Measurement and Analysis of Thermoacoustic Oscillations in a Simple Dump Combustor

Dawson, Scott T. M.; Fitzpatrick, Joan

doi:10.1006/jsvi.1999.2633

Cited by 12 publications

(3 citation statements)

References 13 publications

(12 reference statements)

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“…There is also significant energy in the measured temperature spectrum at low frequencies, which is most likely due to lowfrequency fluctuations in the heat release from the flame. Lowfrequency fluctuations were also seen in separate measurements of the heat release [12] and in the temperature measurements of Dawson and Fitzpatrick [23].…”

Section: Implementation Of the 2m1t Methodsmentioning

confidence: 94%

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Comparison of Open and Choked Premixed Combustor Exits During Thermoacoustic Limit Cycle

Hield

Brear

2008

AIAA Journal

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This paper compares the thermoacoustic limit cycles of a premixed laboratory combustor with acoustically open and choked exits. It is shown that the form of the downstream boundary condition can have a significant effect on the combustion chamber acoustics, with both the dominant limit cycle frequencies and the acoustic mode shapes being very different for the different combustor exits. The fundamental limit cycle frequency with the choked exit in place agrees closely with that determined by the convective time scales of entropy disturbances, as argued by other authors. A novel experimental method is then developed to examine the acoustic response of an arbitrary duct termination to incident pressure and entropy perturbations, and used to measure the response of the combustor downstream boundary condition during thermoacoustic limit cycle. The reflection coefficient for the acoustically open exit matches closely the classical result for zero mean flow. It is also shown that a choked nozzle downstream of the flame generates significant sound due to the interaction of the convected entropy perturbation with the nozzle. This final result is qualitatively in keeping with an existing analytic boundary condition for a choked nozzle, even though quantitative agreement is not observed. Reasons for this discrepancy are then suggested. Nomenclature A = Fourier transform of the nondimensional incident pressure fluctuation AR = downstream nozzle area ratio a = amplitude of the incident nondimensional pressure fluctuation B = Fourier transform of the nondimensional reflected pressure fluctuation b = amplitude of the reflected nondimensional pressure fluctuation C ij = real part of the cross-spectral density between i and j c = speed of sound c p = specific heat at constant pressure f = frequency H = transfer function k = wave number L = length of rig downstream of the flame holder M = Mach number n = mode number P = Fourier transform of the nondimensional pressure fluctuation p = pressure Q ij = imaginary part of the cross-spectral density between i and j R = reflection coefficient S = Fourier transform of the nondimensional entropy fluctuation S ij = cross-spectral density between i and j s = entropy, amplitude of the nondimensional entropy fluctuation T = temperature, Fourier transform of the nondimensional temperature, measurement period t = time u = velocity x = spatial coordinate = ratio of specific heats = density = equivalence ratio ! = angular frequency Subscripts H = hot flow quantity i = incident n = mode number p = pressure r = reflected s = entropy 1,2,. . . = measurement location, transfer function number Modifiers g = mean component of the quantity g g 0 = fluctuating component of the quantity g g = complex conjugate of the complex number g

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Section: Implementation Of the 2m1t Methodsmentioning

confidence: 94%

“…Figure 5 shows a cross-sectional view of the thermocouple mount and a photograph of the thermocouple tip. A similar thermocouple was used by Dawson and Fitzpatrick [23] to measure the temperature spectrum downstream of the flame in a dump combustor during thermoacoustic instability.…”

Section: Implementation Of the 2m1t Methodsmentioning

confidence: 99%

Comparison of Open and Choked Premixed Combustor Exits During Thermoacoustic Limit Cycle

Hield

Brear

2008

AIAA Journal

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“…A similar analysis shows that the fractional density and temperature fluctuations are also small in comparison to the fractional velocity fluctuations. Thus, as is commonly done in studies of premixed combustion, it is reasonable to assume that the acoustic velocity fluctuations are the main excitation of the heat release fluctuations in the flame, and to neglect the effect of the fluctuations in other quantities [2,4,13,14,31,[37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Thermoacoustic limit cycles in a premixed laboratory combustor with open and choked exits

Hield

Brear

Jin

2009

Combustion and Flame

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Investigation of self-excited combustion instabilities in two different combustion systems

Seo

2004

KSME International Journal

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Measurement and Analysis of Thermoacoustic Oscillations in a Simple Dump Combustor

Cited by 12 publications

References 13 publications

Comparison of Open and Choked Premixed Combustor Exits During Thermoacoustic Limit Cycle

Comparison of Open and Choked Premixed Combustor Exits During Thermoacoustic Limit Cycle

Thermoacoustic limit cycles in a premixed laboratory combustor with open and choked exits

Investigation of self-excited combustion instabilities in two different combustion systems

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