Active Boundary Layer Control with Fluidic Oscillators on Highly-Loaded Turbine Airfoils

Niehuis, Reinhard; Mack, Marion

doi:10.1007/978-3-319-11967-0_1

Cited by 5 publications

(10 citation statements)

References 17 publications

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“…Niehuis and Mack [4] reported that the amplification of Tollmien-Schlichting waves could be beneficial as this would accelerate the transition process. Therefore, a CFD study was conducted with MISES to determine the boundary layer data at the location of the fluidic actuators.…”

Section: Actuation Frequencymentioning

confidence: 99%

“…For the investigations, active flow control by fluidic oscillators was chosen as flow control method. Cattafesta and Sheplak [3] and Niehuis and Mack [4] compared in their articles many different methods for boundary layer control. As the profile was expected to suffer from negative flow separation effects only in the low Reynolds number regime, passive methods were excluded.…”

Section: Introductionmentioning

confidence: 99%

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Active Boundary Layer Control on a Highly Loaded Turbine Exit Case Profile

Kurz

Hoeger

Niehuis

2018

IJTPP

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A highly loaded turbine exit guide vane with active boundary layer control was investigated experimentally in the High Speed Cascade Wind Tunnel at the University of the German Federal Armed Forces, Munich. The experiments include profile Mach number distributions, wake traverse measurements as well as boundary layer investigations with a flattened Pitot probe. Active boundary layer control by fluidic oscillators was applied to achieve improved performance in the low Reynolds number regime. Low solidity, which can be applied to reduce the number of blades, increases the risk of flow separation resulting in increased total pressure losses. Active boundary layer control is supposed to overcome these negative effects. The experiments show that active boundary layer control by fluidic oscillators is an appropriate way to suppress massive open separation bubbles in the low Reynolds number regime.

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Section: Actuation Frequencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Active Boundary Layer Control on a Highly Loaded Turbine Exit Case Profile

Kurz

Hoeger

Niehuis

2018

IJTPP

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“…closed-loop designs like in the work of King et al [1]. Other applications are considered to be active if the actuator is switched on and off when needed, as outlined in the review paper by Niehuis and Mack [2]. In some cases, feedback control cannot be applied due to small geometries, high temperatures or frequencies, or if it is just the more expedient approach.…”

Section: Abbreviations 1 Introductionmentioning

confidence: 99%

“…Modern LPTs are aerodynamically highly loaded, usually featuring flow separation on the suction side towards low Reynolds number operating points. Since the high speed investigations at ISA showed many promising results [2,9,13,14] for AFC applied on the T161, this paper focuses on a T161-like suction side flow of a flat plate with pressure gradient. The massive flow separation is controlled with high frequency periodic excitation [15], induced by a newly developed coupled fluidic oscillator [16].…”

Section: Abbreviations 1 Introductionmentioning

confidence: 99%

“…The TS waves or instabilities develop naturally in the laminar boundary layer and can therefore triggered [17]. The instabilities developing and growing within the shear layer for separated flows are commonly known as KH instabilities [18]. Consequently, the goal is to trigger with the most effective frequency in the range of the boundary layer receptivity to amplify linear instability effects and therefore use this interaction within the boundary layer for a controlled transition towards a turbulent boundary layer.…”

Section: Abbreviations 1 Introductionmentioning

confidence: 99%

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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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Application of slotted blade in the improvement of turbomachinery performance

et al. 2021

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Flow separation is ubiquitous in turbomachinery. Compared with the more mature turbomachinery flow separation control method where the medium is gas, the turbomachinery flow separation method where the medium is liquid cannot be controlled well. In this study, according to the flow separation control principle of the aircraft fowler flap, taking the stator blade of the hydraulic torque converter as the basic research object, the stator blade shape is fitted with Joukowsky transformation, and then it is slotted. Computational fluid dynamics is used to perform flow analysis on original blades and slotted blades. It is found that compared with that of the original blade, the slotted blade’s flow separation phenomenon is effectively suppressed, turbulent kinetic energy is reduced, flow is more stable, and energy loss is reduced. In addition, using slotted blades for torque converter simulation, the torque ratio is increased by up to 0.245, and the efficiency is increased by up to 5%, which shows that slotted blades can improve the mechanical performance of the pump wheel and are not limited to the torque converter.

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Active Boundary Layer Control with Fluidic Oscillators on Highly-Loaded Turbine Airfoils

Cited by 5 publications

References 17 publications

Active Boundary Layer Control on a Highly Loaded Turbine Exit Case Profile

Active Boundary Layer Control on a Highly Loaded Turbine Exit Case Profile

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

Application of slotted blade in the improvement of turbomachinery performance

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