Multi-Phase Combustion and Transport Processes Under the Influence of Acoustic Excitation

Wegener, Jeffrey

doi:10.21236/ad1005080

Cited by 7 publications

(7 citation statements)

References 89 publications

(211 reference statements)

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“…Although the contrast is weaker in the downstream region, the image fluctua-tions still represent the presence of structures that contain density differences. The preferred mode of the coaxial jet, based on the scaling law of Wegener 29 , is shown on the figure as the red vertical line and is near 1 kHz. The preferred mode estimate of 1 kHz is generally representative of lower frequency peaks at x/D 1 of seven and eight.…”

Section: Resultsmentioning

confidence: 99%

The Response of Cryogenic H2/O2 Coaxial Jet Flames to Acoustic Disturbances

Forliti

Badakhshan

Wegener

et al. 2015

53rd AIAA Aerospace Sciences Meeting

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An experimental study has been conducted to explore the coupling between a coaxial gaseous hydrogen / liquid oxygen jet flame and transverse acoustic perturbations. A variety of chamber conditions including acoustic frequency, amplitude, and the location of the pressure node / antinode with respect to the flame were examined. The flame response was documented using high-speed imaging including backlit visualization and unfiltered chemiluminescence. Dynamic mode decomposition was used to isolate the spatial structure of the flame response at the forcing frequency. The results indicate that the flame response to forcing is qualitatively similar to previous results of nonreacting coaxial jet flows; the pressure node forcing appears to generate in-plane flapping of the flame while pressure antinode forcing induces a helical structure in the flame.

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Section: Resultsmentioning

confidence: 99%

The Response of Cryogenic H2/O2 Coaxial Jet Flames to Acoustic Disturbances

Forliti

Badakhshan

Wegener

et al. 2015

53rd AIAA Aerospace Sciences Meeting

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“…There are somewhat larger increases observed for JP-8 and FT fuels than for alcohol fuels, but there does not appear to be a systematic dependence of K on frequency. In some cases, typically further away from the PN, the average K values during acoustic excitation fall slightly below the average unforced values (K unf ), but these typically lie within the average range of unforced burning rate constant values and their experimental uncertainties [46,73]. Hence, while the flame oscillations clearly differ for different frequencies of excitation, the influence of gravity on the burning droplet makes these differences less important for a global parameter such as the burning rate constant, at least for the moderate excitation amplitudes explored in Ref.…”

Section: Acoustically Coupled Fuel Droplet Combustion: Transient Procmentioning

confidence: 90%

“…2 Transactions of the ASME presence of soot in JP-8 and FT fuels is one of several differences between these fuels and alcohols; sooting is visible in these images due to the nature of the filters employed here [20,46]. Representative comparisons of average burning rate constants extracted from experiments involving nonfed (Eq.…”

Section: Single Fuel Droplet As a Basic Model For Condensed Phase Commentioning

confidence: 99%

“…Phase-locked OH* chemiluminescence imaging of the burning droplet under various operating conditions (forcing frequencies 332 Hz, 898 Hz, and 1500 Hz) incorporates an intensified CCD camera with a UV lens and camera photocathode. The imaging allows a combined transmission of the receiving optics [46,73] to lie primarily in the ultraviolet range 230-400 nm, thus capturing chemiluminescence of OH* in the heart of the flame zone at approximately 308 nm. In the facility shown in Fig.…”

Section: Acoustically Coupled Fuel Droplet Combustion: Transient Procmentioning

confidence: 99%

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Acoustically Coupled Combustion of Liquid Fuel Droplets

Karagozian

2016

Applied Mechanics Reviews

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The dynamics of oscillatory flames is relevant to acoustically coupled combustion instabilities arising in many practical engineering systems. This paper reviews fundamental studies that pertain to the combustion of single liquid fuel droplets in an acoustically resonant environment. This flow field is not only an idealized model for the study of the fundamental interaction of reactive, evaporative, acoustic, and other transport-based timescales, but it may also be used to identify relevant phenomena in more complex or practical geometries that require a focus for future combustion control efforts. The nature of these phenomena is discussed in detail, in addition to their implications for broader issues associated with combustion instabilities.

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“…The POD is calculated using singular value decomposition (SVD), the details of which can be found in Wegener. 27 The POD is applied to sets of 2000 images.…”

Section: American Institute Of Aeronautics and Astronauticsmentioning

confidence: 99%

Receptivity of a Cryogenic Coaxial Gas-Liquid Jet to Acoustic Disturbances

Wegener¹,

Forliti²,

Leyva³

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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An experimental study has been conducted at the Air Force Research Laboratory atEdwards Air Force Base to explore the receptivity of cryogenic coaxial jet flows to transverse acoustic disturbances. The shear coaxial jet flow employed liquid nitrogen in the inner jet and cooled helium in the outer annular jet to represent the nominal fluid dynamical conditions of an oxygen/hydrogen liquid rocket engine injector. The injector flow is submerged in a chamber that experiences a monotonic transverse acoustic resonance characteristic of a rocket chamber in the presence of combustion instability. The coaxial jet is exposed to a variety of acoustic conditions including different frequencies, amplitudes, and locations within the resonant mode shape. High-speed back-lit images were captured to record the behavior of the natural (unforced) and forced coaxial jets. Proper orthogonal decomposition and spectral analysis were used to extract natural and forced modes. Convective modes are extracted, and a new Strouhal number is used to characterize the dominant natural convective mode that is analogous to the preferred mode in free jets. The threshold of receptivity was found for a number of different injector flows and acoustic forcing conditions. The results indicate that the dimensionless frequency plays an important role, and there exists a finite forcing amplitude at which the threshold of receptivity occurs. The receptivity threshold and post receptivity response provides useful insight on the suitability of a given injector design for specific rocket combustion chamber conditions. NomenclatureAR = outer-to-inner area ratio c = speed of sound D = diameter f = frequency F = normalized frequency J = outer-to-inner momentum flux ratio m = mass p = pressure p' = pressure fluctuation amplitude St = Strouhal number t = inner jet post thickness U = mean velocity u' = velocity fluctuation amplitude ρ = density Subscripts c = convection meas = measured Dimotakis = the Dimotakis 1 convection velocity model 1 = inner jet fluid 2 = outer jet fluid

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Multi-Phase Combustion and Transport Processes Under the Influence of Acoustic Excitation

Cited by 7 publications

References 89 publications

The Response of Cryogenic H2/O2 Coaxial Jet Flames to Acoustic Disturbances

The Response of Cryogenic H2/O2 Coaxial Jet Flames to Acoustic Disturbances

Acoustically Coupled Combustion of Liquid Fuel Droplets

Receptivity of a Cryogenic Coaxial Gas-Liquid Jet to Acoustic Disturbances

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