Combustion noise

Dowling, Ann P.; Mahmoudi, Yasser

doi:10.1016/j.proci.2014.08.016

Cited by 280 publications

(197 citation statements)

References 120 publications

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“…This is partially because advances in the design of aircraft have reduced other noise sources such as jet, fan and external aerodynamic noise [1,2]. Furthermore, modern low-NOx combustors show a considerable increase in noise emission [3].…”

Section: Introductionmentioning

confidence: 99%

“…This noise propagates from the combustion chamber through the turbine and jet to the far field. The 'indirect' combustion noise is ________________________ 1 Research Associate, Department of Engineering, Trumpington Street. 2 Professor, Department of Engineering, Trumpington Street.…”

Section: Introductionmentioning

confidence: 99%

“…It is often called 'entropy noise' and was first investigated analytically at low Mach numbers by the early works of Marble & Candel [6] and Morfey [8] in the seventies. Combustion noise has been found to be important at low frequencies [9] and in the gas turbine geometry indirect noise dominates direct combustion noise at low frequencies [1,10,11].In a detailed review by Morgans and Duran [12], five stages of flow physics have been identified as being important for entropy noise in gas turbines. These being (1) generation of entropy waves by unsteady heat release rate; (2) advection of entropy waves through the combustor (3) acceleration of entropy waves through nozzle guide vane and turbine blade rows that generates entropy noise (4) passage of entropy noise through a succession of turbine blade rows to appear at the turbine exit and (5) reflection of entropy noise back into the combustor, where it may further perturb the flame, causing the combustor thermoacoustic instability.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic and Entropy Waves in Nozzles in Combustion Noise Framework

2017

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A low-order model is presented to study the propagation and interaction of acoustic and entropic perturbations through a convergent-divergent nozzle. The calculations deal with choked, unchoked, as well as compact and non-compact nozzles. In the choked case, a normal shock exists in the divergent section of the nozzle. To validate the models developed, cylindrical configurations corresponding to Entropy-WaveGenerator (EWG) and Hot-Acoustic-Testrig (HAT) of DLR are studied. For the EWG, an entropy wave is generated upstream of a nozzle by an electrical heating device, and for the HAT a speaker is used to generate pressure waves. In these two configurations and for the choked case, the supersonic region between the nozzle throat and the normal shock is assumed to be acoustically compact. The results of the low-order model are found to give excellent agreement with the experimental results of the EWG and HAT rigs. To give insight into the physics, the model is used to undertake a parametric study for a range of nozzle lengths and shock strengths. The low order model is finally used to calculate the direct to indirect (entropy and vorticity) combustion noise ratio for an idealised thin-annular combustor. For this model combustor the direct acoustic noise is found to dominate within the combustor while, the entropy indirect noise is found to be the main source of noise downstream of the choked nozzle. The indirect vorticity noise has a negligible contribution.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acoustic and Entropy Waves in Nozzles in Combustion Noise Framework

2017

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“…Note that the entropy wave upstream of the flame, E 1 , can be assumed to be zero, but the flame generated entropy wave which propagates to the combustor outlet needs to be considered [27,28]. Predictions of the system's thermoacoustic modes are compared using both the present HR model and previous HR models assuming continuous stagnation enthalpy to investigate the effect on the thermoacoustic modes.…”

Section: The Effect On Thermoacoustic Modesmentioning

confidence: 99%

“…the acoustic reflection (generation) coefficient due to the entropy wave -this reflected acoustic is also called the entropy noise [27,28,31].…”

Section: Ivb Closed-choked Combustormentioning

confidence: 99%

Acoustic Models for Cooled Helmholtz Resonators

Yang

Morgans

2017

AIAA Journal

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Combustion‐Generated Noise: An Environment‐Related Issue for Future Combustion Systems

et al. 2017

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A first‐order estimation of the prediction of combustion‐generated noise from turbulent premixed flames was explored. The method was based on Lighthill's acoustic analogy and used measurement data from high‐speed imaging of chemiluminescent emissions as input. To determine the noise‐generating source, that is, the overall heat release rate from the measured chemiluminescence signals, numerical simulations were performed for 1 D laminar and 3 D turbulent freely propagating flames by employing detailed transport models and reaction mechanisms, including the full reaction chain of the electronically excited hydroxyl radical (OH*). It was shown for both the 1 D and 3 D cases that the local generation of OH* correlated strongly with the heat released from the chemical reaction, especially in the fuel‐lean range. As the chemiluminescence measurements gathered light only along the viewing direction, the line‐of‐sight summed values of heat release rate and OH* concentration were evaluated from the 3 D simulation, and a quasilinear relationship was identified for these integral values. Hence, a proportionality relation was applied for computation of the integral heat release from measured chemiluminescence intensity. An analytical solution of Lighthill's wave equation served as a transfer function, which took fluctuations in the total heat release rate or light intensity as input to calculate the sound radiation in the far field. This approach was applied to a generic burner operated with premixed methane/air jet flames. Good quantitative agreement was obtained between the sound pressures derived from the chemiluminescence measurements and the microphone data, which highlights the potential of the method for applications to more complex flame configurations.

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Combustion noise

Cited by 280 publications

References 120 publications

Acoustic and Entropy Waves in Nozzles in Combustion Noise Framework

Acoustic and Entropy Waves in Nozzles in Combustion Noise Framework

Acoustic Models for Cooled Helmholtz Resonators

Combustion‐Generated Noise: An Environment‐Related Issue for Future Combustion Systems

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