. flow all pitch

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Section: Windtunnel Of the University Of The German Federal Armed Formentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of vane clocking on the TEC loss in Rig

Hoeger

Baier

Marn

et al. 2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

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“…To improve the efficiency, the latest investigations at the Institute of Jet Propulsion (ISA) prove for an aerodynamically highly loaded LPT exit casing profile that the mass flow investment of the oscillator can be decreased as low aṡ m osc.,T EC = 2.1 • 10 −4 •ṁ pas.,T EC . The key for this achievement is to consider the AFC in the design process with an optimized position and the right trigger frequency [10][11][12].…”

Section: Abbreviations 1 Introductionmentioning

confidence: 99%

High Frequency Boundary Layer Actuation by Fluidic Oscillators at High Speed Test Conditions

Bettrich

Bitter

Niehuis

2018

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Detailed investigations of high frequency pulsed blowing and the interaction with the boundary layer at high speed test conditions were performed on a flat plate with pressure gradient. This experimental testbed features the imposed suction side flow of an aerodynamically highly loaded low pressure turbine profile. For actuation, a newly developed coupled fluidic oscillator with an independent mass flow and frequency characteristic was tested successfully. Several oscillator operating points were investigated at one turbine profile equivalent operating point with Reynolds number of 70,000, theoretical outflow Mach number of 0.6, and an inflow free stream turbulence level of 4%. The examined frequency range was between 6.5 and 7.5 kHz and the actuation mass flow rates were varied between 0.68% and 1.32% of the overall passage mass flow. As a result, the flow separation and transition can be controlled and the suction side profile losses even halved. Differences in the interaction with the boundary layer of the different oscillator operating points are also presented and discussed.

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Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

Tiainen

Grönman

Jaatinen-Värri

et al. 2017

IJTPP

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Abstract:The decrease in the performance of centrifugal compressors operating at low Reynolds numbers (e.g., unmanned aerial vehicles at high altitudes or small turbomachines) can reach 10% due to increased friction. The purposes of this review are to represent the state-of-the-art of the active and passive flow control methods used to improve performance and/or widen the operating range in numerous engineering applications, and to investigate their applicability in low-Reynolds-number centrifugal compressors. The applicable method should increase performance by reducing drag, increasing blade loading, or reducing tip leakage. Based on the aerodynamic and structural demands, passive methods like riblets, squealers, winglets and grooves could be beneficial; however, the drawbacks of these approaches are that their performance depends on the operating conditions and the effect might be negative at higher Reynolds numbers. The flow control method, which would reduce the boundary layer thickness and reduce wake, could have a beneficial impact on the performance of a low-Reynolds-number compressor in the entire operating range, but none of the methods represented in this review fully fulfil this objective.

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Active Boundary Layer Control on a highly loaded Turbine Exit Case profile

Cited by 3 publications

References 14 publications

Impact of vane clocking on the TEC loss in Rig

Impact of vane clocking on the TEC loss in Rig

High Frequency Boundary Layer Actuation by Fluidic Oscillators at High Speed Test Conditions

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

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