Effects of Shear Layer Manipulation on Noise Emissions of a Turbulent Jet Flame

Nawroth, Holger; Paschereit, Christian Oliver

doi:10.2514/6.2015-0303

Cited by 3 publications

(3 citation statements)

References 18 publications

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“…Similar to previous studies (e.g., 24 ), the test rig ( Figure 1, left picture) consists of a combined fuel-air injector that leads to an annular injection manifold at the lower end, a middle section of constant diameter, and a quartz glass which provides optical access upstream of a converging nozzle. The rig is concluded with a pilot burner which has the same outlet diameter as the upstream nozzle (d=35mm).…”

Section: Methodsmentioning

confidence: 96%

“…This source of noise has been in the focus of academic research for a long time [4][5][6][7][8][9][10][11][12][13][14][15] and deals with noise generation within a flame which is caused by fluctuations in the velocity field of the incoming flow. Resulting spectra are of broadband character 14,19,24 and usually do not show distinct, combustion-related tonal peaks. Triggered by flow-induced fluctuations of the turbulent flow field, turbulent combustion leads to unsteady variations of the heat release rate.…”

Section: Introductionmentioning

confidence: 98%

“…In this paper, as a continuation of previous investigations 16- 19,24 the shear layer of an unconfined, turbulent reacting jet is deliberately manipulated. For this purpose, the incoming flow upstream of the burner outlet is tripped using zig-zag tape.…”

Section: Introductionmentioning

confidence: 99%

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Flow Fields of Manipulated Shear Layers of a Turbulent Jet Flame

Nawroth

Paschereit

2015

45th AIAA Fluid Dynamics Conference

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Noise emitted from a turbulent, premixed flame is investigated experimentally with a focus on the impact of the shear layer. For this purpose, the shear layer is altered by installing a tripping device upstream of the flame. Through artificially introduced turbulent fluctuations of the velocity within the shear layer, heat release rate fluctuations are increased, too. As these are the main source of direct combustion noise, sound pressure levels of reacting flows increase. Investigations reveal the impact of tripping location, equivalence ratio, and Reynolds number on noise emissions. At lean conditions and low Reynolds numbers, different tripping locations yield similar noise emissions whereas high Reynolds numbers lead to differences in noise emissions between locations. Higher equivalence ratios result in contrary findings, i.e., distinct differences between tripping locations for low Reynolds numbers, coinciding spectra for high Reynolds numbers. Nomenclature d = nozzle diameter f = frequency f s = sampling frequency n s = number of samples r/d = relative radial location with respect to nozzle diameter Re = Reynolds number SPL = sound pressure level T = preheat temperature u = axial velocity u rms = root-mean-square value of the axial velocity component v = radial velocity v rms = root-mean-square value of the radial velocity component x/d = relative axial location with respect to nozzle diameter x t /d = relative axial location of the tripping device with respect to nozzle diameter  = equivalence ratio of main reacting flow

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Section: Methodsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 98%

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Flow Fields of Manipulated Shear Layers of a Turbulent Jet Flame

Nawroth

Paschereit

2015

45th AIAA Fluid Dynamics Conference

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Fractal Characteristics of Combustion Noise

Saurabh

Imran

Nawroth

et al. 2018

Journal of Engineering for Gas Turbines and Power

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Fractal analysis is undertaken to characterize flame surface fluctuations on an unconfined turbulent premixed flame and the resulting far-field acoustics fluctuations. Results indicate that combustion noise is monofractal and is characterized by an anticorrelated structure with a Hurst exponent less than 0.5. The anticorrelated nature was identified in the pressure fluctuations as well as flame surface fluctuations for small time-scales. Additionally, results suggest that flame surface fluctuations are multifractal for large time scales. The calculated Hurst exponent increases noticeably with the equivalence ratio and decreases slightly with Reynolds number for the investigated operating conditions. Variation in the Hurst exponent for combustion noise data is compared with a case study of synthetic fluctuations comprised of linear combinations of white and 1/f2 noise. These results provide a more detailed characterization of the temporal structure of flame surface fluctuations and resulting noise emission from turbulent premixed flames than is presently known.

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High-Speed Flow Field Measurements of Turbulent Jet Flames Undergoing Shear Layer Manipulation

Nawroth

Paschereit

2016

54th AIAA Aerospace Sciences Meeting

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Effects of Shear Layer Manipulation on Noise Emissions of a Turbulent Jet Flame

Cited by 3 publications

References 18 publications

Flow Fields of Manipulated Shear Layers of a Turbulent Jet Flame

Flow Fields of Manipulated Shear Layers of a Turbulent Jet Flame

Fractal Characteristics of Combustion Noise

High-Speed Flow Field Measurements of Turbulent Jet Flames Undergoing Shear Layer Manipulation

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