A nonlinear model for indirect combustion noise through a compact nozzle

Huet, Maxime; Giauque, Alexis

doi:10.1017/jfm.2013.442

Cited by 49 publications

(31 citation statements)

References 39 publications

(59 reference statements)

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“…The mechanism by which accelerated entropy waves generate acoustic waves (entropy noise) has been discussed in a number of papers, particularly in the context of nozzles and turbine blade rows (Morfey 1973;Ffowcs Williams & Howe 1975;Marble & Candel 1977;Stow et al 2002;Moase et al 2007;Huet & Giauque 2013).…”

Section: Indirect Noise Generationmentioning

confidence: 99%

Theory and application of reverberated direct and indirect noise

2017

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The generation of a temperature disturbance in a flow is accompanied by the production of acoustic waves (direct noise) and of an entropy perturbation. If this entropy perturbation is accelerated or decelerated (as is the case through a nozzle or flow restriction), additional acoustic waves are generated (indirect noise). Several studies have demonstrated this mechanism in controlled conditions by using entropy wave generators, in which entropy waves are generated and convected through a nozzle, leading to direct and indirect noise. An analytical analysis of the direct and indirect noise produced by the generation and acceleration of entropy waves in a reflective environment is presented. The effect of reverberation (repeated acoustic reflections) on low-frequency perturbations (characteristic of entropy wave generators) is determined analytically. These results are then implemented in a set of limit cases, showing the limit behaviours of such systems. The analytical model is applied to the case of the Cambridge entropy wave generator experiment, in which entropy waves are generated by an electric heater and accelerated through a subsonic orifice plate. Due to the clear time separation of direct and indirect noise in the experimental results, direct and indirect noise transfer functions can be extracted from the experimental data for the first time and compared directly with existing theoretical models. The backward-propagating indirect noise generated at an orifice plate is shown to be significantly higher than predicted by existing theoretical models for isentropic nozzles.

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Section: Indirect Noise Generationmentioning

confidence: 99%

Theory and application of reverberated direct and indirect noise

2017

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“…For more than three decades the formulations of Marble and Candel [12] were the main tools for modeling of acoustic effects of entropy waves in combustion dynamics. Over the last ten years, a number of attempts were made to release the assumptions made by Marble and Candel [12] about the linearity of the system and compactness of the nozzle [13,14,15,16,17,18]. These resulted in improving the predictability of the acoustic conversion of entropy waves.…”

Section: Introductionmentioning

confidence: 99%

On the dissipation and dispersion of entropy waves in heat transferring channel flows

2017

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This paper investigates the hydrodynamic and heat transfer effects upon the dissipation and dispersion of entropy waves in non-reactive flows. These waves, as advected density inhomogeneities downstream of unsteady flames, may decay partially or totally before reaching the exit nozzle, where they are converted into sound. Attenuation of entropy waves dominates the significance of the subsequent acoustic noise generation.Yet, the extent of this decay process is currently a matter of contention and the pertinent mechanisms are still largely unexplored. To resolve this issue, a numerical study is carried out by compressible large eddy simulation (LES) of the wave advection in a channel subject to convective and adiabatic thermal boundary conditions. The dispersion, dissipation and spatial correlation of the wave are evaluated by post-processing of the numerical results. This includes application of the classical coherence function as well as development of nonlinear quantitative measures of wave dissipation and dispersion. The analyses reveal that the high frequency components of the entropy wave are always strongly damped. The survival of the low frequency components heavily depends upon the turbulence intensity and thermal boundary conditions of the channel. In general, high turbulence intensities and particularly heat transfer intensify the decay and destruction of the spatial coherence of entropy waves. In some cases, they can even result in the complete annihilation of the wave. The current work can therefore resolve the controversies arising over the previous studies of entropy waves with different thermal boundary conditions.

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“…When the chamber is terminated by a choked nozzle, the simplest acoustic approximation [125] is to replace it by a wall (Case 6). This low-frequency evaluation can be replaced by more sophisticated approaches when the nozzle cannot be considered as compact compared to the acoustic wavelength [126,127] .…”

Section: The Impedances Of Laboratory Rigsmentioning

confidence: 99%

“…The question of turbomachinery impedances needed to study CIs has many common aspects with the problem of combustion noise [132,133] and especially of noise transmission and generation through turbine stages [126,[134][135][136][137][138][139][140] . This problem has been studied in details over the last 10 years as combustion noise has progressively become a signi cant part of the overall noise of aircraft and helicopters because the other sources of noise (jet noise, fan noise) have decreased.…”

Section: The Impedances Of Compressors and Turbinesmentioning

confidence: 99%

“…The impedance of a nozzle can be computed using compact theories [138,141] (where the wavelength of the acoustic waves is supposed to be large compared to the nozzle axial dimension) or, more recently, new analytical theories [126,127] that provide nozzle impedances at all frequencies corresponding to longitudinal modes. A simple area contraction however is a poor model for what is taking place in a real turbine stage where strong ow deviations are created by vanes.…”

Section: The Impedances Of Compressors and Turbinesmentioning

confidence: 99%

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Prediction and control of combustion instabilities in real engines

Poinsot

2017

Proceedings of the Combustion Institute

517

216

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This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID: 17713Open Archive Toulouse Archive Ouverte (OATAO) OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. To cite this version: AbstractThis paper presents recent progress in the eld of thermoacoustic combustion instabilities in propulsion engines such as rockets or gas turbines. Combustion instabilities have been studied for more than a century in simple laminar con gurations as well as in laboratory-scale turbulent ames. These instabilities are also encountered in real engines but new mechanisms appear in these systems because of obvious differences with academic burners: larger Reynolds numbers, higher pressures and power densities, multiple inlet systems, complex fuels. Other differences are more subtle: real engines often feature speci c unstable modes such as azimuthal instabilities in gas turbines or transverse modes in rocket chambers. Hydrodynamic instability modes can also differ as well as the combustion regimes, which can require very different simulation models. The integration of chambers in real engines implies that compressor and turbine impedances control instabilities directly so that the determination of the impedances of turbomachinery elements becomes a key issue. Gathering experimental data on combustion instabilities is dif cult in real engines and large Eddy simulation (LES) has become a major tool in this eld. Recent examples, however, show that LES is not suf cient and that theory, even in these complex systems, plays a major role to understand both experimental and LES results and to identify mitigation techniques.

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A nonlinear model for indirect combustion noise through a compact nozzle

Cited by 49 publications

References 39 publications

Theory and application of reverberated direct and indirect noise

Theory and application of reverberated direct and indirect noise

On the dissipation and dispersion of entropy waves in heat transferring channel flows

Prediction and control of combustion instabilities in real engines

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