Dynamics of FREI with/without cool flame interaction

Akita, Keisuke; Morii, Youhi; Murakami, Yuki; Nakamura, Hisashi; Tezuka, T.; Maruta, Kaoru

doi:10.1016/j.proci.2022.07.206

Cited by 9 publications

(5 citation statements)

References 36 publications

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“…Furthermore, the wider the channel, the longer it takes for the flame to extinguish, thus diminishing the FREI frequency. These results confirm the findings of similar studies for methane/air combustion [22,40].…”

Section: Impact Of Channel Width On Frei Characteristicssupporting

confidence: 92%

“…It should be noted that using HRR T for the ignition phenomenon analyses is a more common approach in the literature than using the axial temperature [18,22,28,34,36]; however, in the present work, the HRR T data were not directly implemented, as they typically produce noisy curves, which cannot be utilized to define such time-sensitive properties. Such noise is primarily attributed to the numerical artifacts resulting from the computational analysis; therefore, a smoothened HRR T data trace was plotted against the axial temperature to validate our approach and to make sure that the axial temperature data are technically supported and can be used as a metric to predict the ignition properties and the flame characteristics.…”

Section: Ignition Metrics: Time Location and Spanmentioning

confidence: 99%

“…It has been shown that cool flames are usually generated in the unburned fuel mixture region, while another conventional flame propagates through the reacting mixture. Such a phenomenon is referred to as autoignition-assisted flame propagation [22]. Pizza et al [23] studied the dynamics of fuel-lean premixed hydrogen/air flames in microchannels using three-dimensional (3D) numerical simulations, and observed that various flame modes depend on the inlet flow velocity and the channel size.…”

Section: Introductionmentioning

confidence: 99%

“…The extinction-to-ignition time: defined as the time duration from the extinction time to the ignition time of the subsequent cycle [22].…”

mentioning

confidence: 99%

See 3 more Smart Citations

Investigating the Ignition and Stability Limits of Premixed Methane/Air Combustion in Micro-Channels

Kutkut,

Ayoobi,

Baumgardner

et al. 2023

Energies

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Understanding and improving the performance of miniature devices powered by micro-combustion have been the focus of continued attention of researchers recently. The goal of the present work is to investigate the behavior of premixed methane–air combustion in a quartz microreactor with an externally controlled wall temperature. Specifically, the impacts of the flow inlet velocity, the equivalence ratio, and the microreactor channel size are examined. This study is conducted by means of computational simulations, and the results are validated against prior experimental data, as well as by other similar studies in the literature. Utilizing simulation results with detailed chemistry, the present work provides more in-depth insight into a variety of phenomena, such as ignition, flame propagation, flames with repetitive extinctions and ignitions (FREI), and flame stabilization. In particular, the ignition, the flame span, and the FREI-related characteristics are scrutinized to understand the underlying physics of the flame stability/instability modes. It is shown that the flames appear stable at higher inlet velocities, while the FREI mode is detected at a lower inlet velocity, depending on the equivalence ratio and the channel size. The findings also explain how different operating conditions impact the flame characteristics in both stability modes.

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Section: Impact Of Channel Width On Frei Characteristicssupporting

confidence: 92%

Section: Ignition Metrics: Time Location and Spanmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The extinction-to-ignition time: defined as the time duration from the extinction time to the ignition time of the subsequent cycle [22].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Investigating the Ignition and Stability Limits of Premixed Methane/Air Combustion in Micro-Channels

Kutkut,

Ayoobi,

Baumgardner

et al. 2023

Energies

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show abstract

“…The hot flame propagation speed increased and decreased, but was accelerated again downstream due to the effects of the stable cool flame. Akita et al [74] also studied the effect of the diameter of quartz tubes and inlet flow velocity on the behaviour of flames in a micro flow reactor with a controlled temperature profile (MFR). Figure 58 shows the photographs of weak flames and FREI in an MFR with different diameters.…”

Section: Instabilities For Liquid Fuel Combustion At Small Scalementioning

confidence: 99%

Towards the Development of Miniature Scale Liquid Fuel Combustors for Power Generation Application—A Review

Sankar,

Sudarsanan,

Mukhopadhyay

et al. 2023

Energies

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As the demand for powerful, light energy sources continues to grow, traditional electrochemical batteries are no longer sufficient and combustion-based power generation devices have become an attractive alternative due to their high energy density, compact size, fast recharging time and long service life. While most research on miniature-scale combustors has focused on gaseous fuels, the use of commonly available liquid fuels has the potential to be highly portable and economical. However, the complexity of droplet atomization, evaporation, mixing and burning in a limited volume and short residence time has presented significant challenges for researchers. This review focuses on various methodologies proposed by researchers (like flow burring injector, fuel film injection, injecting into porous media, electrospray and some self-aspirating designs) to overcome these challenges, the combustion behaviour and different instabilities associated with liquid fuels at small scales. The current review intends to present a clear direction to channel the efforts made by researchers to overcome the difficulties associated with liquid fuel combustion at small scales for power generation applications. Additionally, this review aims to give an overview of power systems at the micro and meso scales that operate using liquid fuels. The methodologies introduced like electrospray requires external power, which again makes the system complex. Towards the development of standalone type power generators, the self-aspirating design which makes use of hydrostatic pressure, fuel film injection or taking advantage of exhaust gas enthalpy to preheat and evaporate the liquid fuel are the promising methodologies.

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Effects of unburnt reaction progress on stretch flame dynamics under elevated temperatures

Akita,

Zhao,

Morii

et al. 2024

Combustion and Flame

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Dynamics of FREI with/without cool flame interaction

Cited by 9 publications

References 36 publications

Investigating the Ignition and Stability Limits of Premixed Methane/Air Combustion in Micro-Channels

Investigating the Ignition and Stability Limits of Premixed Methane/Air Combustion in Micro-Channels

Towards the Development of Miniature Scale Liquid Fuel Combustors for Power Generation Application—A Review

Effects of unburnt reaction progress on stretch flame dynamics under elevated temperatures

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