Liquid-Fuel Behavior in an Aeronautical Injector Submitted to Thermoacoustic Instabilities

Apeloig, Julien; d'Herbigny, François-Xavier; Simon, Frank; Gajan, Pierre; Orain, Mikaël; Roux, Sébastien

doi:10.2514/1.b35290

Cited by 29 publications

(14 citation statements)

References 41 publications

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“…The experimental setup dimensions and the flow conditions were chosen to reproduce the main phenomena observed by Apeloig et al [15] within the injection system and described in the introduction. Therefore, the Weber number ensures an equivalent atomization regime while both the momentum flux ratio and the channel height allow the observation of periodic liquid impacts on the upper wall.…”

Section: Experimental Approachmentioning

confidence: 99%

“…More recently, Apeloig et al [15] studied the unsteady interaction of a kerosene spray downstream from a multi-point injector with flame. The injection system comprised two injection zones, a pilot zone with a pressure atomizer at the center and a multipoint zone at the periphery.…”

Section: Introductionmentioning

confidence: 99%

“…Apeloig showed that these unsteady phenomena are at the origin of heat release fluctuations measured in the flame. From the analysis of these image sequences, Apeloig et al [15] proposed that the droplet flux oscillations are linked to a periodic bending of the individual liquid fuel columns inside the injector, induced by the local air velocity fluctuations. In particular, depending on the instantaneous liquid-to-air momentum flux ratio, each liquid jet may impact the opposite injector wall forming a liquid film, which is atomized further downstream at the injector outlet.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Confined Liquid Jet Injected into Oscillating Air Crossflow

Bodoc

Desclaux

Gajan

et al. 2019

Flow Turbulence Combust

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The aim of this work is to study the role of the liquid phase in the thermo-acoustic coupling that leads to combustion instabilities. In multipoint injection systems, the liquid fuel is injected through orifices as jets which are destabilized by the high-speed air flowing in a transverse direction. This paper is focused on the effect of an acoustic excitation imposed on the air flow on the various liquid features observed in actual fuel injection systems. This concerns the initial jet trajectory, its breakup, the formation and transport of the resulting spray, the liquid film formation on walls and its final atomization at the outlet of the injection system. Experimental investigations were performed on a simplified geometry designed to reproduce these main phenomena. Phaseaveraged processing of the experimental data is used to analyze the relationship between the acoustic excitation and the liquid phase behavior. In particular, the phase delays imposed by the various processes involved are analyzed. The processing of high-speed video recordings reveals harmonic oscillation of the liquid column which periodically breaks into a spray structure or impacts the opposite wall, forming a liquid film. Using PDA measurements, it is shown that the resulting two-phase flow consists of alternating dense and diluted zones transported by the air flow. At the end of the channel, the liquid film flowing on the wall opposite the liquid jet is periodically atomized through the oscillating shear forces imposed by the air flow.

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Section: Experimental Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Confined Liquid Jet Injected into Oscillating Air Crossflow

Bodoc

Desclaux

Gajan

et al. 2019

Flow Turbulence Combust

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“…For reduction of NOx from aircrafts, coaxial-staging lean burn fuel injection systems have been studied intensively these days [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and some of them have been already in service. Typically, they consist of a non-premixedmode pilot nozzle at the center for flame stability and a lean premixed-mode main nozzle surrounding the pilot for drastic NOx reductions.…”

