Acoustic absorption and generation in ducts of smoothly varying area sustaining a mean flow and a mean temperature gradient

Yeddula, Saikumar R.; Gaudron, Renaud; Morgans, Aimee S.

doi:10.1016/j.jsv.2021.116437

Cited by 5 publications

(3 citation statements)

References 39 publications

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“…Because the flow is assumed to be weakly reacting, non-conductive and adiabatic, we neglect the mean-flow heat transfer. For modelling the effect of heat transfer, the reader is referred to Yeddula, Gaudron & Morgans (2021) and Yeddula, Guzmán-Iñigo & Morgans (2022). To close the linear equations, we linearize the Gibbs equation (2.10) and take the material derivative and combine the first-order terms to yield where is the perturbation to the heat-capacity ratio, which is a function of the species mass fractions, , only.…”

Section: Mathematical Modelmentioning

confidence: 99%

Indirect noise from weakly reacting inhomogeneities

2023

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Indirect noise is a significant contributor to aircraft engine noise, which needs to be minimized in the design of aircraft engines. Indirect noise is caused by the acceleration of flow inhomogeneities through a nozzle. High-fidelity simulations showed that some flow inhomogeneities can be chemically reacting when they leave the combustor and enter the nozzle (Giusti et al., Trans. ASME J. Engng Gas Turbines Power, vol. 141, issue 1, 2019). The state-of-the-art models, however, are limited to chemically non-reacting (frozen) flows. In this work, first, we propose a low-order model to predict indirect noise in nozzle flows with reacting inhomogeneities. Second, we identify the physical sources of sound, which generate indirect noise via two physical mechanisms: (i) chemical reaction generates compositional perturbations, thereby adding to compositional noise; and (ii) exothermic reaction generates entropy perturbations. Third, we numerically compute the nozzle transfer functions for different frequency ranges (Helmholtz numbers) and reaction rates (Damköhler numbers) in subsonic flows with hydrogen and methane inhomogeneities. Fourth, we extend the model to supersonic flows. We find that hydrogen inhomogeneities have a larger impact on indirect noise than methane inhomogeneities. Both the Damköhler number and the Helmholtz number markedly influence the phase and magnitude of the transmitted and reflected waves, which affect sound generation and thermoacoustic stability. This work provides a physics-based low-order model which can open new opportunities for predicting noise emissions and instabilities in aeronautical gas turbines with multi-physics flows.

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Section: Mathematical Modelmentioning

confidence: 99%

Indirect noise from weakly reacting inhomogeneities

2023

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“…Yeddula & Morgans [30] derived solutions for the acoustic field in one-dimensional ducts with both arbitrarily varying cross-sectional area and temperature gradient. Further studies investigated the effects of mean flow and mean temperature gradient on acoustic absorption and generation within the duct [31]. Rani & Rani [32] derived two approximate WKB solutions for quasi-onedimensional ducts with arbitrary mean properties and mean flow, while the nonlinear temporal dynamics of acoustic oscillations was discussed by Basu [33].…”

Section: Introductionmentioning

confidence: 99%

Analytical solutions for the acoustic field in thin annular combustion chambers with linear gradients of cross-sectional area and mean temperature

Wang

Nan

Yang

et al. 2023

Aerospace Science and Technology

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“…Much attention has been paid to the distributed properties of unsteady heat sources [20,26,27]. However, even when the heat source is purely steady, steady temperature gradients and mean flow acceleration mean that acoustic waves can be amplified or attenuated by interaction with entropy waves [28][29][30][31][32]. This acoustic-entropy coupling consequently plays a crucial role in determining the frequencies and growth rates of thermoacoustic modes in the presence of temperature gradients [33] and mean flows [34,35].…”

Section: Introductionmentioning

confidence: 99%