Comparison of Center Nozzle Staging to Outer Nozzle Staging in a Multi-Flame Combustor

Culler, Wyatt; Chen, Xiaoling; Peluso, Stephen; Santavicca, Domenic A.; O’Connor, Jacqueline; Noble, David R.

doi:10.1115/gt2018-75423

Cited by 5 publications

(9 citation statements)

References 17 publications

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“…The intermittent formation of small-scale vortices, such as those shown on the RL branch during right-nozzle staging in Figure 5, contributes to the presence of outliers in Figure 8. The presence of strong edge oscillation coherence and persistent pressure intermittency in the right-nozzle staged operating mode are further evidence that the aforementioned damped coherent oscillation state [22] has been reproduced.…”

Section: Quantification Of Flame Dynamicsmentioning

confidence: 67%

“…We have previously shown that the in-phase oscillation of adjacent flames in the unstable regime suggests the presence of largescale, coherent vortical structures that convect downstream from the combustor dump plane [21]. Examination of local instantaneous heat release rate phase via chemiluminescence imaging showed these oscillations to occur in-phase with dynamic pressure sampled at the dump plate [22], illustrating two components of the instability feedback loop. In the stable regime, the staged flame seemed to oscillate out of phase with the other flames, as evidenced by a shift in the local phase oscillations of adjacent flames and a significant reduction in the pressure fluctuation amplitude [9].…”

Section: Introductionmentioning

confidence: 89%

“…In this work, we utilize OH-PLIF and an edge tracking algorithm to investigate the previously proposed hypothesis that fuel staging suppresses instability via flame oscillation phase cancellation. We consider two casesthe center-nozzle staging, which has been shown to repeated suppress instability, and right-nozzle staging, which is the case that did not suppress the instability as well in the previous work [22]. In particular, the right nozzle had a higher bifurcation equivalence ratio than the center nozzle, which means that it required more fuel staging than the other four nozzles to adequately suppress instability.…”

Section: Introductionmentioning

confidence: 94%

“…Experiments are conducted in a laboratory-scale fouraround-one multi-nozzle can combustor, shown in Figure 1a, which has been previously described in Refs. [21] and [22]. This combustor confines atmospheric pressure premixed natural gas-air flames anchored to annular swirler nozzles within an optically-accessible 25.4 cm diameter cylindrical quartz chamber with an open, pressure-release boundary condition at the exit.…”

Section: Experimental Configurationmentioning

confidence: 99%

“…Self-excited instability is present at these global equivalence ratios without staging. Instability suppression is achieved when the global equivalence ratio is held constant and staged nozzle equivalence ratio is increased to 0.80 (in the center nozzle) or 0.85 (in the right nozzle); these differences in the staging efficacy were detailed more thoroughly in Culler et al [22]. The fuel staging system enables the equivalence ratio of a selected nozzle to be modified in increments of approximately 0.01.…”

Section: Experimental Configurationmentioning

confidence: 99%

See 4 more Smart Citations

Flame Edge Dynamics and Interaction in a Multinozzle Can Combustor With Fuel Staging

Doleiden

Culler

Tyagi

et al. 2019

Journal of Engineering for Gas Turbines and Power

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The characterization and mitigation of thermoacoustic combustion instabilities in gas turbine engines are necessary to reduce pollutant emissions, premature wear, and component failure associated with unstable flames. Fuel staging, a technique in which the fuel flow to a multinozzle combustor is unevenly distributed between the nozzles, has been shown to mitigate the intensity of self-excited combustion instabilities in multiple nozzle combustors. In our previous work, we hypothesized that staging suppresses instability through a phase-cancelation effect in which the heat release rate from the staged nozzle oscillates out of phase with that of the other nozzles, leading to destructive interference that suppresses the instability. This previous theory, however, was based on chemiluminescence imaging, which is a line-of-sight integrated technique. In this work, we use high-speed laser-induced fluorescence to further investigate instability suppression in two staging configurations: center-nozzle and outer-nozzle staging. An edge-tracking algorithm is used to compute local flame edge displacement as a function of time, allowing instability-driven edge oscillation phase coherence and other instantaneous flame dynamics to be spectrally and spatially resolved. Analysis of flame edge oscillations shows the presence of convecting coherent fluctuations of the flame edge caused by periodic vortex shedding. When the system is unstable, these two flame edges oscillate together as a result of high-intensity longitudinal-mode acoustic oscillations in the combustor that drive periodic vortex shedding at each of the nozzle exits. In the stable cases, however, the phase between the oscillations of the center and outer flame edges is greater than 90 deg (∼114 deg), suggesting that the phase-cancelation hypothesis may be valid. This analysis allows a better understanding of the instantaneous flame dynamics behind flame edge oscillation phase offset and fuel staging-based instability suppression.

