Steady and Unsteady CFD Calculation of the Laminar-to-Turbulent Transition in a Turning Mid Turbine Frame With Embedded Design

Bader, Pascal; Sanz, Wolfgang

doi:10.1115/gt2015-42617

Cited by 4 publications

(3 citation statements)

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“…Whereas the highest loss occurs in the strut wake in the baseline design, the losses are more evenly distributed in the embedded design. In a succeeding study of the unsteady flow, Spataro et al [12] and Bader et al [14] proved experimentally and numerically a positive effect. Both publications showed a damping of the unsteady fluctuation by the splitters.…”

Section: Discussionmentioning

confidence: 99%

“…Spataro et al already showed in steady [11] and unsteady [12] measurements the reduction of the nonuniformity of pressure fluctuations (reduced strut wakes and secondary vortices) of the embedded design. In addition to the measurements, steady [13] and unsteady [14] computational fluid dynamics (CFD) simulations have been performed at the Institute for Thermal Turbomachinery and Machine Dynamics to analyze the flow structures within the TMTF with the embedded design.…”

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confidence: 99%

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Flow Evolution Through a Turning Midturbine Frame with Embedded Design

Bader¹,

Sanz²,

Spataro

et al. 2017

Journal of Propulsion and Power

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The paper discusses the time-averaged flow of a new-concept turbine transition duct placed in a two-stage counter-rotating test turbine. As a possible architecture for the turbine transition duct of future engines, the structural vanes carrying the bearing loadings can be integrated with the first low-pressure vane row in one aerodynamically optimized wide-chord vane called the turning midturbine frame. To increase the flow uniformity and to decrease the unsteady content of the flow, a baseline turning midturbine frame is redesigned by embedding two splitter vanes into the strut passage. The discussion on the flowfield is based on numerical results obtained by computational fluid dynamics and validated by aerodynamic measurements. In particular, the splitters are seen playing a major role in suppressing the big structures generated by the struts and the secondary flows of the high-pressure turbine. On the other hand, new losses are introduced by the splitters. Such structures play a decisive role in the overall component performance; therefore, their effect should be properly understood. This work provides a deep insight into the flow physics of an embedded turning midturbine frame for next-generation aeroengines, which is seen as a promising architecture in order to compact the engine size while keeping component performance high. The present work can be considered as a first attempt to implement splitter blades into an already existing turning midturbine frame design, and its value lies in a thorough experimental and computational study on the losses and benefits of such a design.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Flow Evolution Through a Turning Midturbine Frame with Embedded Design

Bader¹,

Sanz²,

Spataro

et al. 2017

Journal of Propulsion and Power

Self Cite

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“…The state of this boundary layer, whether it is laminar or turbulent, is on one hand influenced by free stream parameters, like the velocity, acceleration or turbulence level of the free stream and on the other hand influences the free stream itself as well as wall parameters, like skin friction or heat transfer (see e.g. Bader and Sanz [2015]).…”

Section: Introductionmentioning

confidence: 99%

Measurement and simulation of a turbulent boundary layer exposed to acceleration along a flat plate

Bader

Sanz

2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

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Flow in turbomachines is generally highly turbulent. The boundary layers, however, often exhibit laminar-to-turbulent transition. But also relaminarization of the turbulent flow may occur. It is therefore important for the designer to understand the process of boundary layer transition in both directions and to determine the position of transition onset and the length of the transitional region. In the last decades several transition models have been developed to enable modern CFD codes to predict the transition and relaminarization processes. This has the advantage that the boundary layer behavior can be analyzed in advance, which enables the design of blades which trigger a "suitable" boundary layer. But in order to use CFD for designing tasks, the code must predict accurately and reliably the transition and relaminarization processes within the boundary layer. Therefore in this work, the γ-Re θ transition model is tested regarding relaminarization prediction. An in-house flat plate test case is analyzed where extensive measurement results are available. Since the test case shows flow pulsations caused by a separation bubble, different cases are investigated where either the full range of the measured velocity fluctuations or only the fluctuations above the integral subscale are prescribed as boundary conditions. Both boundary conditions are combined with either a steady or unsteady simulation where the latter allows to consider the velocity fluctuations additionally. Aim of this variation is to understand the influence of inlet turbulence boundary condition of the predictions of the transition model regarding relaminarization.

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Experimental Investigation of Boundary Layer Relaminarization in Accelerated Flow

Bader

Pschernig

Sanz

et al. 2018

Journal of Fluids Engineering

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Flow in turbomachines is generally highly turbulent. Nonetheless, boundary layers may exhibit laminar-to-turbulent transition, and relaminarization of the turbulent flow may also occur. The state of flow of the boundary layer is important since it influences transport phenomena like skin friction and heat transfer. In this paper, relaminarization in accelerated flat-plate boundary-layer flows is experimentally investigated, measuring flow velocities with laser Doppler anemometry (LDA). Besides the mean values, statistical properties of the velocity fluctuations are discussed in order to understand the processes in relaminarization. It is shown that strong acceleration leads to a suppression of turbulence production. The velocity fluctuations in the accelerated boundary layer flow “freeze,” while the mean velocity increases, thus reducing the turbulence intensity. This leads to a laminar-like velocity profile close to the wall, resulting in a decrease of the local skin friction coefficient. Downstream from the section with enforced relaminarization, a rapid retransition to turbulent flow is observed. The findings of this work also describe the mechanism of retransition.

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Steady and Unsteady CFD Calculation of the Laminar-to-Turbulent Transition in a Turning Mid Turbine Frame With Embedded Design

Cited by 4 publications

References 0 publications

Flow Evolution Through a Turning Midturbine Frame with Embedded Design

Flow Evolution Through a Turning Midturbine Frame with Embedded Design

Measurement and simulation of a turbulent boundary layer exposed to acceleration along a flat plate

Experimental Investigation of Boundary Layer Relaminarization in Accelerated Flow

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