On the phase between pressure and heat release fluctuations for propane/hydrogen flames and its role in mode transitions

Hong, Seunghyuck; Shanbhogue, Santosh J.; Speth, Raymond L.; Ghoniem, Ahmed F.

doi:10.1016/j.combustflame.2013.07.001

Cited by 67 publications

(29 citation statements)

References 38 publications

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“…2. These limits are consistent 2 The pressure amplitude is low as compared to the case of a longer combustor presented in [14,16]. 3 The mechanism of the instability is discussed in our prior studies [14,16].…”

Section: Operating Regimessupporting

confidence: 67%

“…Our prior studies [14,16] demonstrated that the strained consumption speed can be used to collapse the scatter of the mode-transitions observed over a range of mixture compositions and inlet temperatures. In this section, we attempt to correlate the reattachment length with the consumption speed.…”

Section: Correlating the Reattachment Length With The Flame Stabilitymentioning

confidence: 99%

“…The consumption speed is calculated based on characteristic stretch rates of 180−280 s −1 , which are representative of the conditions used in this paper, as documented in detail in Hong et al [14,16]. The thermochemical properties of mixtures are provided by Cantera [19] using the GRI-Mech.…”

Section: Correlating the Reattachment Length With The Flame Stabilitymentioning

confidence: 99%

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Impact of fuel composition on the recirculation zone structure and its role in lean premixed flame anchoring

Hong

Shanbhogue

Ghoniem

2015

Proceedings of the Combustion Institute

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We investigate the dependence of the recirculation zone (RZ) size and structure on the fuel composition using high-speed particle image velocimetry (PIV) and chemiluminescence measurements for C 3 H 8 /H 2 /air lean premixed flames stabilized in a backward-facing step combustor. Results show an intricate coupling between the flame anchoring and the RZ structure and length. For a fixed fuel composition, at relatively low equivalence ratios, the time-averaged RZ is comprised of two counter rotating eddies: a primary eddy (PE) between the shear layer and the bottom wall; and a secondary eddy (SE) between the vertical step wall and the PE. The flame stabilizes downstream of the saddle point of the dividing streamline between the two eddies. As equivalence ratio is raised, the flame moves upstream, pushing the saddle point with it and reducing the size of the SE. Higher temperature of the products reduces the velocity gradient in the shear layer and thus the reattachment length. As equivalence ratio approaches a critical value, the saddle point reaches the step and the SE collapses while the flame starts to exhibit periodic flapping motions, suggesting a correlation between the RZ structure and flame anchoring. The overall trend in the flow field is the same as we add hydrogen to the fuel at a fixed equivalence ratio, demonstrating the impact of fuel composition on the flow field. We show that the reattachment lengths (L R ), which are shown to encapsulate the mean RZ structure, measured over a range of fuel * Corresponding author. 77 Massachusetts Avenue, Room 3-344, Cambridge MA 02139, USA. Fax: +1-617-253-5981. E-mail: ghoniem@mit.edu

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Section: Operating Regimessupporting

confidence: 67%

Section: Correlating the Reattachment Length With The Flame Stabilitymentioning

confidence: 99%

Section: Correlating the Reattachment Length With The Flame Stabilitymentioning

confidence: 99%

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Impact of fuel composition on the recirculation zone structure and its role in lean premixed flame anchoring

Hong

Shanbhogue

Ghoniem

2015

Proceedings of the Combustion Institute

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“…To investigate the cause of the η p variations, we show in figure 7(c,d) the Rayleigh index: RI ≡ 1/T T 0 p (t)q (t) dt, where T is the sampling duration (Lieuwen & Yang 2005). This is used to quantify the magnitude and direction of the energy exchange between the flame and the acoustic modes, accounting not only for the amplitude variations in p (t) and q (t) but also for their phase relationship (Hong et al 2013). The Rayleigh indices of the three main modes (RI * 1 , RI * 2 , RI * f ) are computed by bandpass filtering (±5 Hz) the p (t) and q (t) signals with a zero phase-distortion algorithm based on a forward-backward scheme (Gustafsson 1996).…”

