Some results in combustion generated noise

Strahle, Warren C.

doi:10.2514/6.1972-198

Cited by 16 publications

(27 citation statements)

References 2 publications

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“…Strahle used equation 2.8 as a basis for providing estimations of the total acoustic power as a function of the flow/flame parameters such as U, S L and l T ( [Strahle, 1971[Strahle, , 1972[Strahle, , 1978[Strahle, , 1985).…”

Section: Literature Reviewmentioning

confidence: 99%

Sound generation by turbulent premixed flames

et al. 2018

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This paper presents a numerical study of the sound generated by turbulent, premixed flames. Direct numerical simulations (DNS) of two round jet flames with equivalence ratios of 0.7 and 1.0 are first carried out. Single-step chemistry is employed to reduce the computational cost, and care is taken to resolve both the near and far fields and to avoid noise reflections at the outflow boundaries. Several significant features of these two flames are noted. These include the monopolar nature of the sound from both flames, the stoichiometric flame being significantly louder than the lean flame, the observed frequency of peak acoustic spectral amplitude being consistent with prior experimental studies and the importance of so-called ‘flame annihilation’ events as acoustic sources. A simple model that relates these observed annihilation events to the far-field sound is then proposed, demonstrating a surprisingly high degree of correlation with the far-field sound from the DNS. This model is consistent with earlier works that view a premixed turbulent flame as a distribution of acoustic sources, and provides a physical explanation for the well-known monopolar content of the sound radiated by premixed turbulent flames.

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Section: Literature Reviewmentioning

confidence: 99%

Sound generation by turbulent premixed flames

et al. 2018

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“…Lean premixed combustors, designed to reduce nitric oxide emissions significantly, are especially prone to these oscillations which can lead to vibrations and structural damage (Krebs et al 2002;Schuermans, Bellucci & Paschereit 2003;Lieuwen & Yang 2005). These unsteady phenomena come from the interaction between acoustics and heat-release fluctuations which act as a volume acoustic source (Strahle 1972). In annular combustion chambers (figure 2), these instabilities often take the form of azimuthal modes (Krebs et al 2002;Schuermans et al 2003;Parmentier et al 2012;Worth & Dawson 2013a,b;Bauerheim et al 2014c).…”

Section: Introductionmentioning

confidence: 99%

Symmetry breaking of azimuthal thermo-acoustic modes in annular cavities: a theoretical study

et al. 2014

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Many physical problems containing rotating symmetry exhibit azimuthal waves, from electromagnetic waves in nanophotonic crystals to seismic waves in giant stars. When this symmetry is broken, clockwise (CW) and counter-clockwise (CCW) waves are split into two distinct modes which can become unstable. This paper focuses on a theoretical study of symmetry breaking in annular cavities containing a number $N$ of flames prone to azimuthal thermo-acoustic instabilities. A general dispersion relation for non-perfectly-axisymmetric cavities is obtained and analytically solved to provide an explicit expression for the frequencies and growth rates of all azimuthal modes of the configuration. This analytical study unveils two parameters affecting the stability of the mode: (i) a coupling strength corresponding to the cumulative effects of the $N$ flames and (ii) a splitting strength due to the symmetry breaking when the flames are different. This theory has been validated using a 3D Helmholtz solver and good agreement is found. When only two types of flames are introduced into the annular cavity, the splitting strength is found to depend on two parameters: the difference between the two burner types and the pattern used to distribute the flames along the azimuthal direction. To first order, this theory suggests that the most stable configuration is obtained for a perfectly axisymmetric configuration. Therefore, breaking the symmetry by mixing different flames cannot improve the stability of an annular combustor independently of the flame distribution pattern.

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“…The volume sources describe fluctuations of the reaction progress variable and are not necessarily accompanied by the generation of entropy fluctuations. The volume source term and fluctuating heat of combustion are related to each other by assuming an incompressible low-Mach number flame, leading to the following relation [26]…”

Section: Governing Equations 21 Linearized Navier-stokes Equations (mentioning

confidence: 99%

Prediction of Combustion Noise in a Model Combustor Using a Network Model and a LNSE Approach

Ullrich

Mahmoudi

Lackhove

et al. 2017

Journal of Engineering for Gas Turbines and Power

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The reduction of pollution and noise emissions of modern aero engines represents a key concept to meet the requirements of the future air traffic. This requires an improvement in the understanding of combustion noise and its sources, as well as the development of accurate predictive tools. This is the major goal of the current study where the low-order thermo-acoustic network (LOTAN) solver and a hybrid computational fluid dynamics/computational aeroacoustics approach are applied on a generic premixed and pressurized combustor to evaluate their capabilities for combustion noise predictions. LOTAN solves the linearized Euler equations (LEE) whereas the hybrid approach consists of Reynolds-averaged Navier–Stokes (RANS) mean flow and frequency-domain simulations based on linearized Navier–Stokes equations (LNSE). Both solvers are fed in turn by three different combustion noise source terms which are obtained from the application of a statistical noise model on the RANS simulations and a post-processing of incompressible and compressible large eddy simulations (LES). In this way, the influence of the source model and acoustic solver is identified. The numerical results are compared with experimental data. In general, good agreement with the experiment is found for both the LOTAN and LNSE solvers. The LES source models deliver better results than the statistical noise model with respect to the amplitude and shape of the heat release spectrum. Beyond this, it is demonstrated that the phase relation of the source term does not affect the noise spectrum. Finally, a second simulation based on the inhomogeneous Helmholtz equation indicates the minor importance of the aerodynamic mean flow on the broadband noise spectrum.

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Some results in combustion generated noise

Cited by 16 publications

References 2 publications

Sound generation by turbulent premixed flames

Sound generation by turbulent premixed flames

Symmetry breaking of azimuthal thermo-acoustic modes in annular cavities: a theoretical study

Prediction of Combustion Noise in a Model Combustor Using a Network Model and a LNSE Approach

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