Time-Dependent Pressure Fluctuations on an Oscillating Turbine Cascade at Transonic Off-Design Flow Conditions

Bölcs, A.; Fransson, Torsten; Körbächer, H.

doi:10.1007/978-1-4613-9341-2_27

Cited by 8 publications

(3 citation statements)

References 4 publications

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“…The cascade considered for the study consisted of a NACA 65 series airfoil, Standard Test Configuration 1 (Bölcs et al [8]), with a camber angle of 10° and chord 152 mm. The cascade consists of five airfoils with a spacing of 60.5 mm.…”

Section: Methodsmentioning

confidence: 99%

Effect of Adjacent Blade Oscillation on the Forces on A Blade of a Compressor Cascade

Keerthi,

Kushari

2023

joast

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The current trend of aircraft engines is one towards attaining high isentropic efficiency while minimizing its weight. This leads to a state where the blades are highly loaded and consequently susceptible to vibrations. High cycle fatigue caused as a result of such self-excited flutter or forced vibration due to defects in the air stream are detrimental to the engine. An understanding of the onset of instabilities is essential to predict their occurrences to avoid a catastrophic failure during operation or costly redesign during the development phase. The critical parameters in turbomachine aeroelasticity are the reduced frequency and the interblade phase angle. The damping of the system is known to be a function of the phase difference between the blade forces and the blade motion. In the present study, a linear cascade of five blades is considered to understand the effect of harmonically varying boundary conditions. The second and fourth blades of the cascade are subjected to torsional oscillation by an external mechanism. The third blade, considered as the reference, is stationary and instrumented. The unsteady pressure along the reference blade surface is measured simultaneously with the loads acting on the blade. The unsteady pressures are measured using a multi-sensor pressure scanner by multiplexing and the loads are measured using a five-channel strain gage balance. The blade displacement is determined from the integrated accelerometer signal mounted on an oscillating blade. The experiments are conducted at a low-subsonic speed and multiple oscillation frequencies. The cascade is set at zero incidence and four stagger angles. The effect of inter-blade phase angle is included as the oscillation of the walls adjacent to the reference blade. The phase difference between the harmonic motion of the neighboring walls and the pressure and load signals on the reference blade is related to the damping characteristics of the reference blade. The variation in damping is studied for the range of blade motion phase difference angles and reduced frequencies. The effect of the phase difference between the oscillating blades is seen to strongly affect the damping characteristics of the reference airfoil.

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Section: Methodsmentioning

confidence: 99%

Effect of Adjacent Blade Oscillation on the Forces on A Blade of a Compressor Cascade

Keerthi,

Kushari

2023

joast

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“…Experiments were done to obtain steady state and time dependent informations about pressure responses at high incidence flow angles with separated flow regions and near oscillating shock waves. The problem of periodicity and repetitivity of steady-state and unsteady measurements at high incidence angles was already mentioned by BOIcs, Fransson and KOrbacher (1991). Tests that were performed to check the periodicity and repetitivity of the measurement are presented in this paper in more detail.…”

Section: Introductionmentioning

confidence: 89%

Periodicity and Repetivity of Unsteady Measurements of an Annular Turbine Cascade at Off Design Flow Conditions

Bölcs

Körbächer

1993

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery

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A two-dimensional section of a gas turbine cascade has been investigated experimentally in an annular non-rotating cascade facility as regards to its steady-state and time-dependent aerodynamic characteristics at off-design flow conditions. The blades vibrated in the first traveling wave bending mode. Steady-state and unsteady data were obtained for an off-design incidence angle of about 22° and for an isentropic outlet Mach number of M2s=1.19. At this flow condition, a separation bubble was present on the suction surface close to the leading edge. A shock appeared at trans- and supersonic outlet flow conditions on the suction surface. The data showed high unsteady loads close to the leading edge and in the shock region. It was found that the steady and the unsteady pressures in the shock region on the blade surface seemed to be very sensitive to small changes in the flow conditions. The periodicity and repetitivity of the steady and the unsteady pressures (σ=180°) was checked at several circumferential channel positions. This was done to figure out to which extend test data obtained in an annular ring channel can serve as a basis for the comparison with numerically obtained data. The aim of this paper is to show where problems may arise when comparing calculated results with test data.

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“…Flutter experiments have been conducted traditionally in sector or annular cascades in academic laboratories prescribing the harmonic motion of a single (Vogt and Fransson, 2006) or a set of airfoils (Bölcs and Fransson, 1986). The unsteady pressures on the airfoil and the aerodynamic work are the output of these experiments.…”

Section: Introductionmentioning

confidence: 99%

Mach number influence on low-pressure turbine flutter

Escudero,

Corral,

Blando

2024

J. Glob. Power Propuls. Soc.

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The effect of the Mach number on the vibration amplitude trends of an isolated low-pressure turbine rotor is described. The study utilizes an analytical model correlating the aerodynamic work and the dry-friction work. Aerodynamic damping has been obtained using a frequency domain linearized Navier-Stokes solver, whereas friction damping has been modeled using a heuristic micro-slip model calibrated with the experimental data. In order to validate the analytical predictions, an extensive experimental campaign was conducted. Unsteady pressure transducers flushed mounted in the outer casing, one chord downstream of the trailing edge of the rotor, were used to characterize the vibration of the rotor. The analysis reveals a significant influence of the Mach number on the work balance between aerodynamic and mechanical components. It is observed that the vibration amplitude and the flutter-induced unsteady pressure perturbations of low-pressure turbine rotor blades notably increases when the exit Mach number does.

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Time-Dependent Pressure Fluctuations on an Oscillating Turbine Cascade at Transonic Off-Design Flow Conditions

Cited by 8 publications

References 4 publications

Effect of Adjacent Blade Oscillation on the Forces on A Blade of a Compressor Cascade

Effect of Adjacent Blade Oscillation on the Forces on A Blade of a Compressor Cascade

Periodicity and Repetivity of Unsteady Measurements of an Annular Turbine Cascade at Off Design Flow Conditions

Mach number influence on low-pressure turbine flutter

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