A Comparison of Combustor-Noise Models

Hultgren, Lennart S.

doi:10.2514/6.2012-2087

Cited by 10 publications

(4 citation statements)

References 34 publications

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“…Core noise is projected to become an important component of the noise of next generation aircraft (see Ref. [1]). This is because other dominant noise components such as jet noise and fan noise have been substantially reduced in recent years by the introduction of high bypass ratio engines with innovative fan blade design and the use of effective acoustic liners and other noise suppressors.…”

Section: Introductionmentioning

confidence: 99%

The Spectral Shape of Combustion Noise

Tam

2015

International Journal of Aeroacoustics

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In this paper, it is proposed that the spectral shape of combustion noise is the same as the similarity spectrum of the noise from the large turbulence structures of high-speed jets. This is true regardless of the turbulence level in the combustion process, the equivalence ratio of the fuel or whether the fuel is a gas or a liquid as long as it is hydrocarbon. At the present time, the mechanism by which combustion noise is generated is still not known. So, it is not possible to prove the correctness of the proposal theoretically or computationally. Here, an empirical approach is followed. Comparisons between the similarity spectrum and many sets of combustion noise spectra are made. The spectra are from open flames, low speed jets, can-type combustor, auxiliary power units and turbofan engines noise measurements. Good agreements are found offering favorable support for the proposal. This paper is written in honor of Dr. Marvin E. Goldstein, a world-class aeroacoustician, an accomplished applied mathematician and a much-respected long time friend.

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Section: Introductionmentioning

confidence: 99%

The Spectral Shape of Combustion Noise

Tam

2015

International Journal of Aeroacoustics

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“…Currently, prediction methods for core noise at the system level are entirely empirical [56] or based on the work of Chu [37]. Use of Equation ( 37) with all source terms combined with a modern LES of the core itself and a tailored vector Green's function of the engine geometry and mean flow will produce a prediction without all the assumptions inherent in the NASA Aircraft Noise Prediction Program (ANOPP/2) [57]. Also, a simplified form that will use little modification relative to standard acoustic prediction models appears in Equation (39).…”

Section: Applicationsmentioning

confidence: 99%

Analytical Equations for Thermoacoustic Instability Sources and Acoustic Radiation from Reacting Turbulence

Miller

2020

International Journal of Aerospace Engineering

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We seek to ascertain and understand source terms that drive thermoacoustic instability and acoustic radiation. We present a new theory based on the decomposition of the Navier-Stokes equations coupled with the mass fraction equations. A series of solutions are presented via the method of the vector Green’s function. We identify both combustion-combustion and combustion-aerodynamic interaction source terms. Both classical combustion noise theory and classical Rayleigh criterion are recovered from the presently developed more general theory. An analytical spectral prediction method is presented, and the two-point source terms are consistent with Lord Rayleigh’s instability model. Particular correlations correspond to the source terms of Lighthill, which represent the noise from turbulence and additional terms for the noise from reacting flow.

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“…Core noise is projected to be an important component of propulsive noise of the next generation aircraft (see Ref. [1]). This is because traditionally dominant noise components such as jet noise and fan noise have been substantially reduced in recent years by the introduction of high bypass ratio engines, by the use of geared fans and by incorporating innovative fan blade designs including sweep and lean technology and the use of advanced acoustics liners and other noise suppressors.…”

Section: Introductionmentioning

confidence: 99%

Combustion noise: modeling and prediction

et al. 2019

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This paper reviews both direct and indirect combustion noise. For convenience, they will simply be referred to as combustion noise and entropy noise. Combustion noise has been studied for well over half a century. However, because of the large number of parameters involved and the complexities inherent in the combustion processes, a widely accepted theory has yet to be developed. For this reason, this review focuses primarily on experimental measurements, semi-empirical relations and empirical but practical prediction methodologies. Important characteristic features and empirical correlations of combustion noise based on open flames and engine noise data are highlighted. Plausible generation of entropy noise by the passage of entropy waves through a nonuniform mean flow was first predicted theoretically circa 1970s. But it took forty years for its existence to be confirmed experimentally. Since then, there have been numerous publications on this subject. They are the primary materials of this review. The fundamental experiment and noise generation mechanism will be discussed first. Of great practical importance is whether there is significant generation of entropy waves inside an engine. This issue and new methods for modeling and predicting internally generated engine entropy noise are items that are examined at some length. Recent advances in computational methods especially in large eddy simulation lead us to envision an important role to be played by high-fidelity numerical simulation in future combustion and entropy noise research and prediction. A critical evaluation of a strategy for investigating and predicting the generation and propagation of these noise components from the combustor of an engine to its exhaust is included in this review.

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A Comparison of Combustor-Noise Models

Cited by 10 publications

References 34 publications

The Spectral Shape of Combustion Noise

The Spectral Shape of Combustion Noise

Analytical Equations for Thermoacoustic Instability Sources and Acoustic Radiation from Reacting Turbulence

Combustion noise: modeling and prediction

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