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Section: Quantification Of Flame Dynamicsmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 94%

Section: Experimental Configurationmentioning

confidence: 99%

Section: Experimental Configurationmentioning

confidence: 99%

See 3 more Smart Citations

Flame Edge Dynamics and Interaction in a Multinozzle Can Combustor With Fuel Staging

Doleiden

Culler

Tyagi

et al. 2019

Journal of Engineering for Gas Turbines and Power

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Data-driven Detection and Early Prediction of Thermoacoustic Instability in a Multi-nozzle Combustor

Bhattacharya

O’Connor

Ray

2020

Combustion Science and Technology

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Thermoacoustic instability (TAI) is a critical issue in modern lean-burn gas-turbine combustors, which is induced by a strong coupling between the resonant combustor acoustics and fluctuations in the heat release rate. This instability may lead to high-amplitude pressure waves that generate undesirable noise levels as well as fatigue stresses in mechanical structures of the combustor. The intense pressure fluctuations due to TAI may also cause large flow perturbations and possibly flow reversal that may lead to flame oscillations, flame lift-off, and even flame blow-out. Hence, there is a strong need for exercising control actions in a timely fashion to mitigate the TAI phenomena. Anomaly detection is an essential prerequisite to the design of a good controller and such a detector must be able to reliably predict a forthcoming TAI. To detect and predict the onset of a TAI from an ensemble of pressure time-series, this paper investigates three data-driven methods: Fast Fourier transform (FFT), symbolic time series analysis (STSA), and hidden Markov modeling (HMM). The main focus of the paper is to make a comparative evaluation of these three anomaly detection methods for classification of the current regime of operation into stable and unstable categories as well as for real-time identification of precursors to impending instabilities with short-length time series of measured variables (e.g., pressure oscillations). The results, generated on experimental data from a multi-nozzle combustor apparatus, have been compared to evaluate the performance of FFT, STSA, and HMM methods for TAI analysis.

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The Effect of the Degree of Premixedness on Self-Excited Combustion Instability

Howie¹,

Doleiden²,

Peluso³

et al. 2021

Preprint

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The use of lean, premixed fuel and air mixtures is a common strategy to reduce NOx emissions in gas turbine combustors. However, this strategy causes an increased susceptibility to self-excited instability, which manifests as fluctuations in heat release rate, flow velocity, and combustor acoustics that oscillate in-phase in a feedback loop. This study considers the effect of the level of premixedness on the self-excited instability in a single-nozzle combustor. In this system, the fuel can be injected inside the nozzle to create a partially-premixed mixture or far upstream to create a fully-premixed mixture, varying the level of premixedness of the fuel and air entering the combustor. When global equivalence ratio is held constant, the cases with higher levels of premixing have higher instability amplitudes. High-speed CH* chemiluminescence imaging shows that the flame for these cases is more compact and the distribution of the heat release rate oscillations is more concentrated near the corner of the combustor in the outer recirculation zones.Rayleigh index images, which are a metric for quantifying the relative phase of pressure and heat release rate oscillations, suggest that vortex rollup in the corner region is primarily responsible for determining instability characteristics when premixedness is varied. This finding is further supported through analysis of local flame edge dynamics.

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Comparison of Center Nozzle Staging to Outer Nozzle Staging in a Multi-Flame Combustor

Cited by 5 publications

References 17 publications

Flame Edge Dynamics and Interaction in a Multinozzle Can Combustor With Fuel Staging

Flame Edge Dynamics and Interaction in a Multinozzle Can Combustor With Fuel Staging

Data-driven Detection and Early Prediction of Thermoacoustic Instability in a Multi-nozzle Combustor

The Effect of the Degree of Premixedness on Self-Excited Combustion Instability

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