Influence of Random Excitations on Acoustic Instabilities in Combustion Chambers

Burnley, V.; Culick, F. E. C.

doi:10.2514/2.1116

Cited by 46 publications

(10 citation statements)

References 16 publications

(16 reference statements)

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“…In turbulent combustors, the thermoacoustically stable state is characterised by combustion noise, which is generated by turbulent reacting flow, has broadband characteristics, and is often assumed to be stochastic (Clavin et al, 1994;Burnley & Culick, 2000;Lieuwen, 2002). Lieuwen & Banaszuk (2005) consider noise to be forcing of the dynamical system (additive noise) or fluctuation of the system's parameters (parametric noise).…”

Section: Stochastic Approachmentioning

confidence: 99%

Sensitivity and Nonlinearity of Thermoacoustic Oscillations

Juniper

Sujith

2018

Annu. Rev. Fluid Mech.

257

178

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Nine decades of rocket engine and gas turbine development have shown that thermoacoustic oscillations are difficult to predict, but can usually be eliminated with relatively small ad hoc design changes. These changes can, however, be ruinously expensive to devise. This review explains why linear and nonlinear thermoacoustic behaviour is so sensitive to parameters such as operating point, fuel composition, and injector geometry. It shows how non-periodic behaviour arises in experiments and simulations and discusses how fluctuations in thermoacoustic systems with turbulent reacting flow, which are usually filtered or averaged out as noise, can reveal useful information. Finally, it proposes tools to exploit this sensitivity in the future: adjoint-based sensitivity analysis to optimize passive control designs, and complex systems theory to warn of impending thermoacoustic oscillations and to identify the most sensitive elements of a thermoacoustic system.

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Section: Stochastic Approachmentioning

confidence: 99%

Sensitivity and Nonlinearity of Thermoacoustic Oscillations

Juniper

Sujith

2018

Annu. Rev. Fluid Mech.

257

178

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“…The total acoustic power P ac emitted from a turbulent reacting jet can be estimated as (19) and the rate at which chemical and kinetic energy are supplied to the jet can be computed from…”

Section: Far-field Approximation and Acoustic Powermentioning

confidence: 99%

“…In this respect, the broadband acoustic perturbations interact only weakly with the heat release rate, so that this process is often considered to be passive [17]. However, theoretical analyses showed that noise in enclosed combustion systems, for instance in gas turbines and advanced low-emission aircraft engines [6], plays a critical role as precursor for combustion instabilities [18,19], and even such weak interactions can trigger thermoacoustic instabilities, in which the flame becomes an active part of the acoustic system [20,21,22].…”

Section: Introductionmentioning

confidence: 99%

On the Generation of Direct Combustion Noise in Turbulent Non-Premixed Flames

Ihme

Pitsch

2012

International Journal of Aeroacoustics

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Generation of combustion noise in an unconfined turbulent non-premixed flame is investigated. For this, a model is developed, combining Lighthill's acoustic analogy with a flameletbased combustion model to consistently express all thermochemical quantities by a set of reduced scalars. The model is applied in a large-eddy simulation, and the acoustic pressure in the far field is obtained from an integral solution. Three relevant acoustic source terms with different source characteristics and Mach number scaling are identified. The spatial distribution and spectral characteristics of the acoustic sources are analyzed, and it is shown that the acoustic source due to chemical reaction is the main noise contributor, and is located in the upper part of the flame. Contributions from the acoustic sources due to Reynolds stresses and fluctuating mass flux are found to be virtually insignificant at low frequencies. Discrepancies in the prediction of high-frequency sound pressure level in the jet forward direction were analyzed and are attributed to high-frequency acoustic refraction effects due to variations in sound speed. The directivity exhibits a weak directionality in the 30°forward direction, and some phase cancellation between individual acoustic sources is evident.

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“…Although dependent on engine configuration and operating regime, these direct core noise contributions typically fall in the low-frequency range, corresponding to the 200-400 Hz frequency band. 16,17 In this context it is also noted that these direct noise-sources can act as a bypass mechanism to excite thermo-acoustic instabilities in the combustor, [18][19][20][21] and even relatively weak interactions can trigger combustion instabilities. 22 Apart from combustion-generated pressure perturbations, the unsteady combustion process generates velocity and entropy fluctuations that exit the combustor, and are convected to the nozzle.…”

Section: Precursors For Instabilitiesmentioning

confidence: 99%

Jet Noise Receptivity to Nozzle-upstream Perturbations in Compressible Heated Jets

See

Amini

Koh

et al. 2012

18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference)

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Effects of nozzle-upstream entropy perturbations on the acoustic radiation from heated jets are investigated. For this, a model problem is considered, in which a gas-turbine combustor discharges reaction products through a converging nozzle into the ambient environment. The turbulent reacting flow field in the combustor is computed using large-eddy simulation (LES), and the unsteady flow-field at the combustor exit is extracted to provide realistic inflow conditions to the jet-flow simulation. To study the indirect coupling process, arising from the interaction of the combustion-generated entropy fluctuations with the adverse pressure gradient through the nozzle, a linearized Euler formulation is employed. Parametric studies are performed to investigate effects of frequency and amplitude of the nozzle-upstream entropy perturbations on the jet instability and the jet noise directivity. Simulation results show that the directivity is dependent on the perturbation frequency. Excitation near the preferred shear-layer instability leads to strong acoustic radiation in the 45 • forward direction, and the radiation angle decreases with decreasing excitation frequency.

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Influence of Random Excitations on Acoustic Instabilities in Combustion Chambers

Cited by 46 publications

References 16 publications

Sensitivity and Nonlinearity of Thermoacoustic Oscillations

Sensitivity and Nonlinearity of Thermoacoustic Oscillations

On the Generation of Direct Combustion Noise in Turbulent Non-Premixed Flames

Jet Noise Receptivity to Nozzle-upstream Perturbations in Compressible Heated Jets

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