Section: Asynchronous Quenching and Resonant Amplificationmentioning

confidence: 99%

Forced synchronization of quasiperiodic oscillations in a thermoacoustic system

et al. 2019

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In self-excited combustion systems, the application of open-loop forcing is known to be an effective strategy for controlling periodic thermoacoustic oscillations, but it is not known whether and under what conditions such a strategy would work on thermoacoustic oscillations that are not simply periodic. In this study, we experimentally examine the effect of periodic acoustic forcing on a prototypical thermoacoustic system consisting of a ducted laminar premixed flame oscillating quasiperiodically on an ergodic $\mathbb{T}^{2}$ torus at two incommensurate natural frequencies, $f_{1}$ and $f_{2}$. Compared with that of a classical period-1 system, complete synchronization of this $\mathbb{T}_{1,2}^{2}$ system is found to occur via a more intricate route involving three sequential steps: as the forcing amplitude, $\unicode[STIX]{x1D716}_{f}$, increases at a fixed forcing frequency, $f_{f}$, the system transitions first (i) to ergodic $\mathbb{T}_{1,2,f}^{3}$ quasiperiodicity; then (ii) to resonant $\mathbb{T}_{1,f}^{2}$ quasiperiodicity as the weaker of the two natural modes, $f_{2}$, synchronizes first, leading to partial synchronization; and finally (iii) to a $P1_{f}$ limit cycle as the remaining natural mode, $f_{1}$, also synchronizes, leading to complete synchronization. The minimum $\unicode[STIX]{x1D716}_{f}$ required for partial and complete synchronization decreases as $f_{f}$ approaches either $f_{1}$ or $f_{2}$, resulting in two primary Arnold tongues. However, when forced at an amplitude above that required for complete synchronization, the system can transition out of $P1_{f}$ and into $\mathbb{T}_{1,2,f}^{3}$ or $\mathbb{T}_{2,f}^{2}$. The optimal control strategy is to apply off-resonance forcing at a frequency around the weaker natural mode ($f_{2}$) and at an amplitude just sufficient to cause $P1_{f}$, because this produces the largest reduction in thermoacoustic amplitude via asynchronous quenching. Analysis of the Rayleigh index shows that this reduction is physically caused by a disruption of the positive coupling between the unsteady heat release rate of the flame and the $f_{1}$ and $f_{2}$ acoustic modes. If the forcing is applied near the stronger natural mode ($f_{1}$), however, resonant amplification can occur. We then phenomenologically model this $\mathbb{T}_{1,2}^{2}$ thermoacoustic system as two reactively coupled van der Pol oscillators subjected to external sinusoidal forcing, and find that many of its synchronization features – such as the three-step route to $P1_{f}$, the double Arnold tongues, asynchronous quenching and resonant amplification – can be qualitatively reproduced. This shows that these features are not limited to our particular system, but are universal features of forced self-excited oscillators. This study extends the applicability of open-loop control from classical period-1 systems with just a single time scale to ergodic $\mathbb{T}^{2}$ quasiperiodic systems with two incommensurate time scales.

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“…3, we observe two distinct unstable regimes in which the combustor oscillates at two different frequencies, e.g., ∼40 Hz and ∼70 Hz, which are referred to as low-frequency unstable regime and high-frequency unstable regime, respectively. 3 According to the one dimensional acoustic analysis (Hong et al, 2013a), the low-frequency unstable regime (∼40 Hz)…”

Section: Stability Characteristicsmentioning

confidence: 99%

Impact of the Flame-Holder Heat-Transfer Characteristics on the Onset of Combustion Instability

Hong¹,

Shanbhogue²,

Kedia³

et al. 2013

Combustion Science and Technology

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In this paper, we investigate the impact of heat transfer between the flame and the flameholder on the dynamic stability characteristics of a 50-kW backward facing step combustor.We conducted a series of tests where two backward step blocks were used, made of ceramic and stainless steel whose thermal conductivities are 1.06 and 12 W/m/K, respectively. Stability characteristics of the two flame-holder materials were examined using measurements of the dynamic pressure and flame chemiluminescence over a range of operating conditions.Results show that with the ceramic flame-holder, the onset of instability is significantly delayed in time and, for certain operating conditions, disappears altogether, whereas with the higher conductivity material, the combustor becomes increasingly unstable over a range of operating conditions. We explain these trends using the heat flux through the flame-holder and the change in the burning velocity near the step wall. Results suggest a potential approach of using low thermal conductivity material near the flame-holder as passive dynamics suppression methods.

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On the phase between pressure and heat release fluctuations for propane/hydrogen flames and its role in mode transitions

Cited by 67 publications

References 38 publications

Impact of fuel composition on the recirculation zone structure and its role in lean premixed flame anchoring

Impact of fuel composition on the recirculation zone structure and its role in lean premixed flame anchoring

Forced synchronization of quasiperiodic oscillations in a thermoacoustic system

Impact of the Flame-Holder Heat-Transfer Characteristics on the Onset of Combustion Instability

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