Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Patel, Dipal; Chakraborty, Nilanjan

doi:10.1080/00102202.2016.1214415

Cited by 11 publications

(10 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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%

“…Forced Ignition in different combustion modes has been subject to numerous analyses. A number of previous analyses concentrated on localized forced ignition of inhomogeneous mixtures where the mixture inhomogeneity is characterized by a gradient of mean equivalence ratio [5]. The mixture inhomogeneity can potentially increase the extent of flame wrinkling and may significantly affect the cycle-to-cycle variation of heat release [2,3].…”

Section: Introductionmentioning

confidence: 99%

“…Here, the length scale of mixture inhomogeneity is defined using Taylor micro-scale as  = √6〈[ − 〈〉] 2 〉/〈∇[ − 〈〉] . ∇[ − 〈〉]〉 where angle bracket indicates the global mean evaluated over the whole computational domain [5]. Many previous analyses focused on various aspects of localized forced ignition of both homogenous and inhomogeneous mixture [1], but the effects of on localized forced ignition of a stratified combustible mixture are yet to be analyzed using DNS data [1][2][3]5].…”

Section: Introductionmentioning

confidence: 99%

“…∇[ − 〈〉]〉 where angle bracket indicates the global mean evaluated over the whole computational domain [5]. Many previous analyses focused on various aspects of localized forced ignition of both homogenous and inhomogeneous mixture [1], but the effects of on localized forced ignition of a stratified combustible mixture are yet to be analyzed using DNS data [1][2][3]5]. The availability of detailed experimental data for model development and validation is very limited, and the state of modeling for stratified combustion is less advanced than that for non-premixed or fully premixed combustion.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

Section: Mathematical Background and Numerical Implementationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Self Cite

View full text Add to dashboard Cite

show abstract

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

Turquand

Papapostolou

Chakraborty

2020

Flow Turbulence Combust

View full text Add to dashboard Cite

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.

show abstract

A Numerical Investigation of the Effects of Fuel Composition on the Minimum Ignition Energy for Homogeneous Biogas-Air Mixtures

Papapostolou

Turquand

Chakraborty

2020

Flow Turbulence Combust

Self Cite

View full text Add to dashboard Cite

The minimum ignition energy (MIE) requirements for ensuring successful thermal runaway and self-sustained flame propagation have been analysed for forced ignition of homogeneous stoichiometric biogas-air mixtures for a wide range of initial turbulence intensities and CO2 dilutions using three-dimensional Direct Numerical Simulations under decaying turbulence. The biogas is represented by a CH4 + CO2 mixture and a two-step chemical mechanism involving incomplete oxidation of CH4 to CO and H2O and an equilibrium between the CO oxidation and the CO2 dissociation has been used for simulating biogas-air combustion. It has been found that the MIE increases with increasing CO2 content in the biogas due to the detrimental effect of the CO2 dilution on the burning and heat release rates. The MIE for ensuring self-sustained flame propagation has been found to be greater than the MIE for ensuring only thermal runaway irrespective of its outcome for large root-mean-square (rms) values of turbulent velocity fluctuation, and the MIE values increase with increasing rms turbulent velocity for both cases. It has been found that the MIE values increase more steeply with increasing rms turbulent velocity beyond a critical turbulence intensity than in the case of smaller turbulence intensities. The variations of the normalised MIE (MIE normalised by the value for the quiescent laminar condition) with normalised turbulence intensity for biogas-air mixtures are found to be qualitatively similar to those obtained for the undiluted mixture. However, the critical turbulence intensity has been found to decrease with increasing CO2 dilution. It has been found that the normalised MIE for self-sustained flame propagation increases with increasing rms turbulent velocity following a power-law and the power-law exponent has been found not to vary much with the level of CO2 dilution. This behaviour has been explained using a scaling analysis and flame wrinkling statistics. The stochasticity of the ignition event has been analysed by using different realisations of statistically similar turbulent flow fields for the energy inputs corresponding to the MIE and it has been demonstrated that successful outcomes are obtained in most of the instances, justifying the accuracy of the MIE values identified by this analysis.

show abstract

Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Cited by 11 publications

References 43 publications

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

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

A Numerical Investigation of the Effects of Fuel Composition on the Minimum Ignition Energy for Homogeneous Biogas-Air Mixtures

Contact Info

Product

Resources

About