Unsteady Flow Evolution Through a Turning Midturbine Frame Part 2: Spectral Analysis

Lengani, Davide; Spataro, Rosario; Peterleithner, Johannes; Göttlich, Emil

doi:10.2514/1.b35487

Cited by 8 publications

(9 citation statements)

References 35 publications

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“…8) so that the low-energy cores are pushed toward the lower half-channel, and the same effect is induced by the second duct bend. This phenomena affects also the distribution of unsteady pressure fluctuations on the outlet plane, which will be addressed in the companion paper [22].…”

Section: Cfd Resultsmentioning

confidence: 96%

“…1). Plane C is a plane perpendicular to the horizontal direction and is located at 77% of the HP rotor chord downstream of the HP blade trailing edge, whereas plane D (discussed only in part 2 [22]) is inclined by 110 deg to the horizontal direction and, at midspan, its distance from the vane trailing edge (TE) is 14% of the strut axial chord. For plane D, the full area traverses were performed over one strut pitch (22.5 deg), with a measurement grid of 19 positions along the blade span and of 46 positions over one pitch of the strut (Δθ strut ).…”

Section: Measurement Techniquesmentioning

confidence: 99%

“…This first part paper is focused on the analysis of the unsteadiness induced by the HP rotor; the HP shaft encoder only is used for the triple decomposition. The second part of the paper [22] will extend this analysis, reconstructing a phase that takes into account the relative rotor-rotor positions (as introduced in Lengani et al [19]). The FRAPP signal and the two shaft encoders were acquired simultaneously for this further analysis, which will be discussed in detail in the companion paper [22].…”

Section: Data Reductionmentioning

confidence: 99%

“…The validation of the CFD with the experimental data is provided at a selected circumferential position (a more exhaustive validation will be provided in part 2 [22]). Figure 3 shows a time-space plot of the time-resolved total pressure coefficient, which is computed as described in Eq.…”

Section: Unsteady Flow Featuresmentioning

confidence: 99%

“…In this paper, the complex interactions are discussed considering the unsteadiness related to the HP rotor only. The second part of the paper [22] will extend this analysis by means of one-and two-dimensional (2-D) Fourier analysis, which will account for any source of deterministic stresses measured within this facility.…”

mentioning

confidence: 99%

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Unsteady Flow Evolution Through a Turning Midturbine Frame Part 1: Time-Resolved Flow

Lengani

Spataro

Paradiso

et al. 2015

Journal of Propulsion and Power

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This paper identifies and analyzes the propagation of aerodynamic deterministic stresses through a two-spool counter-rotating transonic facility representative of modern and future turbine aeroengine sections. The test setup consists of a high-pressure stage, a diffusing turning midturbine frame with turning struts, and a counter-rotating low-pressure rotor. The flowfield downstream of the high-pressure stage is strongly influenced by the stator-rotor interaction. Such a mechanism interacts again with the downstream turning midturbine frame leading to a vanerotor-vane interaction, which affects the behavior of the low-pressure stage. The results presented were obtained using a fast-response aerodynamic pressure probe for unsteady measurements as well as three-dimensional unsteady Reynolds-averaged Navier-Stokes calculations. The work is presented in two parts. This first part focuses on the explanation of the flow physics that governs the convection of unsteady three-dimensional flow through the midturbine duct. Viscous and inviscid mechanisms are discussed as main drivers for the convection of wakes, secondary vortices, and shocks. The flowfield in the duct is characterized by three superimposed effects: 1) duct diffusion and radial pressure gradient together with turning strut potential field, 2) rotor unsteady work source, and 3) vane/blade interaction phenomena. The understanding of these mechanisms will eventually help to control the unsteadiness content in future architectures where reduced engine component length will enhance the interaction effects.

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Section: Cfd Resultsmentioning

confidence: 96%

Section: Measurement Techniquesmentioning

confidence: 99%

Section: Data Reductionmentioning

confidence: 99%

Section: Unsteady Flow Featuresmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Unsteady Flow Evolution Through a Turning Midturbine Frame Part 1: Time-Resolved Flow

Lengani

Spataro

Paradiso

et al. 2015

Journal of Propulsion and Power

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On Turbulence Measurements and Analyses in a Two-Stage Two-Spool Turbine Rig

Bauinger

Behre

Lengani

et al. 2017

Journal of Turbomachinery

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Since the experiment in turbulence research is of very high importance for evaluating turbulence hypothesis, turbulence measurements were carried out in a two-stage two-spool transonic turbine test rig at the Institute for Thermal Turbomachinery and Machine Dynamics in Graz in which the two rotors are counter-rotating with two different rotational speeds. For the current measurement campaign, triple hot-wire probes, which represent a very new measurement technique in this test rig, were used and their results validated with a fast response aerodynamic pressure probe (FRAPP). Based on the data measured with this device, turbulence intensities may be determined using a method called Fourier filtering. If the classical ensemble averaging procedure with only one trigger is applied, the periodic fluctuations of the other rotor will artificially increase the stochastic fluctuations. Therefore, the two trigger signals of the two rotors require a special analysis method, which was established at Graz University of Technology. The results from this method will be compared to the classical triple decomposition, which uses only one trigger signal. With this analysis tool, it is not only possible to evaluate unsteady signals triggered by one of the two rotors, but also the unsteady interactions of the rotors can be determined and investigated.

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Unsteady Investigation of the Effect of Purge Air on the Flow Field Inside a Turbine Vane Frame Using Particle Image Velocimetry

Schien

Hafizovic

Planck

et al. 2022

Journal of Engineering for Gas Turbines and Power

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Reducing greenhouse gas emissions and high fuel expenses motivates manufacturers to design more efficient aircraft engines. Efficiency can be improved for directly driven jet engines through increased by-pass ratios for high propulsive efficiencies. This measure implies a change in the operating condition of the low-pressure turbine (LPT) towards lower rotational speeds at larger diameters. Turbine vane frames (TVFs) guide the airflow from the high-pressure turbine (HPT) to the LPT in the radial and circumferential direction. The TVF setup integrates turning vanes, and thus removes the need for a vane blade-row in the first LPT stage. Consequently, the TVF benefits the engine weight and length, resulting in efficiency gains. Experimental measurements have been conducted at the two-spool test rig at the Graz University of Technology, consisting of a single-stage HPT, the TVF, and the first LPT rotor. Engine-relevant flow conditions are achieved at the TVF inlet, including HPT tip clearance and purge air effects. Particle Image Velocimetry (PIV) was used to capture the flow field in between two struts of the TVF upstream of the splitter vanes. Flow data in the area of strong interactions between the HPT and the TVF was recorded and discussed in terms of aerodynamic performance. To reveal the unsteady behavior of the fluid, the flow field has been recorded for six serial stator-rotor positions. Two data sets of varying HPT purge flows were obtained to characterize the effect of purge air inside the measurement domain.

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Unsteady Flow Evolution Through a Turning Midturbine Frame Part 2: Spectral Analysis

Cited by 8 publications

References 35 publications

Unsteady Flow Evolution Through a Turning Midturbine Frame Part 1: Time-Resolved Flow

Unsteady Flow Evolution Through a Turning Midturbine Frame Part 1: Time-Resolved Flow

On Turbulence Measurements and Analyses in a Two-Stage Two-Spool Turbine Rig

Unsteady Investigation of the Effect of Purge Air on the Flow Field Inside a Turbine Vane Frame Using Particle Image Velocimetry

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