Acoustic and disturbance energy analysis of a flow with heat communication

Karimi, Nader; Brear, Michael J.; Moase, William H.

doi:10.1017/s0022112007009573

Cited by 52 publications

(56 citation statements)

References 24 publications

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“…This causes reflection of the incident acoustic wave [40] which in turn intensifies the deviation from the theoretical assumptions. Most importantly, it has been shown that such reflection is more significant at low frequencies [9,10]. Therefore, particularly at low frequencies, it sounds plausible to expect the flow field on the flame surface to be more complicated than that assumed by the theory.…”

Section: Comparison With the Constant Phase Speed Theorymentioning

confidence: 99%

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Response of a conical, laminar premixed flame to low amplitude acoustic forcing – A comparison between experiment and kinematic theories

Karimi

2014

Energy

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This paper presents an experimental study on the dynamics of a ducted, conical, laminar premixed flame subjected to low amplitude acoustic excitation from upstream. The heat release response of the flame to velocity disturbances is investigated through measurement of the so called 'flame transfer function' for a wide range of forcing frequencies. The results are compared with those predicted by the existing linear kinematic theories. It is observed that these theories are in general agreement with the experiment, although there exist some disparities. A detailed comparison of the experimental data with the kinematic theories shows that the phase speed of flame disturbances has an essential influence upon the level of agreement between the theory and experiment. The data set presented in this work complements that reported in an earlier study. In keeping with others, visualisation of the excited flames clearly shows that the flame response includes waves on the flame front which are formed at the base and then convect along the flame.

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Section: Comparison With the Constant Phase Speed Theorymentioning

confidence: 99%

“…Further, the essential physics of thermoacoustic instabilities are not entirely understood [6,7]. This is mostly due to the complexities involved in the interactions between premixed flames and sound waves [9,10] and, to some extent, the effects of system boundaries [11,12].…”

Section: Introductionmentioning

confidence: 99%

Response of a conical, laminar premixed flame to low amplitude acoustic forcing – A comparison between experiment and kinematic theories

Karimi

2014

Energy

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“…Decomposition of the thermodynamic properties into steady and perturbation components and a subsequent linearization of Gibbs and ideal gas relations results in the following equations [10,32] …”

Section: Problem Configuration and Boundary Conditionsmentioning

confidence: 99%

“…Further, most recent studies have shown that entropy waves do not necessarily propagate as passive scalars and can affect the base flow [31]. It is, therefore, unclear if the conventional onedimensional, passive scalar treatment is always representative of the real entropy waves [32,33]. Besides, currently there is limited understanding of the decay of amplitude or dissipation of entropy waves as they travel from the reactive region to the exit nozzle of the combustor.…”

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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“…Transfer of heat can also modify acoustic and entropic waves. Further, it can affect the velocity field in compressible flows and therefore leaves an indirect influence on the acoustic waves [13,14]. It follows that these should be, therefore, involved in a realistic model of noise generation in nozzles.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the transmitted noise of a combustor exit nozzle caused by burned hydrogen-hydrocarbon gases

Hosseinalipour

Fattahi

Karimi

2016

International Journal of Hydrogen Energy

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Transmitted noise is a major problem in industrial and aero-engine gas turbines. One of a noise generating part in the preceding systems is exit nozzle which can play as encouraging or discouraging sound waves. The generated noise may arise from an incident acoustic wave or entropy wave. In this paper, the effect of heat transfer and inlet Mach number of the exit nozzle as well as replacing the traditional hydrocarbon fuels with hydrogen and composite of hydrogen-hydrocarbon on noise generation is studied. Further, the influence of the hydrodynamic decaying mechanisms in a nozzle on the noise generated by entropy waves is investigated. It is found that hydrogen can reduce transmitted noise in a subcritical nozzle with an acoustic incident wave or in a supercritical nozzle with an incident entropic wave.

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Acoustic and disturbance energy analysis of a flow with heat communication

Cited by 52 publications

References 24 publications

Response of a conical, laminar premixed flame to low amplitude acoustic forcing – A comparison between experiment and kinematic theories

Response of a conical, laminar premixed flame to low amplitude acoustic forcing – A comparison between experiment and kinematic theories

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

Investigation of the transmitted noise of a combustor exit nozzle caused by burned hydrogen-hydrocarbon gases

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