Sound emission of a turbine stage due to an azimuthally periodic mean temperature

Mu, Zhongqiang; Michel, U.; Steger, Mathias; Ashcroft, Graham; Kennepohl, Fritz; Thiele, Frank

doi:10.1177/1475472x15627408

Cited by 2 publications

(5 citation statements)

References 24 publications

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“…Different strategies have been employed to estimate the indirect noise generation as disturbances propagate through the turbine ranging from analytical modelling [5] to three-dimensional compressible flow simulations [6,9]. Analytical approaches focused initially on the one-dimensional transmission properties of compact nozzles [5,10] and were extended to non-compact nozzles [11] with two-dimensional domains [12] including shock waves [13].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, three-dimensional compressible flow simulations have been used to investigate the impact of non-uniform temperature distributions on the propagation in turbine blade rows. Mu et al [9] reported a significant turbine noise amplification with a non-uniform mean temperature pattern mimicking individual burners. Transient entropy waves being entrained into turbines are elongated by the acceleration forming streaks.…”

Section: Introductionmentioning

confidence: 99%

“…All investigations employed idealised entropy wave shapes, i.e. spots [15,17] or plane waves [9]. Further, investigation treated vorticity and entropy waves separately.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors

Semlitsch¹,

Hynes²,

Langella

et al. 2019

Journal of Propulsion and Power

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Understanding the nature of the unsteady flow at the combustor exit is required to accurately simulate time dependent phenomena in the turbine entry, such as indirect noise generation. Using Large Eddy Simulations of the combustion process in a realistic geometry, we analyse the flow at its exit. Two realistic, near-ground certification operating conditions are considered. Different mechanisms for large-scale flow and thermal structure generation are described, which are ejected into the turbine. Modal decomposition methods are used to extract the spatial and temporal scales at the turbine entry. We find that, depending on the operating condition, the entropy waves convect as elongated streaks in the core of the combustor annulus or the proximity of the walls. The dominant unsteady character of the fluctuations exhibits different spectral properties, i.e. low-frequency in the core and high-frequency towards walls. At the combustor exit, the vortical field is dominated by the swirl in the air inlet, which is found to have little influence on the entropy perturbations. Further, the importance of considering the interaction of multiple fuel injectors and combustion zones in an annular combustor is investigated. It is shown that pulsating circumferential vorticity modes can occur in multi-sector annular combustors but these, however, do not affect the entropy wave distribution.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors

Semlitsch¹,

Hynes²,

Langella

et al. 2019

Journal of Propulsion and Power

View full text Add to dashboard Cite

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“…The excitation of additional modes due to streak-rotor interaction is also reported by Mu et al [9]. Note that the configuration without streak was simulated using the same mesh with two stator passages and the same 2D inflow boundary condition but with ∆T = 0 K. This allows the evaluation of a signal-to-noise ratio for the additional acoustic modes due to the presence of the streaks.…”

Section: Impact Of Hot Streaks On the Resultsmentioning

confidence: 74%

“…In the relative frame of reference of a turbine rotor, they produce unsteady temperature variations which can potentially produce blade passing frequency tones when convected through the turbine following the mechanism described previously. Mu et al [8,9] investigated the interaction of non-uniform mean flow temperature with the second stage of a high-pressure turbine. The turbine interaction with a low count of steady hot streaks was found to have a strong impact on acoustics.…”

Section: Introductionmentioning

confidence: 99%

CFD-Based Investigation of Turbine Tonal Noise Induced by Steady Hot Streaks †

Holewa

Lesnik

Ashcroft

et al. 2017

IJTPP

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Abstract:The interaction of steady hot streaks from an annular ring of combustion chambers with turbine rotating blades can potentially generate tonal noise. The relevance of this source mechanism in aeroengine noise is controversially discussed in the literature. In the present paper, the streak-turbine interaction is investigated using the computational fluid dynamics (CFD) method called harmonic balance (HB)-a truncated non-linear frequency domain approach with a high potential of reducing the computational effort. The investigated high-pressure turbine is composed of a single stator-rotor stage. The first part of the present paper compares the results obtained with the HB method to those obtained with the more established time-accurate unsteady Reynolds-averaged Navier-Stokes (URANS) approach and investigates their sensitivity with respect to the computational mesh density. Thereby, no streaks are simulated, and only the turbine alone tones are considered. Convincing results are obtained on aerodynamics and acoustics. The second part of the paper deals with a parametric study on the acoustical impact of steady hot streaks. The streaks are prescribed at the inlet of the stage using a boundary condition as an attempt to simulate a ring of combustor nozzles. No vorticity is coupled into the computational domain, as the objective is to measure the effect of temperature inhomogeneity only. Overall, the turbine appears to be slightly quieter with hot streaks. The streak-to-stator-vane ratio of 1-to-2 explains the generation of new acoustic modes with distinct azimuthal orders. The acoustic power amplitude of those additional modes scales roughly with the square of the temperature difference, the fourth-power of the diameter, and the square of the entropy difference. This last result agrees well with the 1D theory of Marble and Candel. The acoustic contribution of the unsteady force on the rotor blades due to the overspeed measured in the wakes of the streaks-resulting from the flow acceleration through the stator-remains an open question.

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Sound emission of a turbine stage due to an azimuthally periodic mean temperature

Cited by 2 publications

References 24 publications

Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors

Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors

CFD-Based Investigation of Turbine Tonal Noise Induced by Steady Hot Streaks †

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