Effects of Energy Deposition Characteristics on Localised Forced Ignition of Homogeneous Mixtures

Patel, Dipal; Chakraborty, Nilanjan

doi:10.1260/1756-8277.7.2.151

Cited by 15 publications

(45 citation statements)

References 41 publications

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“…Moreover, an increase in R for a given set of values of a sp and b sp leads to deposition of same amount of ignition energy over a large volume (and mass) of gas and thus reduces the probability of finding large values of temperature, which in turn has detrimental effects on the success of ignition and subsequent sustenance of the flame. The effects of R, a sp and b sp on localised forced ignition for homogeneous mixtures have been addressed elsewhere [38] and similar qualitative effects can also be expected for stratified mixture combustion.…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 58%

Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation

Patel

Chakraborty

2016

Flow Turbulence Combust

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The influences of fuel Lewis number Le F on localised forced ignition of globally stoichiometric stratified mixtures have been analysed using three-dimensional compressible Direct Numerical Simulations (DNS) for cases with Le F ranging from 0.8 to 1.2. The globally stoichiometric stratified mixtures with different values of root-mean-square (rms) equivalence ratio fluctuation (i.e. φ = 0.2, 0.4 and 0.6) and the Taylor micro-scale l φ of equivalence ratio φ variation (i.e. l φ /l f = 2.1, 5.5 and 8.3 with l f being the Zel'dovich flame thickness of the stoichiometric laminar premixed flame) have been considered for different initial rms values of turbulent velocity u . A pseudo-spectral method is used to initialise the equivalence ratio variation following a presumed bi-modal distribution for prescribed values of φ and l φ /l f for global mean equivalence ratio φ = 1.0. The localised ignition is accounted for by a source term in the energy transport equation that deposits energy for a stipulated time interval. It has been observed that the maximum values of temperature and the fuel reaction rate magnitude increase with decreasing Le F during the period of external energy deposition. The initial values of Le F , u /S b(φ=1)

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Section: Mathematical Background and Numerical Implementationmentioning

confidence: 58%

Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation

Patel

Chakraborty

2016

Flow Turbulence Combust

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“…The chemical mechanism is simplified here by single step chemical reaction [6], which takes the form of ( + [5,7] where and are the fuel mass fractions in the unburned and burned gases respectively.…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

“…where is the radial direction from the center of the ignitor, is the width of the Gaussian profile and the constant can be determined by following volume integration as, ̇= ∫ ′′′ , where ̇ is the ignition power, which is defined as [5,7,8]:…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

“…The parameter can be expressed as = , where is the energy deposition duration parameter and = / ( = 1) is the characteristic chemical time scale. For the present analysis = 0.2 and ≈ 1.55 are taken following previous studies [5,7,8] to ensure successful ignition and Lewis number of all species is taken to be unity. The pseudo-spectral method proposed by Eswaran and Pope was used for generating initial  distribution following bi-modal distribution [9].…”

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

“…The temporal evolution of the burned gas mass normalized with the mass of an unburned gas sphere with a radius equal to (i.e. = [ ( ≥0.9) ]/[(4/3) 3 ]) [5,7,8] for all the cases listed in Table are shown for the cases WF and CF as compare to TR, because of eddy thermal diffusivity ~′ 11 , thereby chemical heat release overcomes the heat transfer for lower value of number. Figure 3 reveals that in the case 24TRA does not rise with time as compared to other.…”

Section: Extent Of Burningmentioning

confidence: 99%

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Effects of Combustion Regimes on Localized Forced Ignition of Turbulent Stratified Mixture

Modi¹,

Uchil²,

Patel³

2019

Proceedings of the 4th World Congress on Momentum, Heat and Mass Transfer

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Localized forced ignition of turbulent stratified mixtures (〈〉 = 1,  ′ = 0.2) with different values of mixture inhomogeneity has been analyzed based on Direct Numerical Simulations (DNS) for different values of Karlovitz number () corresponding to the premixed turbulent combustion regime diagram. The initial values of turbulent fluctuations (i.e. '/ ( = 1)) and the integral length scale of turbulence (i.e. 11 /) have been modified to bring about the change in. The localized ignition is accounted by a source term in the energy transport equation which deposits energy over a specified time interval. It has been found that combustion takes place predominantly under a premixed mode of combustion following successful ignition. The percentage of heat release due to a premixed mode of combustion increases with increasing due to high mixing rate. An increase in has been shown to have adverse effects on the burned gas mass. The different level of mixture inhomogeneity shown to have favorable effect with increasing for sustaining combustion. Furthermore, a stratified combustion mixture has been found to be a more favorable choice over homogeneous mixtures for a given turbulent flow condition for sustaining combustion.

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Effects of Biogas Composition on the Edge Flame Propagation in Igniting Turbulent Mixing Layers

Turquand

Papapostolou

Chakraborty

2020

Flow Turbulence Combust

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Three-dimensional compressible Direct Numerical Simulations have been used to investigate the localised forced ignition of statistically planar biogas/air mixing layers for different levels of turbulence intensity and biogas composition. The biogas is represented by a $$\hbox {CH}_4$$ CH 4 /$$\hbox {CO}_2$$ CO 2 mixture and a two-step mechanism capturing the variation of the unstrained laminar flame speed with equivalence ratio and $$\hbox {CO}_2$$ CO 2 dilution was used. The mixture composition was found to significantly affect the flame kernel development which was reflected in the diminished growth rate of the burned gas volume with increasing $$\hbox {CO}_2$$ CO 2 dilution. A successful ignition of $$\hbox {CH}_4$$ CH 4 /$$\hbox {CO}_2$$ CO 2 /air mixing layer gives rise to a tribrachial flame structure involving fuel-rich and lean premixed branches on either side of the diffusion flame stabilised on the stoichiometric mixture fraction iso-surface. The most probable edge flame speed decreases in time and converges to a value that is at most equal to its laminar theoretical limit, and can even locally become negative for large values of the dilution and/or turbulence intensity. The decomposition of the edge flame speed showed a negligible or negative contribution of the mixture fraction surface displacement speed, while the displacement speed of the fuel mass fraction surface appeared as the dominant contributor. Finally, the edge flame speed dependences to the fuel mass fraction and mixture fraction gradients, fuel mass fraction iso-surface curvature and tangential strain rate have been analysed and found, within the dilution values considered, qualitatively similar to those of undiluted mixtures regardless of the amount of $$\hbox {CO}_2$$ CO 2 , although quantitative differences were observed.

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Effects of Energy Deposition Characteristics on Localised Forced Ignition of Homogeneous Mixtures

Cited by 15 publications

References 41 publications

Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation

Effects of Fuel Lewis Number on Localised Forced Ignition of Globally Stoichiometric Stratified Mixtures: a Numerical Investigation

Effects of Combustion Regimes on Localized Forced Ignition of Turbulent Stratified Mixture

Effects of Biogas Composition on the Edge Flame Propagation in Igniting Turbulent Mixing Layers

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