Dynamics of spray and swirling flame under acoustic oscillations : A joint experimental and LES investigation

Vignat, Guillaume; Schiavo, Ermanno Lo; Laera, Davide; Renaud, Antoine; Gicquel, Laurent; Durox, Daniel; Candel, Sébastien

doi:10.1016/j.proci.2020.05.054

Cited by 14 publications

(10 citation statements)

References 20 publications

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“…The results for the smaller recess distance are not shown here and are to be presented in a future article. The weak equivalence ratio fluctuation observed in the present case is also demonstrated through numerical simulations performed with a similar injector geometry in [57]. One may therefore assume for the present spray flame case, as for the premixed flames, that the light intensity of OH * is indicative of the heat release rate integrated over the flame volume Q.…”

Section: Discussionsupporting

confidence: 75%

Swirler effects on combustion instabilities analyzed with measured FDFs, injector impedances and damping rates

Soundararajan

Durox

Renaud

et al. 2022

Combustion and Flame

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Section: Discussionsupporting

confidence: 75%

Swirler effects on combustion instabilities analyzed with measured FDFs, injector impedances and damping rates

Soundararajan

Durox

Renaud

et al. 2022

Combustion and Flame

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“…In an experimental investigation of a premixed prevaporized combustor fed with heptane, Bernier et al [20] found that the evaporation delay happens simultaneously with droplet convection to the combustion region so that this delay need not be added to the other delays in the analysis of the causes of combustion instability. Vignat et al [9] used an LES to study a self-sustained combustion oscillation in a single injector test rig, namely SICCA-Spray, and reached a similar conclusion. However, this might not apply to fuels that are less volatile than heptane.…”

Section: Introductionmentioning

confidence: 76%

“…These engines when operated with liquid fuels, use spray atomizers. The spray can be strongly influenced by the acoustic pressure oscillations in the chamber, even if the high atomizing pressure ensures a constant flow rate in many configurations [6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Effect of Different Fuels on Combustion Instabilities in an Annular Combustor

Soundararajan

Vignat

Durox

et al. 2021

Journal of Engineering for Gas Turbines and Power

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Combustion instability in annular combustors of jet engines is a recurring issue. In the present study, the characteristics of instabilities for different fuels are investigated by combining the instability maps obtained in a laboratory-scale annular combustor equipped with multiple swirling spray injectors (MICCA-Spray) and flame describing functions (FDFs) from a single sector configuration (SICCA-Spray). Two types of liquid fuels are injected as hollow cone sprays: heptane, which is fairly volatile, and dodecane, which is less volatile. Experiments are also conducted with gaseous propane, premixed with air, which serves as a reference. An instability map is systematically drawn by varying the global equivalence ratio and thermal power. The data indicate that the amplitude and frequency of instabilities depend, for the same operating point, on the fuel injection conditions and fuel type. Overall trends show that premixed propane is unstable in a broad operating domain. Injection of liquid fuels induce changes in flame time lag that modify the unstable regions. For heptane, the instability map is closer to the propane reference map, whereas dodecane exhibits wider stable regions. An attempt is made to understand these features by examining the FDF, which gives the ratio of relative fluctuations in heat release rate to the relative fluctuations in velocity. The FDFs measured in a single sector configuration give access to gain and phase information that can be used to determine unstable bands and calculate an instability index guiding the interpretation of the differences in instabilities of the three fuels.

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“…• Finally, the same authors performed previous LES studies of the same system [28,29] revealing the coupling mechanism between the acoustic mode and the liquid film forming on the injector walls to be fundamental to trigger and sustain the thermoacoustic limit cycle. This conclusion however questions the impact of an injection angle variation which is expected to modify the liquid film and therefore its coupling with the thermoacoustic mode.…”

Section: Introductionmentioning

confidence: 91%

“…Finally, it is worth mentioning that, following previous works on the same configuration [28,29], the droplet size distribution is imposed via a Rosin-Rammler probability density function (PDF) fitted from experimental measurements of mean (D 10 ) and Sauter diameters (SMD or D 32 ) taken at z = 2.5 mm in the combustion chamber: D 10 = 10 µm and D 32 = 18 µm. Since the primary objective is to investigate only the effect of the spray angle, changes in terms of droplet diameter are only due to evaporation, neglecting phenomena like primary and secondary atomization as well as splash and liquid film break-up at the edge of the injector wall.…”

Section: Numerical and Experimental Setupmentioning

confidence: 99%

On the impact of fuel injection angle in Euler–Lagrange large eddy simulations of swirling spray flames exhibiting thermoacoustic instabilities

Schiavo

Laera

Riber

et al. 2021

Combustion and Flame

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This study deals with the fundamental problem of combustion dynamics in gas turbine combustors operating with liquid fuel. In this framework the present work proposes the study of an academic liquid fueled combustor sensitive to thermoacoustic instabilities, simulated via high-fidelity Large Eddy Simulations. The experimental setup addressed is SICCA-spray from EM2C laboratory featuring both stable and unstable flames depending on the combustion chamber length. The proposed analysis, based on the Euler-Lagrange modeling approach, studies the impact of the spray injection angle θ on both the stable flame and the triggering of the longitudinal combustor acoustic mode when using a longer quartz tube. For the liquid injection modeling, the FIM-UR semiempirical model is adopted with three different θ values: θ = 35 • , 45 • and 60 • . In stable conditions, the spray angle is proven to have a negligible impact on the flame anchoring point, however, the mean flame length and fuel distribution are found to be slightly modified by the velocity at which droplets enter the combustion chamber. For the thermoacoustically unstable conditions, two well-established stable limit cycles with the same frequency and similar amplitudes are obtained when fuel is injected at θ = 45 • and 60 • . Contrarily, the system stabilizes when θ = 35 • pointing to the importance of the dynamics of the liquid film layer formed inside the injector for this setup. Likewise, this liquid film layer dynamics and its modeling appear critical as already suggested by previous studies on the same configuration. The detailed analysis of the thermoacoustically unstable different predictions is then performed through the investigation of the spatial fields of the local Rayleigh index obtained following the novel extension in the frequency domain of the Rayleigh criterion complemented by the application of Dynamic Mode Decomposition. It confirms that the injection angle of the liquid spray has a significant effect on the thermoacoustic response of the system. Indeed the influence of θ on the dynamics of the liquid fuel when entering the combustion chamber is proven to have an impact on the synchronization mechanism governing the liquid phase with respect to acoustics sustaining the observed limit cycles. More specifically, couplings at the liquid phase level are evidenced by introducing two novel indices correlating the fluctuations of liquid fuel volume fraction and evaporation rate with pressure.

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Dynamics of spray and swirling flame under acoustic oscillations : A joint experimental and LES investigation

Cited by 14 publications

References 20 publications

Swirler effects on combustion instabilities analyzed with measured FDFs, injector impedances and damping rates

Swirler effects on combustion instabilities analyzed with measured FDFs, injector impedances and damping rates

Effect of Different Fuels on Combustion Instabilities in an Annular Combustor

On the impact of fuel injection angle in Euler–Lagrange large eddy simulations of swirling spray flames exhibiting thermoacoustic instabilities

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