Noise Generation by Open Turbulent Flames

Smith, Timothy; Kilham, J.K.

doi:10.1121/1.1937024

Cited by 30 publications

(34 citation statements)

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“…The total noise outputs of premixed flames have been systematically investigated as a function of pilot mass flow rate by Smith and Kilham (1963). The noise amplitude of the cold flow, flow with pilot flame, and the fully stabilized flame have been systematically investigated by Shivashankara, et a1.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

“…Here, we restrict ourselves to the noise problem, where many aspects of the problem have been clarified in recent times (Strahle and coworkers 1971,,;, Smith and Kilham 1963, Kotake and Hatta 1965, Knott 1971, Hurle, et al 1968, Giammar and Putnam 1970. An examination of the literature indicates that the following points are fairly clear.…”

Section: Introductionmentioning

confidence: 99%

“…Kotake and Hatta (1965) and Smith and Kilham (1963) have found the Strouhal number at the center frequency to be reasonably constant, indicating a simple "geometrical" mechanism for noise production in flames. On the other hand, Shivashankara, et al (1973) do not find this simple picture to be valid and state " ... it appears quite improper to try to use Strouhal Number to nondimensionalize combustion noise peak frequencies ... ".…”

Section: Introductionmentioning

confidence: 99%

“…Smith and Kilham (1963), in their tests on premixed flames of propane, ethylene, and methane with air, found that the acoustic power was proportional to (UDS h )2 for stoichiometric jet flames. Kotake and Hatta (1965), in their premixed diffusion flames (partly premixed and the rest non-premixed), found that the intensity of the noise output in jet flames was proportional to U 2 at low velocitie s and to U 4 at high velocities.…”

Section: Introductionmentioning

confidence: 99%

“…For example, the mechanism of anchoring the flame may have a strong influence on the noise output. Smith and Kilham (1963) made a systematic investigation of the noise output from the main flame as affected by the pilot flame mass output and found regions where the pilot flame apparently does not affect the acoustic power of the main flame. Shivashankara, et al (1973) Many associated experiments are also possible.…”

Section: Introductionmentioning

confidence: 99%

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Further experimental results on the structure and acoustics of turbulent jet flames

Kumar

1975

2nd Aeroacoustics Conference

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The structure of open turbulent jet flames is experimentally studied in the context of their noise emission characteristics. The differences between premixed and (co-flow) non-premixed flames are explored. Recent experiments repeated in an anechoic chamber complement earlier results obtained in a hard-walled bay. The reactants (methane and enriched air) are burned in the premixed, or non-premixed, mode after a length of pipe flow (t/D> 150). The thick-walled tubes anchor the flames to the tip at all of the velocities employed (maximum velocity, well over 300 ft/sec), thus eliminating uncertainties associated with external flameholders. The time-averaged appearance of the flames is obtained with still photographs (1160 sec). The detailed structures are revealed through high-speed ("" 2500 frames/sec) motion pictures. The acoustic outputs of the flames are mapped with a condenser microphone. The recorded data are played back to obtain the amplitude, waveshapes, directionalities, and frequency spectra of the noise. Profound differences are found between the premixed and non-premixed flames in their structures and noise characteristics.

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Section: Interpretation and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Further experimental results on the structure and acoustics of turbulent jet flames

Kumar

1975

2nd Aeroacoustics Conference

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Spatial Coherence of the Heat Release Fluctuations in Turbulent Jet and Swirl Flames

Wäsle

Winkler

Sattelmayer

2005

Flow Turbulence Combust

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The noise generation of turbulent flames is governed by temporal changes of the total flame volume due to local heat release fluctuations. On the basis of the wave equation an expression for the relationship between the acoustic power and the heat release fluctuations is derived and a correlation function is obtained which reveals that the sound pressure level of flames is governed by the spatial coherence. Noise models rely on precise coherence information in terms of characteristic length scales, which are the measure of the acoustic efficiency of the flame. Since the published length scale information is scarce and inconsistent, length scales were measured for a number of laboratory flames using two measurement techniques developed for this purpose: A planar LIF-system with a repetition rate of 1 kHz acquires the instantaneous flame front position and heat release, whereas two chemiluminescence probes with an optics confining the measurement volume to a line of sight provide further spatial correlation data. For all flames investigated the length scales are smaller than the height of the burner exit annulus and they are of the order of the local flame brush thickness. Using the measured length scales, the coherent volume and the efficiency of the noise generation are calculated, which are three orders of magnitude higher than measured. However, the proper order of magnitude is obtained, if only the measured fluctuating part of the thermal power is used in the model and if the periodic formation of local zones with heat release overshoot and deficit are properly incorporated. Nomenclature A = Surface (m 2 ) c = Acoustic velocity (m/s) c p = Specific heat capacity (J/(kg K)) D = Diameter of the nozzle (m) D lance = Lance diameter (m) f = Frequency (Hz) h 0 k = Enthalpy of formation of species k (J/kg) h slot = Slot height of the burner nozzle (m) I = Acoustic intensity (Pa/m 2 ) K per = Correction factor for periodic effects (−) L = Length scale (m) Ma = Mach number (−) 30 J. WÄSLE ET AL. n = Number of species (−) N = Number of incoherent volumes (−) p = Pressure (Pa) p = Pressure fluctuation (Pa) P thermal = Thermal power (W) P ac = Acoustic power (W) q = Volumetric heat release fluctuation (W/m 3 ) Q = Heat release fluctuation (W) r = Radial direction, distance (m) r 0 = Intersection radius with abscissa (m) R = Gas constant (J/(kg K)) R i j = Correlation coefficient (−) Re = Reynolds number (−) s = Arbitrary signal s ac = Acoustic source (J/m 3 ) S = Swirl number (−) t = Time (s) T = Temperature (K) T i j = Lighthill's stress tensor (kg/(m s 2 )) u = Velocity (m/s) u = Velocity fluctuation, sound particle velocity (m/s) V = Volume (m 3 ) x = Distance between sources (m) x 0 = Position of observer (m) x s = Position of source (m) z = Axial direction (m) Z = Acoustic impedance (kg/(m 2 s)) Greek Letters γ = Relation of specific heat capacity (−) i j = Correlation function (−) * = Cross correlation function of the acoustic sources (J 2 /m 6 ) η = Efficiency (−) ρ = Density (kg/m 3 ) ρ e = Excess density (kg/m 3 ...

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Noise sources in turbulent gaseous premixed flames

Roberts

Leventhall

1973

Applied Acoustics

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Noise Generation by Open Turbulent Flames

Cited by 30 publications

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Further experimental results on the structure and acoustics of turbulent jet flames

Further experimental results on the structure and acoustics of turbulent jet flames

Spatial Coherence of the Heat Release Fluctuations in Turbulent Jet and Swirl Flames

Noise sources in turbulent gaseous premixed flames

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