Autoignition in a non-premixed medium: DNS studies on the effects of three-dimensional turbulence

Sreedhara, S.; Lakshmisha, K.N.

doi:10.1016/s1540-7489(02)80250-4

Cited by 80 publications

(38 citation statements)

References 23 publications

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“…But more importantly, the source terms just outside of the ignition kernel is also much higher than the diffusion term at the ignited region, which means that the non-ignited neighboring regions will autoignite later on, rather than the initial ignition kernel would trigger them to ignite. In addition, the trend of the source term almost coincides with the Z MR curve, indicating that the autoignition occurs around Z MR , as mentioned in the literature [19,33,37]. In Figs.…”

Section: Ignition and Flame Characteristicssupporting

confidence: 76%

3D DNS of MILD combustion: A detailed analysis of heat loss effects, preferential diffusion, and flame formation mechanisms

Goktolga

Oijen

Goey

2015

Fuel

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Section: Ignition and Flame Characteristicssupporting

confidence: 76%

3D DNS of MILD combustion: A detailed analysis of heat loss effects, preferential diffusion, and flame formation mechanisms

Goktolga

Oijen

Goey

2015

Fuel

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“…High initial value of u enhances the appearance of ξ MR and eventually creates well-mixed spots with reduced gradient (χ |ξ MR ), with the overall effect of increasing the probability of autoignition. These conclusions were extended in later work by Im et al [2], Sreedhara and Lakshmisha [3] and Echekki and Chen [4] using more realistic chemistry and a three-dimensional flow field. More recently Wang and Rutland [5] performed DNS of an autoigniting spray jet.…”

supporting

confidence: 55%

Second-Order Conditional Moment Closure Simulations of Autoignition of an n-heptane Plume in a Turbulent Coflow of Heated Air

Paola

Kim

Mastorakos

2008

Flow Turbulence Combust

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Autoignition of an n-heptane plume in a turbulent coflow of heated air has been studied using the conditional moment closure (CMC) method with a secondorder closure for the conditional chemical source term. Two different methodologies have been considered: (i) the Taylor expansion method, in which the second order correction was based on the solution of the full covariance matrix for the 31 reactive species in the chemical mechanism and hence was not limited to a few selected reactions, and (ii) the conditional PDF method, in which only the temperature conditional variance equation has been solved and its PDF assumed to be a β-function. The results compare favorably with experiment in terms of autoignition location. The structure of the reaction zone in mixture fraction space has been explored. The relative performance of the two methodologies is discussed.

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“…Earlier investigations of methane issuing in hot vitiated co-flows, revealed the existence of "kernels" that develop at some distance downstream of the jet exit plane and travel further downstream to initiate flaming combustion [2]. This scenario for the auto-ignition of gaseous flames has been confirmed by both large eddy simulations (LES) [7] as well as direct numerical simulations (DNS) [8][9][10][11][12] which also indicate that the dominant radicals in these kernels are CH 2 O in methane fuels and HO 2 in hydrogen fuels. These DNS studies also reinforced the concept of ignition being initiated at the most reactive mixture fraction, ξ MR [9,13].…”

Section: Introductionmentioning

confidence: 73%

The Structure of the Auto-Ignition Region of Turbulent Dilute Methanol Sprays Issuing in a Vitiated Co-flow

O'Loughlin

Masri

2012

Flow Turbulence Combust

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This paper presents planar imaging of laser induced fluorescence (LIF) from key reactive species in the auto-ignition region of dilute turbulent spray flames of methanol. High-speed (5 kHz) LIF-OH imaging as well as low speed (10 Hz) imaging of joint LIF-OH-CH 2 O is performed. The product of the OH and CH 2 O signals is used as a qualitative indicator of local heat release. The burner is kept intentionally simple to facilitate computations and the spray is formed upstream of the jet exit plane and carried with air or nitrogen into a hot co-flowing stream of vitiated combustion products. The studied flames are all lifted but differ in the shape of their leading edge and heat release zones. Similarities with auto-ignition of gaseous fuels, as well as differences, are noted here. Formaldehyde is detected earlier than OH implying that the former is a key precursor in the initiation of auto-ignition. Growing kernels of OH that are advected from upstream, close in on the jet centreline and ignite the main flame. The existence of double reaction zones in some flames may be due to ignitable mixtures formed subsequent to local evaporation of droplets and subsequent mixing. When air is used as spray carrier, reaction zones broaden with distance, possibly due to increased partial premixing and regions of intense heat release occur near the flame centreline further downstream. With nitrogen as carrier, the flame maintains a nominal diffusion-like structure with reaction zones of uniform width and substantially less concentration of heat release on the flame centreline.

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Autoignition in a non-premixed medium: DNS studies on the effects of three-dimensional turbulence

Cited by 80 publications

References 23 publications

3D DNS of MILD combustion: A detailed analysis of heat loss effects, preferential diffusion, and flame formation mechanisms

3D DNS of MILD combustion: A detailed analysis of heat loss effects, preferential diffusion, and flame formation mechanisms

Second-Order Conditional Moment Closure Simulations of Autoignition of an n-heptane Plume in a Turbulent Coflow of Heated Air

The Structure of the Auto-Ignition Region of Turbulent Dilute Methanol Sprays Issuing in a Vitiated Co-flow

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