A Review on Autoignition in Laminar and Turbulent Nonpremixed Flames

Ghai, Sanjeev Kumar; De, Santanu

doi:10.1007/978-981-10-3785-6_2

Cited by 4 publications

(3 citation statements)

References 57 publications

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“…It may be noted that incipient flame formation and extinction may occur more than once before a stable flame is finally established. In this respect, the incipient flames may be identified with the "random spot" generation observed in earlier studies [19]. As in that study the number of random spots prior to a successful autoignition may vary to some extent; however, their statistics such as the mean number of random spots has not been investigated in the present work.…”

Section: Pre-autoignition Behaviormentioning

confidence: 71%

“…Two co-flow air rates are considered i.e., 2 ml/min and 7 ml/min where the higher flow rate is conducive to enhancing turbulence behavior. Four different regimes concerning autoignition have been identified in the literature for non-premixed flames [19]. These have been referred to as "no ignition", "random spots", "flashback", and "lifted flame".…”

Section: Resultsmentioning

confidence: 99%

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Hydrothermal ethanol flames in Co-flow jets

Hicks

Hegde

Kojima

2019

The Journal of Supercritical Fluids

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Results on the autoignition and stabilization of ethanol hydrothermal fames in a Supercritical Water Oxidation (SCWO) reactor operating at constant pressure are reported. The flames are observed as luminous reaction zones occurring in supercritical water; i.e., water at conditions above its critical point (approximately 22 MPa and 374 °C). A co-flow injector is used to inject fuel (inner flow), comprising an aqueous solution ranging from 20 %-v to 50 %-v ethanol, and air (annular flow) into a reactor filled with supercritical water at approximately 24.3 MPa and 425 °C. Results show hydrothermal fames are autoignited and form diffusion flames which exhibit laminar and/or turbulent features depending upon flow conditions. Two orthogonal camera views are used; one providing a backlit shadowgraphic image of the co-flow jet and the other providing color images of the flame. In addition, spectroscopic measurements of flame emissions in the UV and visible spectrum are discussed.

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Section: Pre-autoignition Behaviormentioning

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Hydrothermal ethanol flames in Co-flow jets

Hicks

Hegde

Kojima

2019

The Journal of Supercritical Fluids

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“…Lifted jet diffusion flames (LJDF) have practical applications in industrial burners and combustors, where the flame stabilizes away from the nozzle and thereby minimizes damage to the hardware [1,2]. The lift-off height (LOH) of these flames are highly sensitive to changes in coflow temperature.…”

Section: Introductionmentioning

confidence: 99%

Effects of Partial Premixing and Coflow Temperature on Flame Stabilization of Lifted Jet Flames of Dimethyl Ether in a Vitiated Coflow Based on Stochastic Multiple Mapping Conditioning Approach

Ghai,

Gupta,

2024

Fluids

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The Reynolds-averaged Navier–Stokes (RANS)-based stochastic multiple mapping conditioning (MMC) approach has been used to study partially premixed jet flames of dimethyl ether (DME) introduced into a vitiated coflowing oxidizer stream. This study investigates DME flames with varying degrees of partial premixing within a fuel jet across different coflow temperatures, delving into the underlying flame structure and stabilization mechanisms. Employing a turbulence k-ε model with a customized set of constants, the MMC technique utilizes a mixture fraction as the primary scalar, mapped to the reference variable. Solving a set of ordinary differential equations for the evolution of Lagrangian stochastic particles’ position and composition, the molecular mixing of these particles is executed using the modified Curl’s model. The lift-off height (LOH) derived from RANS-MMC simulations are juxtaposed with experimental data for different degrees of partial premixing of fuel jets and various coflow temperatures. The RANS-MMC methodology adeptly captures LOH for pure DME jets but exhibits an underestimation of flame LOH for partially premixed jet scenarios. Notably, as the degree of premixing escalates, a conspicuous underprediction in LOH becomes apparent. Conditional scatter and contour plots of OH and CH2O unveil that the propagation of partially premixed flames emerges as the dominant mechanism at high coflow temperatures, while autoignition governs flame stabilization at lower coflow temperatures in partially premixed flames. Additionally, for pure DME flames, autoignition remains the primary flame stabilization mechanism across all coflow temperature conditions. The study underscores the importance of considering the degree of premixing in partially premixed jet flames, as it significantly impacts flame stabilization mechanisms and LOH, thereby providing crucial insights into combustion dynamics for various practical applications.

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Numerical investigation of flow and scalar fields of piloted, partially-premixed dimethyl ether/air jet flames using stochastic multiple mapping conditioning approach

Ghai

2019

Combustion and Flame

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A Review on Autoignition in Laminar and Turbulent Nonpremixed Flames

Cited by 4 publications

References 57 publications

Hydrothermal ethanol flames in Co-flow jets

Hydrothermal ethanol flames in Co-flow jets

Effects of Partial Premixing and Coflow Temperature on Flame Stabilization of Lifted Jet Flames of Dimethyl Ether in a Vitiated Coflow Based on Stochastic Multiple Mapping Conditioning Approach

Numerical investigation of flow and scalar fields of piloted, partially-premixed dimethyl ether/air jet flames using stochastic multiple mapping conditioning approach

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