Section: Introductionmentioning

confidence: 99%

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

Matsuura

Uesaka

Iwasaki

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The visualization of the pilot flame of a coaxially-staged aero-engine lean-burn fuel injector, not only downstream but also inside of the pilot nozzle, was successfully performed at realistic aero-engine conditions. Optical access toward the inside of the nozzle was achieved through the inner and outer shrouds, both of which were made of transparent quartz. The image distortion caused by complex contours of the two shrouds was corrected by a method based on optical ray tracing, which realized precise determination of spatial intensity distribution of optical signals. Line-of-sight OH chemiluminescence, cross-sectional OH-LIF, kerosene LIF and kerosene Mie scattering were employed as diagnostic tools. The effects of pilot local air-to-fuel ratio on spray flame structure were revealed, both inside and downstream of the pilot nozzle under stable combustions. As the pilot mixture got rich, the main reaction zone moved from inside of the pilot nozzle to the region near the injector lip downstream of the injector exit. The OH-LIF signal was detected near the central axis surrounded by the fuel spray. It was also observed near the back-step of the pilot nozzle for the rich cases. The experiments under combustion oscillation were also conducted and the correlation of phenomena inside and downstream of the pilot nozzle was captured. It was clarified that the reaction enhancement in the outer part of the lip vortex region was caused by the convection of rich mixture, which appeared near the pilot atomizer lip at 150~210deg earlier oscillation phase angle. KeywordsAero-engine combustor, Optical burner/injector, Staged lean-burn injector, Laser induced fluorescence, Ray tracing, Optical refraction correction, Elevated temperature and pressure IntroductionFor reduction of NOx from aircrafts, coaxial-staging lean burn fuel injection systems have been studied intensively these days [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and some of them have been already in service. Typically, they consist of a non-premixedmode pilot nozzle at the center for flame stability and a lean premixed-mode main nozzle surrounding the pilot for drastic NOx reductions. For such an injector, both fuel injection and fuel/air mixing start a few centimeter upstream from the injector exit (i.e. entrance of the combustion chamber). Moreover, this is also true for its pilot flame. Therefore, many important phenomena take place in regions enclosed by the metal walls of the injector, where the application of optical diagnostics is not straightforward compared with a conventional combustor. In our previous work, visualization of fuel spray/vapor behavior and fuel/air mixing inside the main nozzle (i.e. the premixing duct) was performed by high speed visualization and/or LIF techniques [10,11,15]. Through a fullycontoured quartz-made transparent outer-shroud, dynamic motion of fuel sprays under combustion oscillations at an elevated pressure and temperature was clearly captured and discussed in relation to the flame dynamics downstream [15]. ...

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“…12. Potential candidates for this non-linear effect could be vortex shedding [29] and liquid fuel fluctuations [30]. The first phenomenon could indeed play a role in the instability even from very low amplitudes at the 473 Hz frequency.…”

Section: Pressure and Heat Release Fluctuationsmentioning

confidence: 99%

Experimental Study of Thermo-Acoustic Instability Triggering in a Staged Liquid Fuel Combustor Using High-Speed OH-PLIF

Renaud

Tachibana

Arase

et al. 2018

Journal of Engineering for Gas Turbines and Power

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A staged injector developed by JAXA and fueled with kerosene is studied in a high-pressure combustion experiment. With a stable pilot fuel flow rate, the fuel flow rate in the main stage is progressively increased. A high-speed OH-PLIF system is used to record the flame motion at 10,000 fps. In the beginning of the recording, the flame behavior is dominated by relatively low-frequency rotation due to the swirling motion of the flow. These rotational motions then coexist with a thermo-acoustic instability around 475 Hz which increases the amplitude of the pressure fluctuations inside the chamber. DMD analyses indicate that this instability is associated with a widening of the flame occurring when the pressure fluctuations are the highest, giving the instability a positive feedback. The instability frequency then abruptly switches to 500 Hz while the mode shape remains

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Liquid-Fuel Behavior in an Aeronautical Injector Submitted to Thermoacoustic Instabilities

Cited by 29 publications

References 41 publications

Characterization of Confined Liquid Jet Injected into Oscillating Air Crossflow

Characterization of Confined Liquid Jet Injected into Oscillating Air Crossflow

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

Experimental Study of Thermo-Acoustic Instability Triggering in a Staged Liquid Fuel Combustor Using High-Speed OH-PLIF

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